JP7180591B2 - lead acid battery - Google Patents

Description

The present invention relates to lead-acid batteries.

Lead-acid batteries are used in a variety of applications, including in-vehicle use and industrial use. A lead-acid battery includes a negative plate, a positive plate, and an electrolyte. The negative plate includes a current collector and a negative electrode material. Negative electrode materials include carbon materials, barium sulfate, and the like. Patent Document 1 proposes a negative electrode material containing graphite or carbon fiber, carbon black, barium sulfate, and having a density of 3.6 to 4.0 g/cm ³ . Patent Document 2 proposes a negative electrode material containing less than 0.6 mass% barium sulfate and having a density higher than 3.6 g/cm ³ . Patent Document 2 describes that the carbon content of the negative electrode material is 0.2 mass % or less, and that acetylene black is used as the carbon.

JP 2016-152131 A JP 2016-189260 A

In general, increasing the density of the negative electrode material improves cycle life. However, when carbon black is added to the negative electrode material to form a negative electrode plate having a high density of the negative electrode material, the coatability to the current collector deteriorates. In addition, depending on the composition of the negative electrode material, it may become difficult to charge the battery after deep discharge, and the cycle life may be shortened.

An object of the present invention is to facilitate the production of a negative electrode plate and to improve the cycle life performance of a lead-acid battery when performing deep discharge.

One aspect of the present invention is a lead-acid battery,
The lead-acid battery includes a negative plate and a positive plate,
The negative electrode plate includes a negative electrode material containing a carbon material and barium sulfate,
The carbon material includes a first carbon material having a particle size of 32 μm or more and a second carbon material having a particle size of less than 32 μm,
The ratio of the powder resistance R2 of the second carbon material to the powder resistance R1 of the first carbon material: R2/R1 is more than 15 and less than 230,
The content of barium sulfate in the negative electrode material is 0.2% by mass or more and 0.7% by mass or less,
The negative electrode material has a density of 3.8 g/cm ³ or more, and relates to the lead-acid battery.

According to the above aspects of the present invention, the negative electrode plate can be easily produced, and high cycle life performance of lead-acid batteries can be obtained even when performing deep discharge.

1 is a perspective view schematically showing a state in which a lid of a lead-acid battery according to one aspect of the present invention is removed; FIG. FIG. 2 is a front view of the lead-acid battery of FIG. 1; FIG. 2B is a cross-sectional view of the lead-acid battery of FIG. 2A taken along line IIB-IIB. 4 is a graph showing the relationship between the cycle life performance evaluated for lead-acid batteries A1 to A8 and B1 to B8 and the density of the negative electrode material. 4 is a graph showing the relationship between the cycle life performance evaluated for lead-acid batteries A3, A11 to A16, B3, and B11 to B16 and the content of barium sulfate in the negative electrode material.

A lead-acid battery according to one aspect of the present invention includes a negative plate and a positive plate. The negative plate includes a negative electrode material containing a carbon material and barium sulfate. The carbon material includes a first carbon material having a particle size of 32 μm or more and a second carbon material having a particle size of less than 32 μm. The ratio of the powder resistance R2 of the second carbon material to the powder resistance R1 of the first carbon material: R2/R1 is more than 15 and less than 230. The content of barium sulfate in the negative electrode material is 0.2% by mass or more and 0.7% by mass or less, and the density of the negative electrode material is 3.8 g/cm ³ or more.

In general, in the negative electrode plate of a lead-acid battery, increasing the density of the negative electrode material increases the conductivity of the negative electrode material and shortens the distance between the negative electrode active materials contained in the negative electrode material, resulting in Pb ²⁺ It is known that the diffusion speed of ions increases and the charging reaction speed improves. Therefore, it is believed that when the density of the negative electrode material is high, the accumulation of lead sulfate in the negative electrode plate is suppressed and the cycle life performance is improved.

On the other hand, conventionally, carbon black is added to the negative electrode material from the viewpoint of enhancing conductivity. A negative electrode plate is produced using a paste containing a negative electrode material, and a large amount of carbon black adsorbs a solvent contained in this paste. As a result, conventional pastes containing carbon black are greatly reduced in fluidity and spreadability, resulting in extremely poor applicability of the paste to the current collector. In addition, in general, from the viewpoint of uniformly applying the negative electrode material to the current collector, application using a machine such as a paste application dedicated filling machine (paster) is adopted. However, when the density of the negative electrode material is increased, the solid content of the paste increases, resulting in particularly poor paste applicability. For example, when carbon black is added alone to the negative electrode material so that the carbon black content in the negative electrode material is 0.6% by mass, the upper limit density that can be applied by machine is about 3.6 g / cm. ³ . Therefore, when carbon black is used alone, when the density of the negative electrode material exceeds 3.6 g/cm ³ and the density of the negative electrode material is high, mechanical coating is more difficult than before. If it is difficult to apply the paste by machine, it is difficult to manufacture the negative plate industrially.

The inventors have found that when the density of the negative electrode material is 3.6 g/cm ³ or less, the first carbon material or the second carbon material may be used alone, or both carbon materials may be used in combination. , we noticed that the cycle life performance did not change much. In general, the higher the density of the negative electrode material, the higher the cycle life performance and the charge acceptance performance, and the lower the capacity is suppressed even during charge-discharge cycles including deep discharge. However, as a result of investigation by the present inventor, it was found that when the first carbon material is used alone, even if the density of the negative electrode material is increased, the effect of additionally improving the cycle life is not so much.

Carbon materials having various powder resistances are generally known. The powder resistivity of powder materials is known to vary depending on the shape of the particles, the particle size, the internal structure of the particles, and/or the crystallinity of the particles. According to conventional technical knowledge, the powder resistance of the carbon material has no direct relationship with the resistance of the negative plate of the lead-acid battery, and is not considered to affect the cycle life performance.

In addition, for the purpose of suppressing permeation short circuit and suppressing aggregation of lead sulfate accumulated on the negative electrode plate, conventionally, addition of barium sulfate to the negative electrode material of lead-acid batteries has been studied. However, since barium sulfate is a non-conductor, depending on the composition of the negative electrode material, even if the density of the negative electrode material is increased, it may not be possible to charge the battery when a charge/discharge cycle including deep discharge is performed. In this case also, the cycle life performance is degraded.

According to the above aspect of the present invention, when the density of the negative electrode material is as high as 3.8 g/cm ³ or more, the particle diameter is different and the powder resistance ratio R2/R1 is more than 15 and less than 230. Combining the material with the second carbon material. As a result, the spreadability of the paste containing the negative electrode material (hereinafter also referred to as negative electrode paste) is increased, and the coatability is improved. , the negative electrode paste can be mechanically applied, and the negative electrode plate is easy to manufacture. As described above, according to the aspect of the present invention, the negative electrode plate can be easily produced in spite of the high density of the negative electrode material. When the powder resistance ratio R2/R1 is within the above range, the coating properties of the negative electrode paste are improved. This is considered to be due to moderate suppression of solvent adsorption.

In this specification, the expression that the negative electrode paste has excellent coatability means that the negative electrode paste can be applied to the negative electrode current collector by a machine (specifically, a paster).

