JP6750377B2 - Lead acid battery - Google Patents

Description

The present invention relates to a lead storage battery.

Lead acid batteries are used in various applications such as in-vehicle and industrial applications. The lead storage battery includes a negative electrode plate, a positive electrode plate, and an electrolytic solution. A separator is arranged between the negative electrode plate and the positive electrode plate. As the separator, a non-woven fabric of glass fiber or the like is used. The negative electrode plate includes a negative electrode current collector and a negative electrode material.

The negative electrode material contains an active material (lead or lead sulfate) that exhibits a capacity by a redox reaction. In the negative electrode plate, a lead sulfate reduction reaction proceeds during charging, but lead sulfate is less likely to be reduced to spongy lead. As a result, lead sulfate accumulates, the sulfation in which lead sulfate crystals gradually grow, and the life performance of the lead storage battery decreases. A shrink-proofing agent (expander) is added to the negative electrode plate for the purpose of suppressing lead sulfate accumulation. Above all, the anti-shrink agent derived from an organic substance is called an organic anti-shrink agent.

In a stationary lead-acid battery, lignin or lignosulfonic acid derived from a natural product has been added to the negative electrode as an organic shrink-proofing agent, and a glass fiber nonwoven fabric has been used as a separator.

In lead-acid batteries, the use of synthetic organic shrinkage inhibitors has also been proposed. Patent Document 1 teaches that an organic shrinkage inhibitor having a sulfur element content of 4000 to 6000 μmol/g is used from the viewpoint of low-temperature high-rate discharge performance.

Patent Document 2 teaches that a bisphenol A/sodium aminobenzene sulfonate/formaldehyde condensate having a sulfur content of 6 to 11 mass% in the compound is added to the negative electrode plate. Further, in Patent Document 2, it is proposed to use a non-woven fabric made by making glass fiber, synthetic pulp, and silica powder in water as a separator of a lead storage battery.

International publication 2015/181865 pamphlet International Publication No. 2012/157311 Pamphlet

In a lead acid battery, even if a natural lignin or a synthetic organic shrink proof agent is combined with a separator made of a non-woven glass fiber, it is difficult to suppress lead sulfate accumulation and sufficient life performance cannot be obtained. Further, a part of the organic shrink-proofing agent added to the negative electrode plate tends to be eluted in the electrolytic solution to soften the positive electrode material. When the positive electrode material is softened, the durability of the positive electrode plate is reduced, and the positive electrode material is likely to drop from the positive electrode current collector. Such deterioration of the positive electrode plate reduces the life performance of the lead storage battery.

One aspect of the present invention includes a negative electrode plate, a positive electrode plate, a separator interposed between the negative electrode plate and the positive electrode plate, and an electrolytic solution,
The negative electrode plate includes a negative electrode current collector and a negative electrode material,
The negative electrode material contains an organic shrinkage inhibitor containing elemental sulfur,
The content of the elemental sulfur in the organic anti-shrink agent is more than 3000 μmol/g and not more than 9000 μmol/g,
The separator includes a non-woven fabric containing glass fibers and silica particles attached to the glass fibers,
The present invention relates to a lead storage battery in which the average particle size of the silica particles is 1 to 10 μm.

According to the present invention, the life performance of a lead storage battery can be improved.

It is a perspective view which shows typically the state which removed the lid of the lead acid battery which concerns on one side of this invention. It is a front view of the lead acid battery of FIG. FIG. 2B is a sectional view taken along line IIB-IIB of the lead storage battery in FIG. 2A. It is a graph which shows the relationship between the content of the sulfur element of an organic shrink-proofing agent and the life cycle of a lead acid battery when a separator contains a silica particle, and does not contain it. It is a graph which shows the relationship between the average particle diameter of the silica particles in a separator, and the life cycle of a lead acid battery. 6 is a graph showing the relationship between the sulfur element content of the organic shrink-proofing agent and the elution amount of the organic shrink-proofing agent when the separator contains silica particles and when the separator does not contain silica particles. It is a graph which shows the relationship between the content of the elemental sulfur of the organic shrink-proofing agent and the specific resistance of the negative electrode material when the separator does not contain silica particles. 6 is a graph showing the relationship between the content of elemental sulfur in the organic shrink-proofing agent and the amount of lead sulfate accumulated in the lower portion of the negative electrode when the separator does not contain silica particles.

A lead-acid battery according to one aspect of the present invention includes a negative electrode plate, a positive electrode plate, a separator interposed between the negative electrode plate and the positive electrode plate, and an electrolytic solution. The negative electrode plate includes a negative electrode current collector and a negative electrode material. The negative electrode material contains an organic anti-shrink agent containing a sulfur element, and the content of the sulfur element in the organic anti-shrink agent is more than 3000 μmol/g and 9000 μmol/g or less. The separator includes a non-woven fabric including glass fibers and silica particles attached to the glass fibers. The average particle diameter of the silica particles is 1 to 10 μm.

Conventionally, in a stationary lead-acid battery, lignin or lignosulfonic acid (hereinafter referred to as lignin) derived from a natural product has been used as an organic shrink proof agent, and a non-woven fabric of glass fiber has been used as a separator. The content of elemental sulfur contained in lignin is usually 500 to 600 μmol/g. However, it is difficult to sufficiently suppress lead sulfate accumulation in the negative electrode plate. Sulfuric acid ions are generated in the vicinity of the electrode plate during charging, and the sulfuric acid solution with high specific gravity is partially generated, so that the sulfuric acid solution with high specific gravity tends to settle and stay in the lower part of the battery case. Is particularly remarkable in the lower region of the negative electrode plate. Also, the use of an organic anti-shrink agent having a content of elemental sulfur of more than 3000 μmol/g has been studied. However, when such an organic anti-shrink agent containing a large amount of sulfur element is added to the negative electrode plate, the elution of the organic anti-shrink agent from the negative electrode plate becomes remarkable, and the positive electrode material is softened by the action of the eluted organic anti-shrink agent. To do. Therefore, in the conventional lead storage battery, it is difficult to obtain sufficient life performance due to the accumulation of lead sulfate in the lower region of the negative electrode plate or the softening of the positive electrode material.

