JP2023046006A - Lead-acid battery - Google Patents

Abstract

To provide a lead-acid battery capable of exhibiting an excellent IS life performance.SOLUTION: A lead-acid battery includes a positive electrode plate, a negative electrode plate, and a separator interposed between the electrode plates. The negative electrode plate includes a negative electrode material containing barium sulfate particles. For D10, D50, and D90 in a volume-based particle size distribution of the barium sulfate particles, a span value represented by (D90-D10)/D50 is 2.78 or less. The separator includes a crystalline region and an amorphous region. In an X-ray diffraction spectrum of the separator, a crystallinity represented by 100×Ic/(Ic+Ia) is 20% or more, where Ic is an integration intensity of a diffraction peak with the maximum peak height, among diffraction peaks corresponding to the crystalline region, Ia is the integration intensity of a halo corresponding to the amorphous region. In the separator, a total volume Vt of pores having a pore size of 0.005-10 μm is 0.8 cm3/g or more.SELECTED DRAWING: Figure 1

Description

The present invention relates to lead-acid batteries.

A lead-acid battery includes a positive plate and a negative plate, a separator interposed therebetween, and an electrolyte. One of the typical uses of lead-acid batteries is for automobiles. In automotive applications, the electrical load is increasing along with the recent improvement in performance, and lead-acid batteries are required to have even higher performance. Therefore, there is a demand for a battery design that considers the effects of all the constituent elements of a lead-acid battery, including improvements in constituent elements such as separators and electrode plates.

For example, US Pat. No. 6,200,000 discloses a separator for a lead-acid battery comprising a polyolefin microporous membrane, said polyolefin microporous membrane being polyethylene, preferably ultra-high molecular weight polyethylene, a particulate filler, and a treated a plasticizer, wherein the particulate filler is present in an amount greater than or equal to 40% by weight, and wherein the polyethylene comprises a plurality of extended chain crystals (shish-forming) and a plurality of folded chain crystals (kebab-forming) A separator is proposed comprising a shish kebab-forming polymer, wherein the average repetition or period of said kebab formation is from 1 nm to 150 nm, preferably less than 120 nm.

Patent Document 2 discloses a lead-acid battery including a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolytic solution, wherein the negative electrode contains a raw material of a negative electrode active material and barium. Particles containing lead Suggest a battery.

Patent document 3 contains barium sulfate, the barium sulfate includes at least a first particle group and a second particle group, and the first particle group has a primary particle size of 10 μm or less and an average value of 0.001 μm or less. 3 μm or more and 0.9 μm or less, the primary particle diameter of the second particle group is 10 μm or less and the average value is 2 μm or more and 5 μm or less, and the first particle group is, on a volume frequency basis, relative to the total amount of barium sulfate , 28% or more and 72% or less.

Japanese Patent Publication No. 2019-514173 WO2018/100635 JP 2015-109171 A

In lead-acid batteries, sulfate ions, which have a large specific gravity, descend during charging, and stratification is likely to occur in which a difference in specific gravity of the electrolyte solution (that is, a difference in concentration of sulfuric acid) occurs between the upper and lower parts of the battery case. Stratification becomes noticeable when lead-acid batteries are used in an undercharged state called Partial State Of Charge (PSOC). For example, in idling stop (IS) (also referred to as idle reduction) applications such as idling stop system vehicles or charge control applications, lead-acid batteries are used in PSOCs, so stratification tends to be noticeable. When the stratification becomes significant, the negative electrode plate deteriorates, and the life performance (also referred to as IS life performance) of the lead-acid battery when used in PSOC decreases.

When the pore volume of the separator is increased, the diffusibility of the electrolytic solution is improved, which is expected to be advantageous from the viewpoint of suppressing stratification. However, since the contact area with the electrolytic solution increases, oxidation deterioration of the separator is likely to progress. Damage to the separator causes a short circuit and shortens the service life, so the effect of improving the IS service life performance is limited.