Further, according to the aspect of the present invention, by combining the first carbon material and the second carbon material, the first carbon material and the second carbon material are more uniformly filled in the layer of the high-density negative electrode material. can do. Therefore, many conductive networks are easily formed in the negative electrode material. Increasing the density of the negative electrode material forms a dense conductive network containing metallic lead particles and a charge reaction field, increases the charge reaction rate in the negative electrode material, and improves the cycle life performance.

Furthermore, by setting the content of barium sulfate in the negative electrode material to 0.2% by mass or more and 0.7% by mass or less, it is possible to repeatedly charge and discharge even when performing charge-discharge cycles involving deep discharge. can. Therefore, even when deep discharge is involved, deterioration of the cycle life performance of the lead-acid battery can be suppressed. From the viewpoint of further enhancing the effect of improving the cycle life performance, the content of barium sulfate in the negative electrode material is preferably 0.2% by mass or more and 0.6% by mass or less.

The density of the negative electrode material is preferably 4.1 g/cm ³ or more. Even when the density of the negative electrode material is high, a uniform layer of the negative electrode material is likely to be formed because the negative electrode plate has high coatability. Moreover, since many conductive networks are formed, the cycle life performance can be further improved.

In general, when the density of the negative electrode material is increased, the amount of dilute sulfuric acid used in preparing the paste is reduced and/or the concentration of sulfuric acid in the dilute sulfuric acid is decreased in order to maintain the spreadability of the paste. is being done. As a result, the amount of sulfate groups in the negative electrode material is reduced. A decrease in the amount of sulfate radicals generally increases the spreadability of the paste, while decreasing the amount of lead sulfate in the negative electrode material in the resulting negative plate. It is known that when such a negative electrode plate (unformed negative electrode plate) is stored in the atmosphere, there is a problem that the content of lead carbonate in the negative electrode material increases. It has been found that when the content of lead carbonate in the negative electrode material is high, shedding of the negative electrode material and/or a decrease in the initial capacity of the negative plate can occur. For example, when an unformed negative plate containing approximately 20% by mass or more of lead carbonate in the negative electrode material is formed, the negative electrode material may fall off and/or the initial capacity of the negative plate may decrease. That is, the storage performance of the unformed negative electrode plate is degraded. From the viewpoint of suppressing deterioration in storage performance of unformed negative electrode plates, there is a method conventionally adopted, for example, in which the negative electrode plate after the paste has been applied is brought into contact with dilute sulfuric acid so that the surface of the negative electrode plate is impregnated with sulfate radicals. There is a way to However, even if such a method is employed, it is not possible to supply a sufficient amount of sulfate radicals to maintain the preservation performance.

Also in the aspect of the present invention, if the density of the negative electrode material is too high, it may be difficult to obtain high storage performance. Therefore, from the viewpoint of ensuring high storage performance of the unformed negative electrode plate, the density of the negative electrode material is preferably less than 4.7 g/cm ³ .

When preparing the negative electrode paste, in order not to reduce the amount of sulfate radicals, it is preferable to add a carbon material that does not reduce the extensibility and storage performance of the negative electrode paste. As such a carbon material, the ratio of the specific surface area S2 of the second carbon material to the specific surface area S1 of the first carbon material: S2/S1 is 350 or less, and the first carbon material and the second carbon material are used. is preferred. The effects of the first carbon material and the second carbon material exhibiting such S2/S1 ratios are particularly noticeable when the density of the negative electrode material is less than 4.7 g/cm ³ . Moreover, when the specific surface area ratio S2/S1 is 350 or less, the applicability of the negative electrode paste is improved.

Hereinafter, lead-acid batteries according to embodiments of the present invention will be described for each major component, but the present invention is not limited to the following embodiments.
(negative plate)
A negative plate of a lead-acid battery includes a negative electrode material. A negative plate can usually be composed of a negative current collector (negative grid, etc.) and a negative electrode material. In addition, the negative electrode material is obtained by removing the negative electrode current collector from the negative electrode plate.
A member such as a mat or pasting paper may be attached to the negative electrode plate. When the negative electrode plate includes such a member (attachment member), the negative electrode material excludes the negative electrode current collector and the attachment member. However, the thickness of the electrode plate is the thickness including the mat. When a mat is attached to the separator, the thickness of the mat is included in the thickness of the separator.

The negative electrode material includes a negative electrode active material (lead or lead sulfate) that develops capacity through an oxidation-reduction reaction. The negative electrode active material in the charged state is spongy metallic lead, but the unformed negative electrode plate is usually produced using lead powder. Moreover, the negative electrode material includes a carbon material and barium sulfate. The negative electrode material may further contain an organic anti-shrinking agent, etc., and may contain other additives as necessary.

(carbon material)
The carbon material includes a first carbon material having a particle size of 32 μm or more and a second carbon material having a particle size of less than 32 μm. The first carbon material and the second carbon material are separated and distinguished by a procedure described later.

Examples of each carbon material include carbon black, graphite, hard carbon, and soft carbon. Examples of carbon black include acetylene black, furnace black, and lamp black. Graphite may be any carbon material having a graphite-type crystal structure, and may be either artificial graphite or natural graphite.

In addition, among the first carbon material, the intensity of the peak (D band) that appears in the range of 1300 cm ^-1 to 1350 cm ^-1 in the Raman spectrum and the peak (G band) that appears in the range of 1550 cm ^-1 to 1600 cm ^-1 A carbon material having a ratio I _D /I _G of 0 or more and 0.9 or less is called graphite.

The first carbon material and the second carbon material are used so that the ratio of the powder resistance R2 of the second carbon material to the powder resistance R1 of the first carbon material: R2/R1 is more than 15 and less than 230. The type, specific surface area, and/or aspect ratio of the carbon material used to prepare the material may be selected or adjusted. In addition to these factors, the particle size of the carbon material used may also be adjusted. By selecting or adjusting these elements, the powder resistance of each carbon material of the first carbon material and the second carbon material can be adjusted, and as a result, the powder resistance ratio R2/R1 can be adjusted. can.

As the first carbon material, for example, at least one selected from the group consisting of graphite, hard carbon, and soft carbon is preferable. In particular, the first carbon material preferably contains at least graphite. The second carbon material preferably contains at least carbon black. Using these carbon materials facilitates adjustment of the powder resistance ratio R2/R1.

The ratio of the powder resistance R2 of the second carbon material to the powder resistance R1 of the first carbon material (powder resistance ratio R2/R1) should be more than 15 and less than 230. When the powder resistance ratio is within such a range, it is possible to obtain high applicability of the negative electrode paste and improve the cycle life performance. From the viewpoint of obtaining higher cycle life performance, the powder resistance ratio R2/R1 is preferably 80 or more. From the same point of view, the powder resistance ratio R2/R1 is preferably 220 or less. From the viewpoint of ensuring high storage performance of the unformed negative electrode plate, the powder resistance ratio R2/R1 is preferably less than 160, more preferably 150 or less. These lower and upper limits can be combined arbitrarily. The powder resistance ratio R2/R1 is, for example, more than 15 and 220 or less (or less than 160 or 150 or less), or 80 or more and less than 230 (or 220 or less, less than 160, or 150 or less).