On the other hand, in the lead-acid battery according to one aspect of the present invention, the content of the sulfur element is more than 3000 μmol/g and not more than 9000 μmol/g, and the glass fiber and the average particle diameter attached to the glass fiber. And a separator including a nonwoven fabric containing silica particles of 1 to 10 μm. Such a combination suppresses lead sulfate accumulation in the lower region of the negative electrode plate. Further, although an organic shrinkage inhibitor having a sulfur content of more than 3000 μmol/g and not more than 9000 μmol/g is used, the elution of the organic shrinkage inhibitor from the negative electrode plate is suppressed, and thus the softening of the positive electrode material is also suppressed. It Therefore, life performance can be improved.

Such an effect is considered to be due to the fact that the silica particles having the above-mentioned average particle diameter are contained in the separator, so that the electrolytic solution is appropriately gelled around the separator, and the fluidity of the electrolytic solution is lowered. .. When the fluidity of the electrolyte decreases, the precipitation of sulfuric acid solution with high specific gravity is suppressed, the elution of the organic anti-shrink agent from the negative electrode plate is suppressed, and the migration of the organic anti-shrink agent is suppressed even if the organic anti-shrink agent is eluted. To be done. Further, in the separator, since the silica particles are in a state of entering between the glass fibers, the movement of the glass fibers is suppressed and the strength of the separator is improved. It is considered that the improvement of the separator strength also suppresses the elution of the organic anti-shrink agent from the negative electrode plate.

When the average particle size of the silica particles contained in the separator is less than 1 μm, the internal resistance of the lead storage battery increases and the life performance decreases. When the average particle diameter of the silica particles is more than 10 μm, the effect of lowering the fluidity of the electrolytic solution becomes low, and the softening or dropping of the positive electrode material cannot be suppressed, so that the life performance is impaired. From the viewpoint of easily obtaining high life performance, the average particle diameter of the silica particles is preferably 1 to 5 μm, and more preferably 1 to 4 μm.

The average particle size of the silica particles can be determined, for example, by arbitrarily selecting 10 or more silica particles in an enlarged photograph of the separator and averaging the particle sizes of the selected particles. The particle size of the silica particles is the diameter of an equivalent circle having the same area as the projected area of the silica particles that can be confirmed in the enlarged photograph.

The organic anti-shrink agent used in the lead storage battery according to the present embodiment contains elemental sulfur at a ratio of more than 3000 μmol/g and not more than 9000 μmol/g. From the viewpoint of further improving the life characteristics, the content of the sulfur element in the organic shrink-proofing agent is preferably 3500 to 9000 μmol/g, more preferably 4000 to 9000 μmol/g, and 5000 to 9000 μmol/g or 5000 to 8000 μmol/g. Particularly preferred.
The content of elemental sulfur in the organic anti-shrink agent is X μmol/g, which means that the content of elemental sulfur contained in 1 g of the organic anti-shrink agent is X μmol.

The lead acid battery according to one aspect of the present invention is particularly suitable for a control valve type (sealed type) lead acid battery. The lead storage battery according to the present embodiment can be used as, for example, a lead storage battery for automobiles, a lead storage battery for stationary uninterruptible power supplies, a lead storage battery for industrial vehicles such as forklifts, and the like.

The density of the negative electrode material is, for example, 2.5 to 5 g/cm ³ . From the viewpoint of obtaining higher life performance, the density of the negative electrode material is preferably 2.5 to 4.5 g/cm ³ . When the density of the negative electrode material is 2.5 to 4.5 g/cm ³ , use of an organic shrink proofing agent having a sulfur element content of 6000 μmol/g or more makes it easy to obtain high life performance. Further, from the viewpoint of life performance, when the content of the sulfur element of the organic anti-shrink agent exceeds 3000 μmol/g (preferably 4000 μmol/g or more), the density of the negative electrode material is 3.5 to 4.5 g. /Cm ³ , preferably 3.0 to 4.5 g/cm ³ when the sulfur element content of the organic anti-shrink agent is 5000 μmol/g or more. When the density of the negative electrode material is set to 2.5 to 3.5 g/cm ³ , in addition to being advantageous from the viewpoint of weight reduction, the content of sulfur element is 6000 μmol/g or more (preferably 7000 μmol/g). When the organic shrinkage inhibitor described above) is used, the effect of suppressing the specific resistance of the negative electrode material and the accumulation of lead sulfate on the negative electrode plate becomes remarkable.

Hereinafter, the lead storage battery according to one aspect of the present invention will be described for each main constituent element, but the present invention is not limited to the following embodiments.
(Negative electrode plate)
The negative electrode plate of the lead storage battery is composed of a negative electrode current collector and a negative electrode material. The negative electrode material is obtained by removing the negative electrode current collector from the negative electrode plate. The negative electrode current collector may be formed by casting lead (Pb) or a lead alloy, or may be formed by processing a lead or lead alloy sheet. Examples of the processing method include expanding processing and punching processing.

The lead alloy used for the current collector may be any of a Pb-Sb-based alloy, a Pb-Ca-based alloy, and a Pb-Ca-Sn-based alloy. These lead or lead alloy may further contain, as an additional element, at least one selected from the group consisting of Ba, Ag, Al, Bi, As, Se and Cu. The negative electrode current collector may have a plurality of lead alloy layers having different compositions.

The negative electrode material has a predetermined content of a negative electrode active material (lead or lead sulfate) that exhibits a capacity by a redox reaction, and an organic shrink proofing agent containing sulfur element in excess of 3000 μmol/g and 9000 μmo/g or less. Including. The negative electrode material may further contain a carbonaceous material such as carbon black, barium sulfate, etc., and may further contain other additives as necessary.

The negative electrode active material in the charged state is spongy lead, but the unformed negative electrode plate is usually produced by using lead powder.

The organic anti-shrink agent is an organic polymer containing elemental sulfur, and generally contains a plurality of aromatic rings in the molecule and also contains elemental sulfur as a sulfur-containing group. Among the sulfur-containing groups, sulfonic acid groups or sulfonyl groups, which are stable forms, are preferable. The sulfonic acid group may be present in an acid form or in a salt form such as Na salt.