In addition, lead sulfate is formed on the negative plate of a lead-acid battery during discharge. If the particles of lead sulfate are coarsened, it becomes difficult for lead sulfate to be reduced to lead during charging, resulting in a decrease in charge acceptance. This further promotes stratification and decreases capacity. From this point as well, the IS life performance is lowered.

One aspect of the present disclosure is a lead-acid battery comprising:
The lead-acid battery includes at least one cell including an electrode group and an electrolyte,
The electrode plate group includes a positive electrode plate, a negative electrode plate, and a separator interposed between the positive electrode plate and the negative electrode plate,
The negative plate comprises a negative electrode material containing barium sulfate particles,
In the volume-based particle size distribution of the barium sulfate particles, when the particle diameters at which the cumulative frequency is 10%, 50%, and 90% are D10, D50, and D90, respectively, (D90-D10)/D50 span value is 2.78 or less,
the separator includes a crystalline region and an amorphous region;
In the X-ray diffraction spectrum of the separator, the crystallinity indicated by 100×I _c /(I _c +I _a ) is 20% or more,
I _c is the integrated intensity of the diffraction peak having the maximum peak height among the diffraction peaks corresponding to the crystalline region;
I _a is the integrated intensity of the halo corresponding to the amorphous region;
The separator relates to a lead-acid battery, wherein the total volume Vt of pores having a pore diameter of 0.005 μm or more and 10 μm or less is 0.8 cm ³ /g or more.

A lead-acid battery with excellent IS life performance can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS It is a partially cutaway perspective view which shows the external appearance and internal structure of the lead storage battery which concerns on one Embodiment of this invention. 4 is an X-ray diffraction spectrum of the lead-acid battery separator of the lead-acid battery E1 of the example.

Various studies have been made for the purpose of improving the IS life performance of lead-acid batteries. Using a separator with a large pore volume is effective to some extent in suppressing stratification. This is because, in IS applications, constant voltage charging is performed and the flowing current increases, gas is generated, and the effect of mixing the electrolytic solution is obtained when the gas diffuses through many pores of the separator. However, the trade-off is that the contact area between the separator and the gas increases, and the chances of contact increase, which facilitates the oxidative deterioration of the separator. In addition, as the softening of the positive electrode material progresses, the separated positive electrode material is likely to break when coming into contact with the separator. From these points of view, the short circuit chance of the separator increases and the IS life performance decreases. Therefore, if oxidation deterioration can be suppressed while maintaining a large pore volume of the separator, it is effective in improving the IS life performance.

In the negative plate, if coarsening of lead sulfate generated during discharge can be suppressed, charge acceptance will be improved, and lead sulfate can be smoothly reduced to lead during charge. When the charge-discharge reaction on the negative electrode plate progresses more uniformly over the entire electrode plate, the charge-discharge reaction on the positive electrode plate tends to progress more uniformly. Therefore, the stratification becomes difficult to progress and the decrease in capacity is suppressed, which is considered to be advantageous in terms of improving the IS life performance.

The negative electrode material may contain barium sulfate particles as an additive. In this case, lead sulfate is formed with barium sulfate particles serving as nuclei on the negative plate during discharge. Therefore, generation of coarse lead sulfate can be reduced to some extent during discharge. However, if there is a large variation in the particle size of the barium sulfate that forms the core, there is a tendency for the variation in the particle size of the produced lead sulfate to increase. If the particle size of lead sulfate varies greatly, the reactivity during charging will vary.