The ratio of the specific surface area S2 of the second carbon material to the specific surface area S1 of the first carbon material: S2/S1 is preferably 350 or less. When the specific surface area ratio S2/S1 is within such a range, the applicability of the negative electrode paste can be further improved even when the density of the negative electrode material is increased. Moreover, when the first carbon material and the second carbon material having an S2/S1 ratio of 350 or less are used, high storage performance of the unformed negative electrode plate can be ensured. Such an S2/S1 ratio has an effect on storage performance, particularly when the density of the negative electrode material is less than 4.7 g/cm ³ (preferably 4.6 g/cm ³ or less, more preferably 4.5 g/cm ³ or less). ).

The average aspect ratio of the first carbon material may be, for example, 1 or more and 200 or less, 1.5 or more and 100 or less, or 1.5 or more and 35 or less.

The total content of the first carbon material and the second carbon material in the negative electrode material is, for example, 0.1% by mass or more, preferably 0.2% by mass or more, and has the effect of improving cycle life performance. is preferably 0.3% by mass or more from the viewpoint of further increasing the The upper limit of the total content of the first carbon material and the second carbon material depends on the density of the negative electrode material, the type of each carbon material, etc., but can be, for example, 1.5% by mass or less.

Among the above carbon materials, the content of the first carbon material in the negative electrode material is, for example, 0.05% by mass or more, and from the viewpoint of high negative electrode paste applicability and high cycle life improvement effect, It is preferably 0.1% by mass or more or 0.2% by mass or more. The upper limit of the content of the first carbon material in the negative electrode material depends on the density of the negative electrode material, the type of carbon material, etc., but is, for example, 1.5% by mass or less. The total content with the carbon material may be adjusted so as to fall within the above range.

The content of the second carbon material in the negative electrode material is, for example, 0.03% by mass or more, and is preferably 0.1% by mass or more from the viewpoint of easy formation of a conductive network in the negative electrode material .2% by mass or more. The upper limit of the content of the second carbon material in the negative electrode material depends on the density of the negative electrode material, the type of the carbon material, etc., but is, for example, 1% by mass or less and 0.6% by mass or less. is preferred, and 0.4% by mass or less is more preferred. The content of the second carbon material may be adjusted so that the total content of the first carbon material and the second carbon material is within the above range. The content of the second carbon material is, for example, 0.03% by mass or more and 1% by mass or less (or 0.6% by mass or less or 0.4% by mass or less), 0.1% by mass or more and 1% by mass or less ( Alternatively, 0.6% by mass or less or 0.4% by mass or less), or 0.2% by mass or more and 1% by mass or less (or 0.6% by mass or less or 0.4% by mass or less) .

A method for determining physical properties of the carbon material or a method for analysis will be described below.
(A) Analysis of carbon material (A-1) Separation of carbon material Disassemble a chemically charged lead-acid battery, remove the negative electrode plate, wash with water to remove sulfuric acid, and dry in a vacuum (under pressure lower than atmospheric pressure). dry). Next, the negative electrode material is collected from the dried negative electrode plate and pulverized. 30 mL of an aqueous nitric acid solution with a concentration of 60% by mass is added to 5 g of the pulverized sample and heated at 70°C. Further, 10 g of disodium ethylenediaminetetraacetate, 30 mL of 28% by mass aqueous ammonia, and 100 mL of water are added to the mixture, and heating is continued to dissolve the soluble matter. The sample thus pretreated is collected by filtration. The collected sample is passed through a sieve with an opening of 500 μm to remove large-sized components such as reinforcing materials, and the components that pass through the sieve are collected as carbon materials.

Then, when the recovered carbon material is wet-sieved using a sieve with an opening of 32 μm, the material that does not pass through the mesh of the sieve and remains on the sieve is designated as the first carbon material. Let the material that passes through be the second carbon material. In other words, the particle size of each carbon material is based on the size of the opening of the sieve. For wet sieving, JIS Z8815:1994 can be referred to. Specifically, the carbon material is placed on a sieve with an opening of 32 μm, and is sieved by gently shaking the sieve for 5 minutes while sprinkling ion-exchanged water. The first carbon material remaining on the sieve is recovered from the sieve by pouring ion-exchanged water, and separated from the ion-exchanged water by filtration. The second carbon material that has passed through the sieve is collected by filtration using a nitrocellulose membrane filter (opening 0.1 μm). The recovered first carbon material and second carbon material are each dried at a temperature of 110° C. for 2 hours. As the sieve with an opening of 32 μm, one provided with a sieve with a nominal opening of 32 μm specified in JIS Z 8801-1:2006 is used.

The content of each carbon material in the negative electrode material is obtained by measuring the mass of each carbon material separated by the above procedure and calculating the ratio (% by mass) of this mass in 5 g of the pulverized sample. shall be requested.

In this specification, the fully charged state of a lead-acid battery means that, in the case of a liquid-type battery, constant-current charging is performed in a water tank at 25° C. at a current of 0.2 CA until the voltage reaches 2.5 V/cell. Further, constant current charging was performed at 0.2 CA for 2 hours. In the case of a valve-regulated battery, the fully charged state is defined as a constant current and constant voltage charge of 2.23 V/cell at 0.2 CA in an air tank at 25°C. is 1 mCA or less, charging is terminated.
In this specification, 1CA is the same current value (A) as the nominal capacity (Ah) of the battery. For example, for a battery with a nominal capacity of 30Ah, 1CA is 30A and 1mCA is 30mA.

(A-2) Powder resistance of carbon material The powder resistance R1 of the first carbon material and the powder resistance R2 of the second carbon material are the first carbon material and the second carbon material separated by the procedure in (A-1) above. For each of the two carbon materials, 0.5 g of the sample was put into a powder resistance measurement system (manufactured by Mitsubishi Chemical Analytic Tech, MCP-PD51 type), and under a pressure of 3.18 MPa, JIS K 7194: 1994. It is a value measured by a four-probe method using a compliant low resistance resistivity meter (Loresta-GX MCP-T700, manufactured by Mitsubishi Chemical Analytech Co., Ltd.).

(A-3) Specific Surface Area of Carbon Material The specific surface area S1 of the first carbon material and the specific surface area S2 of the second carbon material are the BET specific surface areas of the first carbon material and the second carbon material, respectively. The BET specific surface area is determined using the BET formula by the gas adsorption method using each of the first carbon material and the second carbon material separated by the procedure (A-1) above. Each carbon material is pretreated by heating at a temperature of 150° C. for 1 hour in flowing nitrogen. Using the pretreated carbon material, the BET specific surface area of each carbon material is obtained using the following apparatus under the following conditions.
Measuring device: TriStar 3000 manufactured by Micromeritics
Adsorption gas: Nitrogen gas with a purity of 99.99% or more Adsorption temperature: Liquid nitrogen boiling point temperature (77K)
Calculation method of BET specific surface area: conforms to 7.2 of JIS Z 8830:2013

(A-4) Average aspect ratio of the first carbon material The first carbon material separated by the procedure in (A-1) above is observed with an optical microscope or an electron microscope, and 10 or more arbitrary particles are selected. , take a magnified photograph of it. Next, the photograph of each particle is subjected to image processing to obtain the maximum diameter d1 of the particle and the maximum diameter d2 in the direction orthogonal to this maximum diameter d1, and the aspect ratio of each particle is obtained by dividing d1 by d2. Ask. The average aspect ratio is calculated by averaging the obtained aspect ratios.