As a specific example of the organic anti-shrink agent, a condensation product of a compound having a sulfur-containing group and an aromatic ring with formaldehyde is preferable. The compound may have a plurality of aromatic rings. Examples of the aromatic ring include a benzene ring and a naphthalene ring. When the compound having an aromatic ring has a plurality of aromatic rings, the plurality of aromatic rings may be linked by a direct bond or a linking group (for example, an alkylene group, a sulfone group, etc.). Examples of such a structure include biphenyl, bisphenylalkane, and bisphenylsulfone. Examples of the compound having an aromatic ring include compounds having the above aromatic ring and a hydroxy group and/or an amino group. The hydroxy group or amino group may be directly bonded to the aromatic ring, or may be bonded as an alkyl chain having a hydroxy group or amino group. The compound having an aromatic ring is preferably a bisphenol compound, a hydroxybiphenyl compound, a hydroxynaphthalene compound, a phenol compound or the like. The compound having an aromatic ring may further have a substituent. The organic anti-shrink agent may contain one kind of the residue of these compounds or plural kinds thereof. As the bisphenol compound, bisphenol A, bisphenol S, bisphenol F and the like are preferable. Among them, bisphenol S has a sulfonyl group (—SO ₂ —), so that it is easy to increase the content of elemental sulfur. The bisphenol compound condensate is suitable for a lead storage battery that is placed in an environment at a temperature higher than room temperature, because the starting performance at a low temperature is not impaired even when the environment is higher than room temperature.

The sulfur-containing group may be directly bonded to the aromatic ring contained in the compound, for example, it may be bonded to the aromatic ring as an alkyl chain having a sulfur-containing group. Further, for example, a monocyclic aromatic compound such as aminobenzenesulfonic acid or alkylaminobenzenesulfonic acid may be condensed with formaldehyde together with the above-mentioned compound having an aromatic ring.

Organic compounds such as N,N′-(sulfonyldi-4,1-phenylene)bis(1,2,3,4-tetrahydro-6-methyl-2,4-dioxopyrimidine-5-sulfonamide) condensate You may use as a shrinkproofing agent.

The content of the organic anti-shrink agent contained in the negative electrode material does not greatly affect the action of the organic anti-shrink agent within the general range. The content of the organic anti-shrink agent contained in the negative electrode material is, for example, preferably 0.01% by mass or more, more preferably 0.02% by mass or more, further preferably 0.05% by mass or more, while 1.0 The content is preferably not more than mass%, more preferably not more than 0.8 mass%, further preferably not more than 0.3 mass%. Here, the content of the organic anti-shrink agent contained in the negative electrode material is the content in the negative electrode material obtained by the method described later from the already-formed fully charged lead storage battery.

The negative electrode plate can be formed by filling a negative electrode current collector with a negative electrode paste, aging and drying to produce an unformed negative electrode plate, and then forming an unformed negative electrode plate. The negative electrode paste is prepared by adding water and sulfuric acid to lead powder, an organic shrink-proofing agent and, if necessary, various additives and kneading. In the aging step, it is preferable to age the unformed negative electrode plate at a temperature higher than room temperature and a high humidity.

The formation can be performed by charging the electrode plate group in a state where the electrode plate group including the unformed negative electrode plate is immersed in the electrolytic solution containing sulfuric acid in the battery case of the lead storage battery. However, the formation may be performed before the lead storage battery or the electrode plate group is assembled. By formation, spongy lead is produced.

(Positive electrode)
As the positive electrode plate of the lead storage battery, it is preferable to use a paste type positive electrode plate.
The paste-type positive electrode plate includes a positive electrode current collector and a positive electrode material. The positive electrode material is held on the positive electrode current collector. The positive electrode current collector may be formed in the same manner as the negative electrode current collector, and may be formed by casting lead or a lead alloy or processing a lead or lead alloy sheet.

The lead alloy used for the positive electrode current collector is preferably a Pb-Ca-based alloy or a Pb-Ca-Sn-based alloy from the viewpoint of corrosion resistance and mechanical strength. The positive electrode current collector may have lead alloy layers having different compositions, and may have a plurality of lead alloy layers.
The positive electrode material contains a positive electrode active material (lead dioxide or lead sulfate) that develops capacity by a redox reaction. The positive electrode material may contain other additives as required.

The unformed paste-type positive electrode plate is obtained by filling the positive electrode current collector with the positive electrode paste, aging and drying, as in the case of the negative electrode plate. After that, an unformed positive electrode plate is formed. The positive electrode paste is prepared by kneading lead powder, additives, water and sulfuric acid.

(Separator)
The non-woven fabric forming the separator is a mat in which glass fibers are entwined without being woven, and silica particles having an average particle diameter of 1 to 10 μm are attached to the glass fibers. Such a non-woven fabric can be obtained, for example, by paper-making (wet paper making, etc.) glass fibers and silica particles.

The average fiber diameter of the glass fibers is preferably 0.1 μm or more and 25 μm or less. The average fiber diameter can be determined from an enlarged photograph of the selected fibers by arbitrarily selecting 10 or more fibers as described later. The glass fiber is not limited to a single fiber diameter, but may be a mixture of a plurality of fiber diameters (for example, 1 μm and 10 μm).

The above-mentioned non-woven fabric may contain a fiber material insoluble in the electrolytic solution, in addition to the glass fiber. As the fiber material other than glass fiber, polymer fiber (polyolefin fiber, acrylic fiber, polyester fiber such as polyethylene terephthalate fiber, etc.), pulp fiber and the like can be used. The separator is preferably formed of fibrous material, for example, 60% by mass or more. The proportion of glass fibers in the fiber material forming the separator is preferably 60% by mass or more. Further, the non-woven fabric may contain an inorganic powder other than silica particles (for example, glass powder, diatomaceous earth) and the like.

The ratio of silica particles having an average particle diameter of 1 to 10 μm in the separator is, for example, 1 to 50% by mass, and from the viewpoint of easily reducing the internal resistance, 1 to 30% by mass is preferable, From the viewpoint of easily suppressing elution, 10 to 30 mass% is more preferable.