In view of the above, a lead-acid battery according to one aspect of the present invention includes at least one cell including a plate assembly and an electrolyte. The electrode plate group includes a positive electrode plate, a negative electrode plate, and a separator interposed between the positive electrode plate and the negative electrode plate. The negative plate comprises a negative electrode material comprising barium sulfate particles. In the volume-based particle size distribution of barium sulfate particles, the particle diameters at which the cumulative frequencies are 10%, 50% and 90% are defined as D10, D50 and D90, respectively. At this time, the span value represented by (D90-D10)/D50 is 2.78 or less. The separator also includes crystalline regions and amorphous regions. In the X-ray diffraction (XRD) spectrum of the separator, the crystallinity indicated by 100×I _c /(I _c +I _a ) is 20% or more. Here, I _c is the integrated intensity of the diffraction peak having the maximum peak height among the diffraction peaks corresponding to the crystalline region (hereinafter sometimes referred to as the first diffraction peak), and I _a is the integrated intensity of the halo corresponding to the crystalline region. The total volume Vt of pores having a pore diameter of 0.005 μm or more and 10 μm or less is 0.8 cm ³ /g or more. Hereinafter, a pore having a pore diameter of 0.005 μm or more and 10 μm or less may be referred to as a first pore. Also, the total Vt of the volumes of the first pores may simply be referred to as the first pore volume Vt.

The span value of barium sulfate particles represents the degree of variation in particle size. When the variation in the particle size of the barium sulfate particles increases, lead sulfate with a large particle size is less likely to be reduced to lead, while lead sulfate with a small particle size is smoothly reduced. Even if the battery is charged for the same period of time, the amount of lead sulfate reduced to lead decreases, resulting in a decrease in charge capacity. As a result, the discharge reaction also varies, and the discharge capacity also decreases. In addition, there is a tendency that the IS life performance decreases as the variation in the particle size of the barium sulfate particles increases. In particular, when the span value exceeds 2.78, the deterioration of IS life performance tends to become remarkable. The tendency for the IS life performance to decrease as the span value increases is also seen when the crystallinity of the separator is 20% or more.

However, when the span value of the barium sulfate particles in the negative electrode material is 2.78 or less, the crystallinity is 20% or more, and the total volume Vt of the first pores (first pore volume Vt) is 0 Combining a separator with a density of 0.8 cm ³ /g or more markedly improves the IS life performance.

More specifically, first, since the span value of the barium sulfate particles is 2.78 or less, variation in particle size of lead sulfate particles formed during discharge is relatively small. Therefore, during charging, variations in the progress of the reduction reaction from lead sulfate to lead are reduced, the charge acceptance is improved, and the charging reaction occurs more uniformly. For the same charging time, more lead sulfate can be reduced to lead than when the span value exceeds 2.78. In addition, since the variation in the charging reaction on the negative electrode plate is reduced, the variation in the charging reaction on the positive electrode plate is also reduced, and the charging reaction as a whole progresses easily.

At that time, when the total Vt of the volume of the first pores in the separator (first pore volume Vt) is 0.8 cm ³ /g or more, high diffusibility of the electrolytic solution can be obtained and the resistance of the separator can be lowered. can be suppressed. Therefore, the effect of suppressing stratification increases. Therefore, the charge/discharge reaction in the negative electrode proceeds smoothly, together with the charge characteristics improved by reducing the variation in the particle size of the barium sulfate particles. However, when the first pore volume Vt is within the above range, the contact area with the electrolytic solution is increased, so that the oxidation deterioration of the separator tends to progress easily. In a lead-acid battery, when the separator is oxidatively degraded, the flexibility is reduced, cracks are generated, and short circuiting occurs, resulting in the end of the life. Even if the stratification can be reduced, the effect of improving the IS life performance is limited. On the other hand, in the aspect of the present invention, since the degree of crystallinity is 20% or more, the oxidation resistance of the separator itself can be enhanced. Therefore, oxidative deterioration of the separator is reduced, which suppresses the deterioration of IS life performance due to short circuits. The accompanying effect of improving the IS life performance is sufficiently exhibited. As a result of these, excellent IS life performance can be ensured.