(barium sulfate)
The content of barium sulfate contained in the negative electrode material may be 0.2% by mass or more and 0.7% by mass or less. When the content of barium sulfate is within this range, it does not interfere with the electronic conductivity between the metal lead particles, so even if deep discharge is performed, lead sulfate is easily reduced during charging. As a result, it is possible to prevent charging from becoming difficult during charge-discharge cycles involving deep discharge. Therefore, even in charge-discharge cycles involving deep discharge, charge-discharge can be repeatedly performed, and deterioration of cycle life performance is suppressed. From the viewpoint of further increasing the effect of improving the cycle life performance, the content is preferably 0.2% by mass or more and 0.6% by mass or less.

A method for determining the content of barium sulfate contained in the negative electrode material will be described below.
(B) Analysis of Barium Sulfate (B-1) About 5 g of sample is taken out from the pulverized sample taken out from the lead-acid battery in the same manner as in (A-1) above, and the mass m1 (g) is accurately weighed. The weighed sample is placed in 30 cm ³ of an aqueous solution of nitric acid having a concentration of 10% by mass, and dissolved by heating. After cooling the resulting mixture, deionized water is added until the volume reaches 100 cm ³ , allowed to stand for 30 minutes, and the supernatant is collected in another beaker. 20 g of ammonium acetate and 30 cm ³ of water are added to the remaining precipitate and dissolved by heating. The resulting solution is poured into the above supernatant, brought to a boil, heated in this state for 5 minutes, and then allowed to stand for 1 hour. The resulting mixture is filtered through a membrane filter with a known mass, and the filtrate is recovered. Thoroughly wash the components remaining on the membrane filter with water. The used membrane filter is dried at 110° C. for 2 hours, and the mass after drying is measured. The insoluble residue mass m2 is obtained by subtracting the initial mass of the membrane filter from the measured value. The dried membrane filter is placed in a porcelain crucible of known mass and pyrolyzed. Then, the crucible is cooled to room temperature in a desiccator, the mass is measured, and the initial mass of the crucible is subtracted from this mass to obtain the mass m3 of the ignition residue.

(B-2) The filtrate recovered in (B-1) above is placed in a volumetric flask, and deionized water is added until the volume reaches 250 cm ³ . The atomic absorbance of the resulting solution is measured by atomic absorption spectroscopy using an Air-C ₂ H ₂ flame, selecting the 553.6 nm spectral line. The atomic absorbance is measured using an atomic absorption spectrophotometer (AA7000F, manufactured by Shimadzu Corporation). Based on a calibration curve separately prepared using a Ba salt solution with a standard concentration, the concentration of barium element in the solution is obtained from the above atomic absorbance, and the mass m4 (mg) of barium element contained in the filtrate is calculated. Ask. Then, the content c1 (% by mass) of soluble barium sulfate contained in the negative electrode material is calculated by the following formula.
c1 = 100 x (M1/M2) x (m4/m1)
Here, M1 is the molecular weight of barium sulfate (BaSO ₄ ) and M2 is the atomic weight of barium (Ba). A value of M1/M2=1.699 is used.

(B-3) From the mass m3 of the ignition residue in (B-1) above, the insoluble barium sulfate content c2 (% by mass) contained in the negative electrode material is calculated by the following formula.
c2 = 100 x m3/m1
Then, by totaling c1 and c2, the barium sulfate content (% by mass) contained in the negative electrode material in the fully charged state after formation is obtained.

(Organic shrink-proofing agent)
The organic shrinkage agent contained in the negative electrode material is an organic polymer containing elemental sulfur, generally containing one or more, preferably a plurality of aromatic rings in the molecule, and containing elemental sulfur as a sulfur-containing group. there is Among the sulfur-containing groups, the stable forms sulfonic acid or sulfonyl groups are preferred. The sulfonic acid group may exist in an acid form or in a salt form such as Na salt.

As the organic shrink-proofing agent, for example, lignins or synthetic organic shrink-proofing agents may be used. Synthetic organic shrink-proofing agents may be condensates of aromatic compounds having sulfur-containing groups with formaldehyde. Examples of lignins include lignin, lignin derivatives such as ligninsulfonic acid or salts thereof (alkali metal salts such as sodium salts, etc.). The organic shrink-proofing agents may be used singly or in combination of two or more. For example, lignins and a formaldehyde condensate of an aromatic compound having a sulfur-containing group may be used in combination. Bisphenols, biphenyls, naphthalenes and the like are preferably used as aromatic compounds.

The content of the organic shrinkage inhibitor contained in the negative electrode material is, for example, 0.01% by mass or more and 1.0% by mass or less, preferably 0.02% by mass or more and 0.8% by mass or less.

A method for quantifying the organic pre-scaling agent contained in the negative electrode material will be described below. Prior to quantitative analysis, the chemically formed lead-acid battery is fully charged and then disassembled to obtain the negative electrode plate to be analyzed. The obtained negative electrode plate is washed with water and dried to remove the electrolyte in the negative electrode plate. Next, an uncrushed initial sample is obtained by separating the negative electrode material from the negative plate.

[Organic shrinkage agent]
An unground initial sample is ground, and the ground initial sample is immersed in a 1 mol/L NaOH aqueous solution to extract the organic shrinkage agent. An insoluble component is removed by filtration from the NaOH aqueous solution containing the extracted organic expander. After desalting the resulting filtrate (hereinafter also referred to as the target filtrate for analysis), it is concentrated and dried to obtain a powder of the organic shrink-proofing agent (hereinafter also referred to as the target powder for analysis). Desalting may be performed by placing the filtrate in a dialysis tube and immersing it in distilled water.

Infrared spectrum of the powder to be analyzed, UV-visible absorption spectrum of a solution obtained by dissolving the powder to be analyzed in distilled water, etc., NMR spectrum of a solution obtained by dissolving the powder to be analyzed in a solvent such as heavy water, substances The organic expander is identified by obtaining information from pyrolysis GC-MS or the like, which can obtain information on individual constituent compounds.

The UV-visible absorption spectrum of the filtrate to be analyzed is measured. Using the spectrum intensity and a pre-made calibration curve, the content of the organic preservative in the negative electrode material is quantified. If the structural formula of the organic prepressant to be analyzed cannot be strictly specified and the calibration curve for the same organic prepressant cannot be used, the UV-visible absorption spectrum, infrared spectroscopy spectrum, and A calibration curve is generated using available organic preservatives, such as NMR spectra.

(Negative Electrode Material Density)
The density of the negative electrode material should be 3.8 g/cm ³ or more, preferably 4.1 g/cm ³ or more. Even at such high densities, the present invention can provide high coatability and excellent cycle life performance. In addition, it is possible to obtain high storage performance of the unformed negative electrode plate. The density of the negative electrode material is, for example, 4.7 g/cm ³ or less. From the viewpoint of ensuring high storage performance of the unformed negative electrode plate, it is preferably less than 4.7 g/cm ³ , more preferably 4.6 g/cm ³ or less or 4.5 g/cm ³ or less. preferable. These lower and upper limits can be combined arbitrarily. The density of the negative electrode material is, for example, 3.8 g/cm ³ or more and 4.7 g/cm ³ or less (or less than 4.7 g/cm 3 , 4.6 g/cm ^{3 or} less, or 4.5 g/cm ³ or less). ), 4.1 g/cm ³ or more and 4.7 g/cm ³ or less (or less than 4.7 g/cm ³ , 4.6 g/cm ³ or less, or 4.5 g/cm ³ or less).