The separator may include the above-mentioned non-woven fabric, for example, may be composed only of the above-mentioned non-woven fabric, and if necessary, a laminate of the above-mentioned non-woven fabric and other non-woven fabric and/or microporous membrane or the like. Alternatively, it may be a product obtained by laminating different materials of the same type on the above-mentioned non-woven fabric, or a product obtained by engaging the above-mentioned non-woven fabric with materials of different types or the same type by male and female or the like. It is preferable to dispose the separator so that the non-woven fabric is in contact with at least the main surface of the negative electrode plate. Examples of other non-woven fabrics include non-woven fabrics of polymer fibers (polyolefin fibers, acrylic fibers, polyester fibers such as polyethylene terephthalate fibers), non-woven fabrics of pulp fibers, and glass fiber non-woven fabrics containing no silica particles having an average particle size of 1 to 10 μm. used. The microporous membrane is a porous sheet mainly composed of components other than fiber components. For example, a composition containing a pore-forming agent (such as polymer powder and/or oil) is extruded into a sheet and then the pore-forming agent is added. It is obtained by removing and forming pores. The material forming the separator is preferably acid resistant, and the polymer component is preferably polyolefin such as polyethylene or polypropylene.

The thickness (total thickness) of the separator may be selected according to the size of the lead storage battery, the distance between the electrode plates, and the like, but is, for example, 0.5 to 5 mm.

(Electrolyte)
The electrolytic solution is an aqueous solution containing sulfuric acid. The specific gravity at 20° C. of the electrolytic solution in the lead storage battery in a fully charged state after formation is, for example, 1.10 to 1.35 g/cm ³ , and preferably 1.20 to 1.35 g/cm ³ .

Next, a method of analyzing each physical property will be described.
(1) Density of Negative Electrode Material The density of the negative electrode material means the value of the bulk density of the fully charged negative electrode material after chemical formation, and is measured as follows. The battery after chemical formation is fully charged, disassembled, and the obtained negative electrode plate is washed with water and dried to remove the electrolytic solution in the negative electrode plate. Then, the negative electrode material is separated from the negative plate to obtain an unground measurement sample. After charging the sample into the measuring container and evacuating it, filling the mercury with a pressure of 0.5 to 0.55 psia, measuring the bulk volume of the negative electrode material, and dividing the mass of the measurement sample by the bulk volume. The bulk density of the negative electrode material is determined. The volume obtained by subtracting the volume of mercury injected from the volume of the measurement container is the bulk volume.

In the present specification, the fully charged state of the lead storage battery means that the lead storage battery after formation is subjected to constant current constant voltage charging of 2.23 V/cell at a rate of 5 hours in a gas tank at 25° C. and constant voltage charging. The charging is completed when the charging current at that time becomes 1 mCA or less.
In the present specification, 1 CA is a current value for discharging the nominal capacity of the battery in 1 hour. For example, if the battery has a nominal capacity of 30 Ah, 1 CA is 30 A and 1 mCA is 30 mA.

(2) Analysis of organic shrink proofing agent First, a lead storage battery in a fully charged state after chemical formation is disassembled, a negative electrode plate is taken out, washed with water to remove sulfuric acid, and dried. Next, a negative electrode material (initial sample) is collected from the dried negative electrode plate, and the initial sample is analyzed by the following method.

(2-1) Qualitative Analysis of Organic Strain Relief Agent in Negative Electrode Material An initial sample is immersed in a 1 mol/L sodium hydroxide (NaOH) aqueous solution to extract the organic shrink proof agent. Next, insoluble components are removed by filtration from the extracted aqueous NaOH solution containing an organic shrinkage inhibitor, and the obtained filtrate is desalted by dialysis, concentrated, and dried. Desalting may be carried out by passing the filtrate through an ion exchange membrane, or by putting the filtrate in a dialysis tube and immersing it in distilled water. This gives a powder sample of the organic shrink proofing agent.

Infrared spectroscopic spectrum measured using a powder sample of the organic anti-shrinking agent thus obtained and UV-visible absorption spectrum measured with an ultraviolet-visible spectrophotometer by dissolving the powder sample with distilled water etc., with a predetermined solvent such as heavy water The organic shrinkage inhibitor species are identified using a combination of information obtained from the dissolution and NMR spectra of the resulting solution.

(2-2) Content of Organic Strain Reducing Agent in Negative Electrode Material In the same manner as in (2-1) above, after obtaining a filtrate of a NaOH aqueous solution containing an organic restraining agent, the ultraviolet-visible absorption spectrum of the filtrate is measured. The content of the organic anti-shrinking agent in the negative electrode material can be quantified using the spectral intensity and the calibration curve prepared in advance.

When a lead-acid battery with an unknown content of organic anti-shrink agent is obtained and the content of the organic anti-shrink agent is measured, it is not possible to exactly specify the structural formula of the organic anti-shrink agent, so the same organic Agents may not be used. In this case, the organic shrinkage agent extracted from the negative electrode of the battery is calibrated using a separately available organic shrinkage agent showing a similar shape in the ultraviolet-visible absorption spectrum, infrared spectrum, and NMR spectrum. By creating a line, the content of the organic anti-shrinking agent can be measured using the UV-visible absorption spectrum.

(2-3) Content of elemental sulfur in organic strain suppressor As in (2-1) above, after obtaining a powder sample of the organic strain suppressor, the content of 0.1 g of the organic strain suppressor was measured by the oxygen combustion flask method. The elemental sulfur is converted to sulfuric acid. At this time, by burning the powder sample in the flask containing the adsorbent, an eluate in which sulfate ions are dissolved in the adsorbent is obtained. Next, the eluate is titrated with barium perchlorate using thorin as an indicator to determine the content (C1) of the elemental sulfur in 0.1 g of the organic shrink proofing agent. Next, C1 is multiplied by 10 to calculate the content (μmol/g) of the elemental sulfur in the organic shrink-proofing agent per 1 g.

(3) Analysis of glass fiber and silica particles The existing fully charged lead acid battery is disassembled, the separator is taken out, the sulfuric acid is removed by washing with water, and then dried. Next, the dried separator is crushed, and the crushed sample is analyzed by the following method.

(3-1) Average Fiber Diameter of Glass Fiber A crushed sample is observed with an optical microscope or an electron microscope, 10 or more fibers whose length can be measured are selected, and an enlarged photograph thereof is taken. Next, the image of each fiber is image-processed to determine the fiber diameter near the center in the length direction of the fiber. The average of the obtained fiber diameters may be calculated and used as the average fiber diameter of the glass fibers.