Note that when the first pore volume Vt is less than 0.8 cm ³ /g, even if the degree of crystallinity is changed, the IS life performance hardly changes. In this case, since the separator has a small surface area, the contact with the electrolytic solution is reduced, and oxidative deterioration is suppressed. Therefore, it is considered that increasing the crystallinity of the separator does not affect the IS life performance. Thus, when the first pore volume Vt is less than 0.8 cm ³ /g and when it is 0.8 cm ³ /g or more, the behavior of the IS life performance when changing the crystallinity of the separator is completely different. different.

A separator for a lead-acid battery has a relatively large thickness, unlike a separator for a lithium-ion secondary battery. In addition, the thicker the separator, the more difficult it becomes to increase the degree of crystallinity, and the higher the degree of crystallinity, the harder and more brittle the separator tends to be. From this point of view, the degree of crystallinity has not been controlled in conventional separators for lead-acid batteries. The crystallinity of separators for conventional lead-acid batteries tends to be relatively low, eg, about 18% or less. Contrary to such conventional wisdom, according to the lead-acid battery of one aspect of the present invention, when the first pore volume Vt is 0.8 cm ³ /g or more, the separator has a degree of crystallinity of 20% or more. , and the span value of the barium sulfate particles is 2.78 or less.

The total Vt of the volume of the first pores in the separator (first pore volume Vt) is the first pores in the separator (pores having a pore diameter of 0.005 μm or more and 10 μm or less) obtained by the mercury porosimetry. is the sum of the volumes of

The volume-based particle size distribution of the barium sulfate particles is a volume-based particle size distribution measured by a laser diffraction or scattering type particle size distribution analyzer. The particle diameters when the accumulation (integrated value) of the frequency in this volume-based particle size distribution is 10%, 50% and 90% are D10, D50 and D90, respectively. A particle diameter D50 corresponding to 50% of the integrated value in the volume-based particle size distribution is also called a median diameter. In this specification, the particle size of barium sulfate particles means the particle size of primary particles.

From the viewpoint of easily obtaining higher IS life performance, the span value is preferably 2.75 or less, more preferably 2.45 or less.

The first pore volume Vt is preferably 0.90 cm ³ /g or more. When the crystallinity of the separator is less than 20%, the IS life performance is high when the first pore volume Vt is 0.8 cm ³ /g, but the span value is small and Vt is 0.8 cm ³ /g. Even if it is larger, the IS life performance decreases. This is because, in addition to the low degree of crystallinity, the oxidation deterioration of the separator becomes conspicuous due to the increase in Vt. On the other hand, when the crystallinity is 20% or more, the IS life performance increases as the span value of the barium sulfate particles decreases. In addition, high IS life performance can be easily obtained from the point that higher oxidation resistance of the separator can be obtained.

The degree of crystallinity may be 40% or less. In this case, it is easy to secure the flexibility of the separator, and in addition, it is easy to manufacture.

The separator preferably contains a polyolefin, more preferably a polyolefin containing at least ethylene units. Such a separator is easily deteriorated by oxidation, but the degree of crystallinity can be increased relatively easily. If the separator comprises a polyolefin containing at least ethylene units, the first diffraction peak corresponds to the (110) plane due to the crystalline regions.

The thickness of the separator is preferably 100 μm or more and 300 μm or less. When the thickness is within such a range, the effect of suppressing oxidation deterioration of the separator is further enhanced, and the IS life performance can be further improved.

The separator preferably contains oil. In this case, the effect of suppressing oxidation deterioration of the separator is further enhanced, and higher IS life performance can be secured.

The lead-acid battery may be a valve regulated battery, but is preferably a flooded battery (vented battery). A valve regulated lead-acid battery is sometimes called VRLA (Valve Regulated Lead-Acid Battery).

In this specification, the vertical direction of a lead-acid battery or components of a lead-acid battery (electrode plate, container, separator, etc.) means the vertical direction of the lead-acid battery when the lead-acid battery is used. Each of the positive electrode plate and the negative electrode plate has an ear portion for connection with an external terminal. there is

Hereinafter, lead-acid batteries according to embodiments of the present invention will be described more specifically with reference to the drawings. However, the present invention is not limited to the following embodiments.