The density of the negative electrode material means the value of the bulk density of the negative electrode material in a fully charged state after chemical conversion, and is measured as follows. After the chemically formed battery is fully charged and then disassembled, the obtained negative electrode plate is washed with water and dried to remove the electrolyte in the negative electrode plate. Next, the negative electrode material is separated from the negative plate to obtain an unpulverized measurement sample. After putting the sample into the measurement container and evacuating, mercury was filled at a pressure of 0.5 psia or more and 0.55 psia or less (≈ 3.45 kPa or more and 3.79 kPa or less) to measure the bulk volume of the negative electrode material, The bulk density of the negative electrode material is obtained by dividing the mass of the measurement sample by the bulk volume. The volume obtained by subtracting the mercury injection volume from the volume of the measurement container is defined as the bulk volume. The density of the negative electrode material is measured using an automatic porosimeter (Autopore IV9505, manufactured by Shimadzu Corporation).

(others)
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. Processing methods include, for example, expanding processing and punching processing.

The lead alloy used for the negative electrode current collector may be any of Pb--Sb-based alloy, Pb--Ca-based alloy, and Pb--Ca--Sn-based alloy. These lead alloys may further contain at least one selected from the group consisting of Ba, Ag, Al, Bi, As, Se, Cu, etc., as an additive element. Among these, Pb--Sb alloys are preferred, and this alloy may further contain at least one selected from the group consisting of Ag, Al, As, Se, etc. as an additive element.

The negative electrode plate can be formed by filling a negative electrode current collector with a negative electrode paste, aging and drying to prepare an unformed negative plate, and then forming the unformed negative plate. The negative electrode paste is prepared by adding water and dilute sulfuric acid to lead powder, a carbon material, and, if necessary, an organic anti-shrinking agent and/or various additives, and kneading the mixture. When aging, it is preferable to age the unformed negative electrode plate at a temperature and humidity higher than room temperature.

The formation of the negative electrode plate can be performed by immersing the electrode plate group including the unformed negative electrode plate in an electrolytic solution containing sulfuric acid in the battery case of the lead-acid battery and then charging the electrode plate group. . Formation may also be performed before assembly of the lead-acid battery or the electrode plate group. Formation produces spongy metallic lead.

(Positive plate)
There are two types of positive electrode plates for lead-acid batteries: paste type and clad type.
The pasted positive plate comprises a positive current collector and a positive electrode material. A positive electrode material is held by a positive current collector. The positive electrode current collector may be formed in the same manner as the negative electrode current collector, and can be formed by casting lead or a lead alloy or processing a sheet obtained by rolling a lead or lead alloy slab.

A clad positive electrode plate consists of a plurality of porous tubes, a metal core inserted into each tube, a current collector connecting the metal cores, and a positive electrode material filled in the tube into which the metal core is inserted. and a linking member for connecting a plurality of tubes. A combination of the core metal and the current collector connecting the core metals is called a positive electrode current collector.

Examples of the lead alloy used for the positive electrode current collector include Pb--Ca based alloys, Pb--Sb based alloys and Pb--Ca--Sn based alloys. Among them, it is preferable to use a Pb--Sb alloy.

The positive electrode material includes a positive electrode active material (lead dioxide or lead sulfate) that develops capacity through an oxidation-reduction reaction. The positive electrode material may contain other additives as needed.

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

A clad positive electrode plate is formed by filling lead powder or slurry lead powder into a tube having a metal core inserted therein and connecting a plurality of tubes together.

The formed unformed positive electrode plate is further formed. Formation produces lead dioxide. Formation of the positive electrode plate may be performed before assembly of the lead-acid battery or the electrode plate group.

(separator)
A separator is usually placed between the negative plate and the positive plate. A nonwoven fabric, a microporous film, or the like is used for the separator. The thickness and the number of separators interposed between the negative electrode plate and the positive electrode plate may be selected according to the distance between the electrodes.
A non-woven fabric is a mat in which fibers are intertwined without being woven, and is mainly composed of fibers. For example, 60 mass % or more of the separator is made of fibers. As the fiber, glass fiber, polymer fiber (polyolefin fiber, acrylic fiber, polyester fiber such as polyethylene terephthalate fiber, etc.), pulp fiber, and the like can be used. Among them, glass fiber is preferable. The non-woven fabric may contain components other than fibers, such as acid-resistant inorganic powder and a polymer as a binder.

On the other hand, a microporous membrane is a porous sheet mainly composed of components other than fiber components. Obtained by removing the agent to form pores. The microporous membrane is preferably composed of an acid-resistant material, preferably mainly composed of a polymer component. Polyolefins such as polyethylene and polypropylene are preferable as the polymer component.

The separator may be composed of, for example, only a nonwoven fabric, or may be composed only of a microporous film. The separator may also be a laminate of a nonwoven fabric and a microporous membrane, a laminate of different or the same type of materials, or a combination of different or the same type of materials with interlocking unevenness.

(Electrolyte)
The electrolyte is an aqueous solution containing sulfuric acid, and the specific gravity of the electrolyte at 20° C. in a lead-acid battery in a fully charged state after formation is, for example, 1.10 g/cm ³ or more and 1.35 g/cm ³ or less. .10 g/cm ³ or more and 1.30 g/cm ³ or less, or 1.20 g/cm ³ or more and 1.30 g/cm ³ or less.

FIG. 1 is a perspective view schematically showing an example of a lead-acid battery according to an embodiment of the present invention with the lid removed. 2A is a front view of the lead-acid battery of FIG. 1, and FIG. 2B is a cross-sectional view taken along line IIB-IIB of FIG. 2A. A battery case 10 is provided. The electrode plate group 11 is configured by stacking a plurality of negative electrode plates 2 and positive electrode plates 3 with separators 4 interposed therebetween. Here, a state in which the negative electrode plate 2 is wrapped with the bag-shaped separator 4 is shown, but the shape of the separator is not particularly limited.

An upper portion of each of the plurality of negative electrode plates 2 is provided with a current-collecting ear (not shown) projecting upward. Each upper portion of the plurality of positive electrode plates 3 is also provided with a current collecting ear (not shown) protruding upward. The ears of the negative electrode plate 2 are connected to each other by a negative electrode strap 5a to be integrated. Similarly, the ears of the positive electrode plate 3 are also connected and integrated by the positive electrode strap 5b. A lower end portion of the negative electrode column 6a is fixed to the upper portion of the negative electrode strap 5a, and a lower end portion of the positive electrode column 6b is fixed to the upper portion of the positive electrode strap 5b.

A lead-acid battery according to one aspect of the present invention is collectively described below.
(1) One aspect of the present invention is a lead-acid battery,
The lead-acid battery includes a negative plate and a positive plate,
The negative electrode plate includes a negative electrode material containing a carbon material and barium sulfate,
The carbon material includes a first carbon material having a particle size of 32 μm or more and a second carbon material having a particle size of less than 32 μm,
The ratio of the powder resistance R2 of the second carbon material to the powder resistance R1 of the first carbon material: R2/R1 is more than 15 and less than 230,
The content of barium sulfate in the negative electrode material is 0.2% by mass or more and 0.7% by mass or less,
The lead-acid battery, wherein the negative electrode material has a density of 3.8 g/cm ³ or more.