(3-2) Content of Glass Fiber in Separator The mass ratio C (%) of glass fiber in the separator can be determined when the glass fiber can be isolated from the ground sample. At this time, the mass ratio C(%) is obtained from C(%)=100x by using the mass x(g) of the glass fiber isolated from the crushed sample of 1 g, for example.

The volume ratio Cv of glass fibers in the separator can be determined even when it is difficult to isolate the glass fibers from the ground sample. First, arbitrary cross-sectional photographs of a crushed sample are taken at a plurality of locations, the cross-sectional photographs are subjected to image processing, and the glass fibers included in a rectangular region having a length (L ₁ ) 10 times the average fiber length as one side are included. Find the area s ₁ . At this time, the ratio of s ₁ occupying the area (L ₁ ² ) of the rectangular region can be regarded as the volume ratio Cv of the glass fiber in the separator. Volume ratio Cv is calculated from _{Cv (%) = 100s 1 /} L 1 2.

(3-3) Average particle diameter of silica particles First, the fibers of the glass separator are loosened by hand, and the silica particles separated from the fibers at that time are observed with an optical microscope or an electron microscope to measure the particle diameter. Select 10 or more and take a magnified picture of them. Next, the photograph of each particle is image-processed to determine the particle diameter. The average of the obtained particle sizes may be calculated and used as the average particle size of the silica particles.

(3-4) Content of silica particles in the separator The mass ratio D (%) of the silica particles in the separator can be determined when the silica particles can be isolated from the ground sample. At this time, the mass ratio D(%) is obtained from D(%)=100y using, for example, the mass y(g) of the silica particles isolated from 1 g of the ground sample.

The volume ratio Dv of silica particles in the separator can be obtained even when it is difficult to isolate the silica particles from the ground sample. First, arbitrary cross-sectional photographs of a crushed sample are taken at a plurality of locations, the cross-sectional photographs are subjected to image processing, and the silica particles contained in a rectangular region having a length (L ₂ ) 10 times the average particle diameter as one side are included. The area s ₂ is calculated. At this time, the ratio of s ₂ to the area (L ₂ ² ) of the rectangular region can be regarded as the volume ratio Dv of the silica particles in the separator. The volume ratio Dv is calculated from Dv (%)=100s ₂ /L ₂ ² .

FIG. 1 is a perspective view schematically showing an example of a lead storage battery according to an embodiment of the present invention with a lid removed. 2A is a front view of the lead storage battery of FIG. 1, and FIG. 2B is a cross-sectional view taken along the line IIB-IIB of FIG. 2A.
The lead storage battery 1 includes a battery case 10 that contains an electrode plate group 11 and an electrolytic solution (not shown). The electrode plate group 11 is configured by laminating a plurality of negative electrode plates 2 and a plurality of positive electrode plates 3 with a separator 4 in between.

An ear portion (not shown) for collecting current is provided on an upper portion of each of the plurality of negative electrode plates 2 so as to project upward. Ears (not shown) for collecting current are provided on the upper portions of the plurality of positive electrode plates 3 so as to project upward. The ears of the negative electrode plate 2 are connected and integrated by the negative electrode strap 5a. Similarly, the ears of the positive electrode plate 3 are also connected and integrated by the positive electrode strap 5b. A negative pole 6a is fixed to the negative strap 5a, and a positive pole 6b is fixed to the positive strap 5b.

Hereinafter, the present invention will be described more specifically based on Examples and Comparative Examples, but the present invention is not limited to the following Examples.

<<Example 1>>
(1) Preparation of Negative Electrode Plate Lead powder, water, dilute sulfuric acid, barium sulfate, carbon black, and a predetermined amount of an organic shrink proofing agent were mixed to obtain a negative electrode paste. The negative electrode paste was filled in the mesh portion of the casting grid made of Pb-Ca-Sn alloy, aged and dried to obtain an unformed negative electrode plate.

The amount of the organic anti-shrinking agent is adjusted so that the content (A (mass %)) of the organic anti-shrinking agent is 0.15% by mass with respect to 100% by mass of the negative electrode material which has already been formed and is fully charged. And added to the negative electrode paste. Further, when the negative electrode paste was prepared, the amounts of water and dilute sulfuric acid added to the negative electrode paste were adjusted so that the density of the negative electrode material after fully charged in the existing formation was 2.5 g/cm ³ .

In addition, the density of the negative electrode material was obtained by using the measurement sample that was collected by fully charging the battery after formation and then disassembling it by the procedure described above. The battery was fully charged according to the procedure described above. The density of the negative electrode material was measured by the method described above using an automatic porosimeter (Autopore IV9505) manufactured by Shimadzu Corporation.

As the organic anti-shrink agent, a condensate of bisphenol compound introduced with sulfonic acid group with formaldehyde was used. Here, the amount of sulfonic acid groups to be introduced was controlled so that the content of elemental sulfur in the organic shrink-proofing agent was 4000 μmol/g.
Regarding the sulfur element content (μmol/g) in the organic anti-shrink agent, there should be no difference between the values measured before the negative electrode material was prepared and when the lead storage battery was disassembled and the organic anti-shrink agent was extracted. It was confirmed. Therefore, as the sulfur element content in the organic shrink-proofing agents described in Examples and Comparative Examples, the value obtained for the organic shrink-proofing agent before preparing the negative electrode material is described below.

(2) Preparation of positive electrode plate Lead powder, water, and sulfuric acid were kneaded to prepare a positive electrode paste. The positive electrode paste was filled in the mesh portion of the casting grid made of Pb-Ca-Sn alloy, aged and dried to obtain an unformed positive electrode plate.

(3) Manufacture of Lead Acid Battery Using four unformed negative electrode plates and three unformed positive electrode plates, a separator is interposed between the negative electrode plate and the positive electrode plate, and the negative electrode plates and the positive electrode plates are alternately laminated. Thereby, the electrode plate group was formed. As the separator, a non-woven fabric obtained by mixing glass fibers and silica particles (average particle diameter 3 μm) by wet papermaking was used.