(separator)
The separator includes a crystalline region in which the molecules of the constituent material of the separator are arranged relatively regularly (that is, highly ordered) and an amorphous region in which the molecules are poorly arranged. Therefore, in the XRD spectrum of the separator, a diffraction peak due to the crystalline region is observed, and scattered light due to the amorphous region is observed as a halo. Excellent IS life performance is obtained when the degree of crystallinity represented by 100×I _c /(I _c +I _a ) is 20% or more in the XRD spectrum of the separator. Here, _Ic is the integrated intensity of the diffraction peak (first diffraction peak) having the maximum peak height among the diffraction peaks corresponding to the crystalline region, and _Ia is the halo corresponding to the amorphous region. is the integrated intensity of

For example, in the XRD spectrum of a separator containing a polyolefin containing ethylene units, a diffraction peak corresponding to the (110) plane of the crystalline region is observed in the range of 2θ from 20° to 22.5°. A diffraction peak corresponding to the (200) plane is observed in the range of 2θ from 23° to 24.5°. A halo in the amorphous region is observed in the range of 2θ from 17° to 27°. Among the diffraction peaks due to the crystalline region, the diffraction peak corresponding to the (110) plane has the highest peak height and corresponds to the first diffraction peak.

The crystallinity is 20% or more, and may be 23% or more or 25% or more from the viewpoint of ensuring higher IS life performance. The crystallinity of the separator may be 40% or less, 35% or less, or 30% or less. When the degree of crystallinity is within such a range, it is easy to ensure the flexibility of the separator, and the production is easy.

The crystallinity of the separator is 20% or more (or 23% or more) and 40% or less, 20% or more (or 23% or more) and 35% or less, 20% or more (or 23% or more) and 30% or less, 25% or more and 40%. % or less (or 35% or less), or 25% or more and 30% or less.

The integrated intensity of the diffraction peaks and halos is obtained by fitting the diffraction peaks due to the crystalline regions and the halos due to the amorphous regions in the XRD spectrum of the separator. Using the obtained integrated intensity _Ic of the first diffraction peak and the obtained integrated intensity _Ia of the halo, the degree of crystallinity is obtained from the above formula.

The separator has a first pore volume Vt of 0.8 cm ³ /g or more. By setting the first pore volume Vt within such a range, high diffusibility of the electrolytic solution can be obtained, and the resistance of the separator can be kept low. Therefore, excellent IS life performance is obtained. From the viewpoint of ensuring higher IS life performance, the first pore volume Vt is preferably 0.90 cm ³ /g or more. The first pore volume Vt is, for example, 2.2 cm ³ /g or less. The first pore volume Vt is preferably 2.0 cm 3 /g or less, more preferably 1.6 cm ³ /g or less, or 1.6 cm 3 /g or less, or 1.6 cm ³ /g or less, or 1.6 cm 3 /g or less. 2 cm ³ /g or less is more preferable.

The first pore volume Vt is 0.8 cm ³ /g or more (or 0.90 cm ³ /g or more), 2.2 cm ³ /g or less, 0.8 cm ³ /g or more (or 0.90 cm ³ /g or more) 2.0 cm ³ /g or less, 0.8 cm ³ /g or more (or 0.90 cm ³ /g or more), 1.6 cm ³ /g or less, or 0.8 cm ³ /g or more (or 0.90 cm ³ /g or more) ) may be 1.2 cm ³ /g or less.

The separator includes a polymer material (hereinafter also referred to as base polymer). Since the separator contains crystalline regions, the base polymer usually contains a crystalline polymer. The separator includes, for example, polyolefin. A polyolefin is a polymer containing at least olefinic units (that is, a polymer containing at least monomeric units derived from an olefin).