(2) In (1) above, the ratio: R2/R1 is preferably 80 or more and less than 230.

(3) In (1) or (2) above, the ratio: R2/R1 is preferably 80 or more and 220 or less.

(4) In any one of (1) to (3) above, the negative electrode material preferably has a density of 4.1 g/cm ³ or more.

(5) In any one of (1) to (4) above, the negative electrode material preferably has a density of less than 4.7 g/cm ³ .

(6) In (5) above, the ratio of the specific surface area S2 of the second carbon material to the specific surface area S1 of the first carbon material: S2/S1 is preferably 350 or less.

(7) In any one of (1) to (6) above, the content of barium sulfate in the negative electrode material is preferably 0.2% by mass or more and 0.6% by mass or less.

(8) In any one of (1) to (7) above, the ratio R2/R1 is preferably 80 or more and less than 160.

(9) In any one of (1) to (8) above, the ratio R2/R1 is preferably 80 or more and 150 or less.

(10) In (6) above, the density of the negative electrode material is preferably 4.6 g/cm ³ or less or 4.5 g/cm ³ or less.

(11) In any one of (1) to (10) above, the content of the first carbon material in the negative electrode material is preferably 0.05% by mass or more.

(12) In any one of (1) to (11) above, the content of the first carbon material in the negative electrode material is, for example, 1.5% by mass or less.

(13) In any one of (1) to (12) above, the content of the second carbon material in the negative electrode material is preferably 0.1% by mass or more.

(14) In any one of (1) to (13) above, the content of the second carbon material in the negative electrode material is preferably 0.6% by mass or less.

(15) In any one of (1) to (14) above, it is preferable that the first carbon material contains at least graphite, and the second carbon material contains at least carbon black.

[Example]
EXAMPLES The present invention will be specifically described below based on examples and comparative examples, but the present invention is not limited to the following examples.

《Lead storage battery A1》
A lead-acid battery A1 for a forklift having a nominal capacity of 200 Ah and having three clad type electrode plates as the positive electrode plate and four paste type electrode plates as the negative electrode plate is prepared by the following procedure.

(1) Preparation of negative electrode plate The negative electrode plate is a plate-shaped grid-shaped negative electrode current collector (long side length 271 mm, short side length 142 mm, thickness 2.8 mm or more and 3.7 mm or less), and the negative electrode paste is applied. created by inserting At this time, the mass of the negative electrode material after chemical conversion was 465 ± 6 g per negative electrode plate, and the negative electrode current collector and the paste coating layer were adjusted so that the density of the negative electrode material was the design value shown in Table 1. Adjust thickness. The negative electrode paste is applied using a paste (manufactured by Winkel) so that there is no void in the grid of the current collector. However, if it is not possible to apply the negative electrode paste with a paste, it is applied manually using a trowel.

The negative electrode paste is prepared by mixing lead powder, water, dilute sulfuric acid, barium sulfate, a carbon material, and an organic shrink-proofing agent using a mixer (manufactured by Dalton).
Carbon black (Ketjenblack (registered trademark)) and graphite (flaky graphite, average particle diameter D ₅₀ : 110 μm) are used as the carbon material. Sodium ligninsulfonate is used as the organic anti-shrinking agent, and the amount added is adjusted so that the content contained in 100% by mass of the negative electrode material is 0.1% by mass, and then blended into the negative electrode paste. The content (design value) of barium sulfate contained in 100% by mass of the negative electrode material is 0.6% by mass. When preparing the negative electrode paste, the amounts of water and dilute sulfuric acid added to the negative electrode paste are adjusted so that the density of the negative electrode material that has been formed and is fully charged has the design value shown in Table 1. It should be noted that there is almost no difference between the density (measured value) of the negative electrode material obtained from the collected measurement sample and the design value by dismantling the fully charged battery in the above-described procedure.

(2) Fabrication of Positive Electrode Plate As the positive electrode plate, a clad electrode plate obtained by filling 14 tubes with an outer diameter of 10 mm with a positive electrode material is used. The amount of the positive electrode material to be applied is adjusted so that the mass of the positive electrode material after chemical conversion is 792±8 g per positive electrode plate.

(3) Assembly of lead-acid battery The obtained negative electrode plate and positive electrode plate are immersed in dilute sulfuric acid having a concentration of 7% by mass, and tank formation is performed in this state. An electrode plate assembly is produced by laminating the chemically formed negative electrode plate and positive electrode plate with a separator interposed therebetween. The resulting electrode plate group is placed in a battery case, and 2000 cm ³ of dilute sulfuric acid having a specific gravity of 1.28 at 20° C. is poured into the container to fabricate a lead-acid battery A1. Similarly, a total of four lead-acid batteries A1 are produced.

In this lead-acid battery, the content of the first carbon material contained in the negative electrode material is set to 0.4% by mass, and the content of the second carbon material is set to 0.2% by mass. Also, the powder resistance ratio R2/R1 is assumed to be 100. The ratio (=S2/S1) of the specific surface area S2 of the second carbon material to the specific surface area S1 of the first carbon material is 350. However, these values are obtained when the negative electrode plate of the manufactured lead-acid battery is taken out and the carbon material contained in the negative electrode material is separated into the first carbon material and the second carbon material by the procedure described above. It is a value obtained as the content of each carbon material contained in the electrode material (100% by mass). The powder resistances R1 and R2, the powder resistance ratio R2/R1, and the specific surface area ratio S2/S1 of each carbon material are also obtained from the manufactured lead-acid battery by the procedure described above.

《Lead-acid batteries A2 to A8》
The amounts of water and dilute sulfuric acid added to the negative electrode paste are adjusted so that the design value of the density of the negative electrode material that has already been chemically formed becomes the value shown in Table 1. Other than this, the lead-acid batteries A2 to A8 are assembled in the same manner as the lead-acid battery A1 except that the negative plate is produced in the same manner as the lead-acid battery A1, and the obtained negative electrode plate is used.

《Lead-acid batteries B1 to B8》
Only carbon black (Ketjenblack (registered trademark)) is used as the carbon material. In this lead-acid battery, the content of the second carbon material is set to 0.6% by mass. Other than these, the negative electrode plate is formed in the same manner as the lead-acid battery A1. A lead-acid battery B1 is assembled in the same manner as the lead-acid battery A1 except that the obtained negative electrode plate is used.

The amounts of water and dilute sulfuric acid added to the negative electrode paste are adjusted so that the design value of the density of the negative electrode material that has already been chemically formed becomes the value shown in Table 1. Other than this, lead-acid batteries B2 to B8 are assembled in the same manner as lead-acid battery B1 except that a negative plate is produced in the same manner as lead-acid battery B1 and the obtained negative electrode plate is used.