The mass ratio C of the glass fibers and the mass ratio D of the silica particles in the separator were 80% by mass and 20% by mass, respectively. When the glass fibers and the silica particles in the separator were observed with an electron microscope, the average fiber diameter of the glass fibers was 0.7 μm, and the average particle diameter of the silica particles was 3 μm.

The electrode plate group was housed in a polypropylene battery case, an electrolytic solution was injected, and formation was performed in the battery case to assemble a control valve type lead acid battery. The output of the lead acid battery is 2V, and the nominal capacity is 500 Ah (5-hour rate).

The content (A (mass %)) of the organic anti-shrinking agent contained in the negative electrode material (100 mass %) taken out from the negative electrode plate was determined for one manufactured lead acid battery by the procedure described above. The content of the organic shrink proofing agent thus quantified was slightly different from the content of the organic shrink proofing agent (B (mass %)) in the negative electrode material (100 mass %) prepared for the lead storage battery. It becomes a value. Therefore, the ratio R (=A/B) of these contents A and B is obtained in advance, and when the negative electrode material used for the negative electrode plate of another lead storage battery is prepared, the ratio R is used to The content (B (mass %)) of the organic shrink proofing agent in the prepared negative electrode material was adjusted so that the content (A (mass %)) of the organic shrink proofing agent in the material was a predetermined value. Further, in Examples and Comparative Examples, the ratio R is calculated for each sulfur element content of the organic shrink-proofing agent to be used. The content (B (mass %)) of the organic anti-shrink agent was adjusted.

<<Examples 2-6 and Comparative Examples 1-2>>
Content of elemental sulfur in the organic anti-shrink agent is 5000 μmol/g (Example 2), 6000 μmol/g (Example 3), 7000 μmol/g (Example 4), 8000 μmol/g (Example 5), 9000 μmol/g (Example 6), 2000 μmol/g (Comparative Example 1), or 3000 μmol/g (Comparative Example 2), the amount of sulfonic acid groups introduced into the condensate of the bisphenol compound with formaldehyde was adjusted. A negative electrode plate was formed in the same manner as in Example 1 except that the organic shrink-preventing agents having these sulfur element contents were used. A lead storage battery was assembled in the same manner as in Example 1 except that the obtained negative electrode plate was used.

<<Comparative example 3>>
As the organic anti-shrink agent, lignin derived from a natural product and having a sulfur element content of 600 μmol/g was used. A glass fiber non-woven fabric was used as the separator. A negative electrode plate was formed in the same manner as in Example 1 except these. A lead storage battery was assembled in the same manner as in Example 1 except that the obtained negative electrode plate was used.

<<Comparative Examples 4 to 10>>
Content of elemental sulfur in the organic anti-shrink agent is 2000 μmol/g (Comparative Example 4), 3000 μmol/g (Comparative Example 5), 4000 μmol/g (Comparative Example 6), 5000 μmol/g (Comparative Example 7), 6000 μmol/g (Comparative Example 8), 7000 μmol/g (Comparative Example 9), or 8000 μmol/g (Comparative Example 10), the amount of sulfonic acid groups introduced into the condensate of the bisphenol compound with formaldehyde was adjusted. Organic shrinkage inhibitors having the contents of these elemental sulfur were used respectively. As the separator, a non-woven fabric of glass fiber was used. A negative electrode plate was formed in the same manner as in Example 1 except for these.
A lead storage battery was assembled in the same manner as in Example 1 except that the obtained negative electrode plate was used.

<<Examples 7-12 and Comparative Examples 11-12>>
A negative electrode plate was produced in the same manner as in Example 1 except that the amounts of water and dilute sulfuric acid added to the negative electrode paste were adjusted so that the density of the already-formed negative electrode material was 3.5 g/cm ^3. Example 7).

Further, the amounts of water and diluted sulfuric acid added to the negative electrode paste were adjusted so that the negative electrode material had a density of 3.5 g/cm ³ . Furthermore, the content of the elemental sulfur in the organic anti-shrink agent was 5000 μmol/g (Example 8), 6000 μmol/g (Example 9), 7000 μmol/g (Example 10), 8000 μmol/g (Example 11), 9000 μmol /G (Example 12), 2000 μmol/g (Comparative Example 11), or 3000 μmol/g (Comparative Example 12), the amount of sulfonic acid groups introduced into the condensate of the bisphenol compound with formaldehyde is adjusted. did. A negative electrode plate was formed in the same manner as in Example 1 except for these.
Then, a lead storage battery was assembled in the same manner as in Example 1 except that the negative electrode plate obtained above was used.

<<Comparative Example 13>>
Lignin was used as an organic shrinkage agent in the same manner as in Comparative Example 3 except that the amounts of water and dilute sulfuric acid added to the negative electrode paste were adjusted so that the density of the already formed negative electrode material was 3.5 g/cm ^3. To prepare a negative electrode plate. A lead storage battery was assembled in the same manner as in Comparative Example 3 except that the obtained negative electrode plate was used.

<<Comparative Examples 14 to 20>>
The amounts of water and dilute sulfuric acid added to the negative electrode paste were adjusted so that the density of the already formed negative electrode material was 3.5 g/cm ³ . Content of elemental sulfur in the organic anti-shrink agent is 2000 μmol/g (Comparative Example 14), 3000 μmol/g (Comparative Example 15), 4000 μmol/g (Comparative Example 16), 5000 μmol/g (Comparative Example 17), 6000 μmol/g (Comparative Example 18), 7000 μmol/g (Comparative Example 19), or 8000 μmol/g (Comparative Example 20), the amount of sulfonic acid groups introduced into the condensate of the bisphenol compound with formaldehyde was adjusted. A negative electrode plate was produced in the same manner as in Comparative Examples 4 to 10 except for these. A lead storage battery was assembled in the same manner as in Comparative Example 4 except that the obtained negative electrode plate was used.