A polyolefin and another base polymer may be used in combination as the base polymer. The ratio of polyolefin to the entire base polymer contained in the separator is, for example, 50% by mass or more, may be 80% by mass or more, or may be 90% by mass or more. The proportion of polyolefin is, for example, 100% by mass or less. The base polymer may consist of polyolefin only. When the ratio of polyolefin is so high, the oxidation resistance of the separator tends to be low, but even in such a case, the degree of crystallinity is within the above range, so high IS life performance is ensured. be able to.

Polyolefins include, for example, homopolymers of olefins, copolymers containing different olefinic units, and copolymers containing olefinic units and copolymerizable monomeric units. A copolymer containing olefin units and copolymerizable monomer units may contain one or more olefin units. Further, the copolymer containing olefin units and copolymerizable monomer units may contain one or more copolymerizable monomer units. A copolymerizable monomer unit is a monomer unit derived from a polymerizable monomer other than an olefin and copolymerizable with an olefin.

Polyolefins include, for example, polymers containing at least C _2-3 olefins as monomer units. The C _2-3 olefin includes at least one selected from the group consisting of ethylene and propylene. More preferred polyolefins are, for example, polyethylene, polypropylene, and copolymers containing C _2-3 olefins as monomer units (eg, ethylene-propylene copolymers). Among polyolefins, it is preferable to use polyolefins containing at least ethylene units (polyethylene, ethylene-propylene copolymer, etc.). Polyolefins containing ethylene units (polyethylene, ethylene-propylene copolymers, etc.) may be used in combination with other polyolefins.

The separator preferably contains oil. When the separator contains oil, the effect of suppressing oxidative deterioration of the separator can be further enhanced, so that higher IS life performance can be ensured. Oil refers to a hydrophobic substance that is liquid at room temperature (20° C. or higher and 35° C. or lower) and separates from water. Oils include naturally derived oils, mineral oils, and synthetic oils. Mineral oil, synthetic oil and the like are preferable as the oil. Examples of oils include paraffin oil and silicone oil. The separator may contain one type of oil or may contain two or more types in combination.

The content of oil in the separator may be 11% by mass or more or 12% by mass or more. The oil content may be 18% by mass or less. When the oil content is within this range, the effect of suppressing oxidative deterioration of the separator is further enhanced. Also, the resistance of the separator can be kept relatively low.

The separator may be sheet-like. Also, a sheet that is bent into a bellows shape may be used as the separator. The separator may be shaped like a bag. Either one of the positive electrode plate and the negative electrode plate may be wrapped in a bag-shaped separator.

The separator may or may not have ribs. A separator having ribs includes, for example, a base portion and ribs erected from the surface of the base portion. The ribs may be provided only on one surface of the separator or each base portion, or may be provided on both surfaces. In addition, the base portion of the separator is a portion excluding projections such as ribs among constituent portions of the separator, and refers to a sheet-like portion that defines the outer shape of the separator.

The thickness of the separator is, for example, 90 μm or more. From the viewpoint of obtaining higher IS life performance, the thickness is preferably 100 μm or more or 150 μm or more. The thickness of the separator is, for example, 300 μm or less. From the viewpoint of keeping the resistance of the separator low, the thickness of the separator may be 250 μm or less or 200 μm or less. The thickness of the separator means the average thickness of the portion of the separator facing the electrode material. When the separator has a base portion and ribs erected from at least one surface of the base portion, the thickness of the separator is the average thickness of the base portion. When a sticking member (mat, pasting paper, etc.) is stuck to the separator, the thickness of the sticking member is not included in the thickness of the separator.

The thickness of the separator is 90 μm or more and 300 μm or less (or 250 μm or less), 90 μm or more and 200 μm or less, 100 μm or more (or 150 μm or more) and 300 μm or less, 100 μm or more (or 150 μm or more) and 250 μm or less, or 100 μm or more (or 150 μm or more) and 200 μm. It may be below.