<<Lead-acid batteries D1 and D2>>
The amounts of water and dilute sulfuric acid added to the negative electrode paste are adjusted so that the carbon material is not used in the production of the negative electrode plate and the design value of the density of the negative electrode material already formed is the value shown in Table 1. Other than these, the negative electrode plate is formed in the same manner as the lead-acid battery A1. Lead-acid batteries D1 and D2 are assembled in the same manner as lead-acid battery A1, except that the obtained negative electrode plate is used.

<<Lead-acid batteries E1 and E2>>
Only carbon black (Ketjenblack (registered trademark)) is used as the carbon material. In this lead-acid battery, the content of the second carbon material is set to 0.2% by mass. Other than these, the negative electrode plate is formed in the same manner as the lead-acid battery D1. A lead-acid battery E1 is assembled in the same manner as the lead-acid battery A1, except that the obtained negative electrode plate is used.

A negative electrode plate is formed in the same manner as in the lead-acid battery E1, except that the content of the second carbon material is 0.4% by mass. A lead-acid battery E2 is assembled in the same manner as the lead-acid battery A1, except that the obtained negative electrode plate is used.

《Lead storage battery E3》
Only carbon black (Ketjenblack (registered trademark)) is used as the carbon material. In this lead-acid battery, the content of the second carbon material is set to 0.4% by mass. Other than these, the negative electrode plate is formed in the same manner as the lead-acid battery D2. A lead-acid battery E3 is assembled in the same manner as the lead-acid battery A1 except that the obtained negative electrode plate is used.

[Evaluation 1: Coatability]
A negative electrode paste is prepared by mixing the components of the negative electrode material using a mixer (manufactured by Dalton). Then, the negative electrode paste is applied to the current collector using a paster (manufactured by Winkel). The conditions during application are evaluated according to the following criteria.
A: The current collector coated with the negative electrode paste can be obtained at a production rate of 15 or more sheets per minute without the paste coming off from the lattice of the current collector.
B: The current collector coated with the negative electrode paste cannot be obtained at a production rate of 15 or more sheets per minute without the paste coming off from the lattice of the current collector.

[Evaluation 2: Storage performance of unformed negative electrode plate]
The content of lead carbonate contained in the negative electrode material when the unformed negative electrode plate is stored is determined by the following procedure.
First, an unformed negative electrode plate is aged for 2 days at a temperature of 35° C. and a relative humidity of 90%, dried at 60° C. for 6 hours, and then stored in the atmosphere for 3 weeks. About 5 g of the negative electrode material is sampled from the negative electrode plate after storage, and the mass W thereof is measured and then pulverized. The pulverized sample is immediately dropped into 50 mL of a 20% by mass perchloric acid aqueous solution at normal temperature (25° C.) and left for 10 minutes. The total mass m5 of the sample and the perchloric acid aqueous solution immediately before dropping and the total mass m6 of the sample and the perchloric acid aqueous solution after standing for 10 minutes are measured. At this time, the amount of decrease in mass ΔW=m6−m5 is obtained, and the lead carbonate content c3 (% by mass) in the negative electrode material is calculated by the following formula.
c3 = ΔW x ((M3/M4)/W) x 100
Here, M3 is the molecular weight of lead carbonate (PbCO ₃ ) and M4 is the molecular weight of carbon dioxide (CO ₂ ). A value of M3/M4=6.07 is used.

Then, based on the value of the carbonate content c3, the storage performance of the unformed negative electrode plate is evaluated according to the following criteria. It should be noted that the smaller the carbonate content M, the better the storage performance.
A: The carbonate content c3 is less than 20% by mass.
B: Carbonate content c3 is 20% by mass or more.

[Evaluation 3: Cycle life performance]
A cycle life test is performed on three of the four lead-acid batteries produced. In the cycle life test, the following discharge and charge cycles are repeated in a water bath at 35°C. At this time, every 100 cycles, the battery is discharged at a current of 40 A at 30° C. to a final voltage of 1.70 V, and the discharge capacity at this time is obtained.
Discharge: Discharge at a current of 50A for 3 hours.
Charging: Charge for 5 hours at a current of 37.5A.

An average discharge capacity is obtained from discharge capacities of three lead-acid batteries measured every 100 cycles. The cycle life performance is evaluated by the number of cycles T obtained as follows at the time t when the average discharge capacity falls below 75% of the nominal capacity of 200 Ah (that is, 150 Ah). A case where the number of cycles T is 1450 or more is judged to provide high cycle life performance.

The number of cycles T is obtained from the average discharge capacity Q1 at the time t when the average discharge capacity falls below 150 Ah for the first time and the average discharge capacity Q2 in the discharge test 100 cycles before that, according to the following formula.
T = t - (150 - Q1) / (Q2 - Q1) x 100

Table 1 shows the results of lead-acid batteries A1 to A8, B1 to B8, D1 to D2, and E1 to E3. FIG. 3 shows the results of cycle life performance among the results of A1 to A8 and B1 to B8 in Table 1. In FIG.

As shown in Table 1 and FIG. ³ , when the density of the negative electrode material is less than 3.8 g/cm The cycle life does not change so much between the case of using both, and all are less than 1450 cycles, which is insufficient (A1, A7, A8, B1, B7, B8). On the other hand, when the density of the negative electrode material is 3.8 g / cm ³ or more, when combining the first carbon material and the second carbon material whose powder resistance ratio is within a specific range, the second carbon material is included Despite the small amount, cycle life performance comparable to the case of using the second carbon material alone (B2-B6) is obtained (A2-A6). This is probably because the combination of the first carbon material and the second carbon material facilitates the formation of many conductive networks in the negative electrode material.

As shown in Table 1, when the second carbon material is used alone, the density of the negative electrode material increases (specifically, 3.7 g/cm ³ or more or 3.8 g/cm ³ or more). ), the negative electrode paste cannot be mechanically applied (B1-B6). In addition, in the batteries B1 to B6, the storage performance of the unformed negative electrode plate is low. On the other hand, the density of the negative electrode material can be increased to 3.7 g/cm ³ or more or 3.8 g/cm ³ or more by using together the first carbon material and the second carbon material having a powder resistance ratio within a specific range. Even in the case of , machine application is possible (A1 to A6). This is probably because in the batteries A1 to A5, by satisfying the specific powder resistance ratio R2/R1, the surface condition of each carbon material is optimized and solvent adsorption is moderately suppressed. In Battery A6, the storage performance of the unformed negative electrode plate is degraded. From the viewpoint of suppressing deterioration in storage performance, the density of the negative electrode material is preferably less than 4.7 g/cm ³ .

《Lead-acid batteries A11 to A16》
The amount of barium sulfate to be added is adjusted so that the content of barium sulfate in the previously chemically formed negative electrode material reaches the design value shown in Table 2. Other than this, lead-acid batteries A11 to A16 are assembled in the same manner as lead-acid battery A1 except that a negative plate is produced in the same manner as lead-acid battery A3 and the resulting negative plate is used. The design value of the density of the negative electrode material in these lead-acid batteries and lead-acid battery A3 is 4.1 g/cm ³ .

《Lead-acid batteries B11 to B16》
The amount of barium sulfate to be added is adjusted so that the content of barium sulfate in the previously chemically formed negative electrode material reaches the design value shown in Table 2. Other than this, lead-acid batteries B11 to B16 are assembled in the same manner as lead-acid battery A1, except that a negative plate is produced in the same manner as lead-acid battery B3, and the resulting negative plate is used. The design value of the density of the negative electrode material in these lead-acid batteries and lead-acid battery B3 is 4.1 g/cm ³ .