<<Examples 13 to 17>>
A negative electrode plate was prepared in the same manner as in Example 1 except that the amounts of water and dilute sulfuric acid added to the negative electrode paste were adjusted so that the density of the already formed negative electrode material was 3.0 g/cm ^3. Example 13).
Further, the amounts of water and dilute sulfuric acid added to the negative electrode paste were adjusted so that the density of the negative electrode material was 3.0 g/cm ³ . The content of elemental sulfur in the organic anti-shrink agent should be 5000 μmol/g (Example 14), 6000 μmol/g (Example 15), 7000 μmol/g (Example 16), or 8000 μmol/g (Example 17). In each case, the amount of sulfonic acid groups introduced into the condensate of the bisphenol compound with formaldehyde was adjusted. A negative electrode plate was formed in the same manner as in Example 1 except for these.
Then, a lead storage battery was assembled in the same manner as in Example 1 except that the negative electrode plate obtained above was used.

<<Examples 18 to 22>>
A negative electrode plate was prepared in the same manner as in Example 1 except that the amounts of water and dilute sulfuric acid added to the negative electrode paste were adjusted so that the density of the already formed negative electrode material was 4.0 g/cm ^3. Example 18).
Further, the amounts of water and dilute sulfuric acid added to the negative electrode paste were adjusted so that the density of the negative electrode material was 4.0 g/cm ³ . The content of elemental sulfur in the organic anti-shrink agent should be 5000 μmol/g (Example 19), 6000 μmol/g (Example 20), 7000 μmol/g (Example 21), or 8000 μmol/g (Example 22). In each case, the amount of sulfonic acid groups introduced into the condensate of the bisphenol compound with formaldehyde was adjusted. A negative electrode plate was formed in the same manner as in Example 1 except for these.
Then, a lead storage battery was assembled in the same manner as in Example 1 except that the negative electrode plate obtained above was used.

<<Examples 23 to 27>>
A negative electrode plate was produced in the same manner as in Example 1 except that the amounts of water and dilute sulfuric acid added to the negative electrode paste were adjusted so that the density of the already-formed negative electrode material was 4.5 g/cm ^3. Example 23).
Further, the amounts of water and dilute sulfuric acid added to the negative electrode paste were adjusted so that the density of the negative electrode material was 4.5 g/cm ³ . The content of elemental sulfur in the organic anti-shrink agent should be 5000 μmol/g (Example 24), 6000 μmol/g (Example 25), 7000 μmol/g (Example 26), or 8000 μmol/g (Example 27). In each case, the amount of sulfonic acid groups introduced into the condensate of the bisphenol compound with formaldehyde was adjusted. A negative electrode plate was formed in the same manner as in Example 1 except for these.
Then, a lead storage battery was assembled in the same manner as in Example 1 except that the negative electrode plate obtained above was used.

<<Examples 28 to 29 and Comparative Examples 21 to 23>>
The amounts of water and dilute sulfuric acid added to the negative electrode paste were adjusted so that the density of the negative electrode material was 3.5 g/cm ³ . The amount of sulfonic acid groups introduced into the condensate of the bisphenol compound with formaldehyde was adjusted so that the content of elemental sulfur in the organic anti-shrink agent was 7,000 μmol/g. The average particle diameter of the silica particles contained in the separator is 0.01 μm (Comparative Example 21), 0.1 μm (Comparative Example 22), 1 μm (Example 28), 10 μm (Example 29) or 100 μm (Comparative Example 23). changed. A negative electrode plate was produced in the same manner as in Example 1 except for the above, and a lead acid battery was assembled in the same manner as in Example 1 except that the negative electrode plate obtained above was used.

[Evaluation 1]
With respect to the lead-acid batteries manufactured in Examples and Comparative Examples, a charge/discharge cycle test was performed at 25° C. at a discharge depth of 70%, and a cycle when the discharge end voltage at a depth of 70% discharge was less than 1.7V was performed. The number was calculated and the life cycle of the lead storage battery was evaluated.
In the charge/discharge cycle test, during discharge, the battery was discharged at a current value of 0.2 CA for 3.5 hours, and at the time of charging, a constant voltage of 2.42 V and a maximum current of 0.2 CA, and the amount of electricity charged was the amount of electricity discharged. The battery was charged with a constant voltage so as to be 102%. Then, uniform charging was performed every 6 cycles. In the uniform charging, in addition to normal charging, charging was performed for 8 hours at a voltage of 2.42V.

FIG. 3 shows the relationship between the content of sulfur element in the organic shrink proof agent and the life cycle of the lead storage battery in the case where the separator contains silica particles and the case where the separator does not contain silica particles in the above Examples and Comparative Examples. Note that FIG. 3 shows data when the density of the negative electrode material is 2.5 g/cm ³ and 3.5 g/cm ³ . In the comparative example using lignin, the life cycle is low. When the content of elemental sulfur is 3000 μmol/g, there is almost no difference in the life cycle number depending on whether or not silica particles are contained in the separator. When the content of elemental sulfur is 2000 μmol/g, a higher life cycle is obtained when the sulfur particles are not contained than when they are contained in the separator. On the other hand, when the content of elemental sulfur exceeds 3000 μmol/g, the life cycle is greatly improved when the sulfur particles are contained in the separator as compared with the case where the silica particles are not contained.

From FIG. 3, in the comparative example using the separator not containing silica particles, the life cycle becomes maximum when the content of the elemental sulfur is 4000 μmol/g or 5000 μmol/g, and even when the sulfur content is further increased, the life cycle is increased. Will fall. When the content of elemental sulfur is 8000 μmol/g, the life cycle is as low as that of lignin. On the other hand, in the examples using the separator containing silica particles, the sulfur element content exceeds 3000 μmol/g and is 9000 μmol/g or less, and a long life cycle is obtained. When the content of elemental sulfur is 4000 to 9000 μmol/g or 5000 to 9000 μmol/g, the life cycle is particularly high.

Table 1 shows the results of the life cycle when the content of the elemental sulfur was 4000 to 8000 μmol/g at each density of the negative electrode material.

As shown in Table 1, even when the density of the negative electrode material was 3 g/cm ³ , 4 g/cm ³ , and 4.5 g/cm ³ , a high life cycle was obtained as in the example shown in FIG. Was given. The life cycle increases as the density of the negative electrode material increases.