Lead-acid batteries A11 to A16 and B11 to B16 are evaluated in the same manner as lead-acid battery A1. Also, the content of barium sulfate in the negative electrode material is measured by the procedure described above. These evaluation results are shown in Table 2. Table 2 also shows the results of lead-acid batteries A3 and B3. The cycle life performance results of Table 2 are shown in FIG.

As shown in Table 2 and FIG. 4, the content of barium sulfate in the negative electrode material is 0.2% by mass or more and 0.7% by mass or less, and the powder resistance ratio is a specific range First carbon When the material and the second carbon material are combined, despite the small content of the second carbon material, it is comparable to the case of using the second carbon material alone (B12 to B15, B3), and 1450 cycles Higher cycle life performance than above is obtained (A12 to A15, A3). The high cycle life performance of these batteries can be obtained by combining the first carbon material and the second carbon material and by adjusting the content of barium sulfate in the negative electrode material to an appropriate range. It is believed that this is because the electron conductivity between particles is not hindered, and even if a deep discharge is performed, the lead sulfate is easily reduced during charging, and the charging is not hindered. From the viewpoint of obtaining higher cycle life performance, the content of barium sulfate is preferably 0.2 to 0.6% by mass.

In lead-acid batteries B11 to B16 and B3, the applicability evaluation was B, and mechanical application was not possible when mixing the constituent components of the negative electrode material. Compared to these batteries, lead-acid batteries A11 to A16 and A3 have remarkably improved coating properties.

《Lead-acid batteries A21 to A34》
Adjust the amount, specific surface area, and/or average aspect ratio of each carbon material used, and, if necessary, the average particle size _D50 of each carbon material. Instead of Ketjenblack, lead-acid battery A27 uses acetylene black, and lead-acid batteries A33 and A34 use activated carbon. Thus, the powder resistance ratio R2/R1 is changed as shown in Table 3. Except for these, a negative electrode plate is produced in the same manner as the lead-acid battery A3. Lead-acid batteries A21 to A34 are assembled in the same manner as lead-acid battery A1, except that the obtained negative electrode plate is used. The design value of the density of the negative electrode material in these lead-acid batteries is 4.1 g/cm ³ as in lead-acid battery A3.

《Lead-acid batteries A41 to A43》
Adjust the amount, specific surface area, and/or average aspect ratio of each carbon material used, and, if necessary, the average particle size _D50 of each carbon material. In the lead-acid battery A43, acetylene black is used instead of ketjen black. Thus, the powder resistance ratio R2/R1 is changed as shown in Table 3. Other than these, lead-acid batteries A41 to A43 are assembled in the same manner as lead-acid battery A1 except that a negative plate is produced in the same manner as lead-acid battery A1, and the resulting negative plate is used. However, the design value of the density of the negative electrode material in these lead-acid batteries is 4.7 g/cm ³ as in lead-acid battery A6.

The lead-acid batteries A21 to A34 and A41 to A43 are evaluated for evaluation 1 and evaluation 2 in the same manner as the lead-acid battery A1. Table 3 shows the evaluation results. Table 3 also shows the results of lead-acid batteries A3 and A6.

As shown in Table 3, when the powder resistance ratio R2/R1 is more than 15 and less than 230, high cycle life performance is obtained. Moreover, when it is less than 230, the applicability of the negative electrode paste is high. It is considered that the reason why the high cycle life performance is obtained in such a range of the powder resistance ratio is that many conductive networks are formed in the negative electrode material. In addition, the reason why the negative electrode paste can be applied is improved is that when the powder resistance ratio R2/R1 is within the above range, the surface state of each carbon material is optimized and the adsorption of the solvent is appropriately suppressed. It is considered to be a thing. From the viewpoint of obtaining higher cycle life performance, the R2/R1 ratio is preferably 80 or more and less than 230, or 80 or more and 220 or less. From the viewpoint of improving the storage performance of the unformed negative electrode plate, the negative electrode material preferably has a density of less than 4.7 g/cm ³ and a specific surface area ratio S2/S1 of 350 or less. preferable. This is because when the specific surface area ratio S2/S1 exceeds 350, the amount of solvent adsorbed on the surface of the carbon material increases depending on the surface state of the carbon material mixed in the paste. This is because the amount of roots must be reduced.

The lead-acid battery according to one aspect of the present invention is applicable to valve-regulated and liquid-type lead-acid batteries, and can be used as a starting power source for automobiles or motorcycles, for storing natural energy, and for electric vehicles (forklifts, etc.). It can be suitably used as a power supply for industrial power storage devices and the like.

1: Lead storage battery 2: Negative electrode plate 3: Positive electrode plate 4: Separator 5a: Negative electrode strap 5b: Positive electrode strap 6a: Negative electrode column 6b: Positive electrode column 10: Battery case 11: Electrode plate group 12: Electrolyte

Claims (6)

A lead-acid battery,
The lead-acid battery includes a negative plate and a positive plate,
The negative electrode plate includes a negative electrode material containing a carbon material and barium sulfate,
The carbon material includes a first carbon material having a particle size of 32 μm or more and a second carbon material having a particle size of less than 32 μm,
The second carbon material contains at least carbon black,
The content of the first carbon material in the negative electrode material is 0.05% by mass or more and 1.5% by mass or less,
The content of the second carbon material in the negative electrode material is 0.1% by mass or more and 1% by mass or less,
The ratio of the powder resistance R2 of the second carbon material to the powder resistance R1 of the first carbon material: R2/R1 is more than 15 and less than 230,
The content of barium sulfate in the negative electrode material is 0.2% by mass or more and 0.7% by mass or less,
The lead-acid battery, wherein the negative electrode material has a density of 4.1 g/cm ³ or more. A lead-acid battery,
The lead-acid battery includes a negative plate and a positive plate,
The negative electrode plate includes a negative electrode material containing a carbon material and barium sulfate,
The carbon material includes a first carbon material having a particle size of 32 μm or more and a second carbon material having a particle size of less than 32 μm,
The second carbon material contains at least carbon black,
The content of the first carbon material in the negative electrode material is 0.05% by mass or more and 1.5% by mass or less,
The content of the second carbon material in the negative electrode material is 0.1% by mass or more and 1% by mass or less,
The ratio of the powder resistance R2 of the second carbon material to the powder resistance R1 of the first carbon material: R2/R1 is 80 or more and 220 or less,
The content of barium sulfate in the negative electrode material is 0.2% by mass or more and 0.7% by mass or less,
The lead-acid battery, wherein the negative electrode material has a density of 3.8 g/cm ³ or more. The lead-acid battery according to claim 2, wherein the negative electrode material has a density of 4.1 g/cm3 ^or more. The lead-acid battery according to any one of claims 1 to 3, wherein the negative electrode material has a density of less than 4.7 g/cm ³ . 5. The lead-acid battery according to claim 4, wherein the ratio of the specific surface area S2 of said second carbon material to the specific surface area S1 of said first carbon material: S2/S1 is 350 or less. The lead-acid battery according to any one of claims 1 to 5 , wherein said first carbon material contains at least graphite.

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