Regarding the lead storage batteries of Examples 28 to 29 and Comparative Examples 21 to 23, the relationship between the average particle size of silica particles and the life cycle was examined. FIG. 4 is a graph showing the relationship between the average particle size of silica particles in the separator and the life cycle of the lead storage battery. As shown in FIG. 4, when the average particle diameter of the silica particles is 1 to 10 μm, a high life cycle of 5000 cycles or more is ensured as compared with the case where the average particle diameter is smaller than 1 μm and larger than 10 μm. You can do it.

[Evaluation 2]
With respect to the manufactured lead storage battery, the amount of the organic shrinkproofing agent eluted from the negative electrode plate was measured. Here, the negative electrode plate was taken out from the lead-acid battery at the time of 200 cycles of the heavy load life test, the content C1 of the organic shrink proof agent in the negative electrode material was measured, and the organic shrink proof agent content C2 was compared with the initial content of the organic shrink proof agent. The elution amount of the shrinkproofing agent was calculated by the following formula.
Elution amount (%)={1-(C1/C2)}×100

FIG. 5 shows the relationship between the content of elemental sulfur in the organic anti-shrink agent and the elution amount of the organic anti-shrink agent. FIG. 5 shows the elution amount of the organic shrink proofing agent when the density of the negative electrode material was 2.5 g/cm ³ and 3.5 g/cm ³ , respectively, in the case where the separator contained silica particles and when the separator did not contain silica particles. It was From FIG. 5, when the content of the elemental sulfur exceeds 3000 μmol/g, the elution amount of the organic shrinkage preventive agent is greater in the case of using the separator containing silica particles than in the case of using the separator containing no silica particles. Is significantly reduced.

[Evaluation 3]
With respect to the lead-acid batteries manufactured in Examples and Comparative Examples, a charge/discharge cycle test was performed, and when charging at the 2000th cycle was completed, the specific resistance was measured as follows.
First, the negative electrode plate was taken out from the lead acid battery, washed with water, and dried. Two current lines and two voltage lines were connected at the center positions of the upper end and the lower end of the region of the negative electrode plate where the negative electrode material was present, and a direct current was passed by the four-terminal method to measure the drop voltage. Then, the specific resistance was calculated from the calibration curve showing the relationship between the voltage drop and the specific resistance obtained by the CAE analysis.

The specific resistance of the negative electrode material in each lead acid battery is a ratio (%) when the density of the negative electrode material is 3.5 g/cm ³ and the value in the lead acid battery of Comparative Example 13 using lignin is 100. expressed. In addition, the amount of lead sulfate accumulated was expressed as a mass ratio (%) when the total mass of the negative electrode material was 100.

In addition, at the 2000th cycle, the amount of lead sulfate accumulated in the lower portion of the negative electrode plate (at a position of 20% from the bottom of the height of the negative electrode plate) was examined. The amount of lead sulfate accumulated was determined as follows. First, the negative electrode material taken from the negative electrode plate was washed with water, dried and crushed. The amount of elemental sulfur contained in the pulverized product was measured using an elemental sulfur analyzer. Then, the content of elemental sulfur in lead sulfate was determined according to the following formula.

Elemental sulfur content in lead sulfate = (mass of elemental sulfur obtained by elemental sulfur analyzer)-(mass of sample x content of organic shrinkage agent x content of elemental sulfur in organic shrinkage agent)
Then, the amount of elemental sulfur contained in the obtained lead sulfate was converted into the amount of lead sulfate, and the lead sulfate concentration per unit mass of the sample was determined and used as the lead sulfate accumulation amount.

FIG. 6 shows the relationship between the content of sulfur element in the organic anti-shrink agent and the specific resistance of the negative electrode material. FIG. 7 shows the relationship between the content of elemental sulfur in the organic anti-shrink agent and the amount of lead sulfate accumulated in the lower region of the negative electrode plate. 6 and 7 show data when the density of the negative electrode material is 2.5 g/cm ³ and 3.5 g/cm ³ . Generally, when the density of the negative electrode material is low, the specific resistance is high and the lead sulfate accumulation amount is high. However, as shown in FIGS. 6 and 7, when the content of the elemental sulfur increased, the specific resistance and the density of the negative electrode material were 2.5 g/cm ³ and 3.5 g/cm ³ , respectively. The difference in lead sulfate accumulation is small. From these results, it can be said that the effect of the high sulfur element content becomes remarkable when the density of the negative electrode material is low. Further, from the viewpoint of suppressing the specific resistance to be small, it is advantageous to use an organic shrinkage inhibitor having a high sulfur element content, but when such an organic shrinkage inhibitor is used, softening and falling of the positive electrode are likely to be remarkable. Therefore, by using silica particles having an average particle diameter of 1 to 10 μm, it is possible to suppress softening and dropping of the positive electrode and to use an organic anti-shrink agent having a high sulfur element content, so that the specific resistance can be reduced.

The embodiment of the present invention is applicable to a control valve type lead storage battery, and is preferably used as a power source for an industrial power storage device such as an electric vehicle (forklift, etc.). It can also be used as a power source for a power storage device such as an automobile or a motorcycle.

1: Lead acid battery 2: Negative electrode plate 3: Positive electrode plate 4: Separator 5a: Negative strap 5b: Positive electrode strap 6a: Negative pole 6b: Positive pole 10: Battery case 11: Pole group

Claims (4)

A negative electrode plate, a positive electrode plate, a separator interposed between the negative electrode plate and the positive electrode plate, and an electrolytic solution,
The negative electrode plate includes a negative electrode current collector and a negative electrode material,
The negative electrode material contains an organic shrinkage inhibitor containing elemental sulfur,
The content of the elemental sulfur in the organic anti-shrink agent is more than 3000 μmol/g and not more than 9000 μmol/g,
The separator includes a non-woven fabric containing glass fibers and silica particles attached to the glass fibers,
The lead storage battery, wherein the silica particles have an average particle diameter of 1 to 10 μm. The lead acid battery according to claim 1, wherein the content of the elemental sulfur in the organic anti-shrink agent is 4000 to 9000 μmol/g. The lead acid battery according to claim 1 or 2, wherein the content of the sulfur element in the organic anti-shrink agent is 5000 to 9000 µmol/g. The lead acid battery according to any one of claims 1 to ³ , wherein the negative electrode material has a density of 2.5 to 4.5 g/cm ³ .

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