When the separator has ribs, the rib height may be 0.05 mm or more. Also, the rib height may be 1.2 mm or less. The height of the rib is the height of the portion that protrudes from the surface of the base portion (protrusion height).

The height of the rib provided in the region of the separator facing the positive electrode plate may be 0.4 mm or more. The height of the rib provided in the region of the separator facing the positive electrode plate may be 1.2 mm or less.

For the separator, for example, a resin composition containing a base polymer, a pore-forming agent, and a penetrating agent (surfactant) is extruded into a sheet, stretched, and then at least part of the pore-forming agent is removed. obtained by Removal of at least a portion of the pore-forming agent forms micropores in the matrix of the base polymer. The separator (or the resin composition used for producing the separator) may contain inorganic particles. After removing the pore-forming agent, the sheet-like separator is dried if necessary. For example, the degree of crystallinity is adjusted by adjusting at least one selected from the group consisting of the cooling rate of the sheet during extrusion, the draw ratio during stretching, and the temperature during drying. . For example, the degree of crystallinity tends to increase when the sheet is quenched during extrusion molding, the draw ratio is increased, or the temperature during drying is decreased. The stretching treatment may be carried out by biaxial stretching, but is usually carried out by uniaxial stretching. The sheet-like separator may be bent into a bellows shape or processed into a bag shape, if necessary.

In separators having ribs, the ribs may be formed into the sheet during extrusion of the resin composition. Alternatively, the ribs may be formed by pressing the sheet with a roller having grooves corresponding to the ribs after molding the resin composition into a sheet or after removing the pore-forming agent.

The pore structure and the first pore volume Vt in the separator control the affinity between the base polymer and the pore-forming agent and/or the penetrating agent, control the dispersibility of the pore-forming agent, and determine the type of inorganic particles. and/or select the particle size, select the type of penetrant, adjust the amount of the inorganic particles, the amount of the pore-forming agent, and/or the amount of the penetrant, and/or the surface of the inorganic particles can be adjusted by adjusting the amount of functional groups and/or atoms present in .

Pore-forming agents include liquid pore-forming agents and solid pore-forming agents. The pore-forming agent preferably contains at least oil. By using oil, an oil-containing separator can be obtained, and the effect of suppressing oxidative deterioration is further enhanced. The pore-forming agents may be used singly or in combination of two or more. Oil and other pore-forming agents may be used in combination. A liquid pore-forming agent and a solid pore-forming agent may be used in combination. At room temperature (20° C. or higher and 35° C. or lower), a liquid pore-forming agent is classified as a liquid pore-forming agent, and a solid pore-forming agent as a solid pore-forming agent.

As the liquid pore-forming agent, the oils mentioned above are preferred. Solid pore formers include, for example, polymer powders.

The amount of pore-forming agent in the separator may vary depending on the type. The amount of the pore-forming agent in the separator is, for example, 30 parts by weight or more per 100 parts by weight of the base polymer. The amount of the pore-forming agent is, for example, 60 parts by weight or less per 100 parts by weight of the base polymer.

For example, a separator containing oil is formed by extracting and removing a portion of the oil using a solvent from a sheet formed using oil as a pore-forming agent. A solvent is selected, for example, according to the type of oil. For example, the oil content in the separator can be adjusted by adjusting the type and composition of the solvent, extraction conditions (extraction time, extraction temperature, speed of supplying the solvent, etc.).

Surfactants as penetrants may be, for example, ionic surfactants or nonionic surfactants. Surfactants may be used alone or in combination of two or more.

The content of the penetrant in the separator is, for example, 0.01% by mass or more, and may be 0.1% by mass or more. The penetrant content in the separator may be 10% by mass or less.

As the inorganic particles, for example, ceramic particles are preferable. Ceramics constituting the ceramic particles include, for example, at least one selected from the group consisting of silica, alumina, and titania.

The content of inorganic particles in the separator may be, for example, 40% by mass or more. The content of inorganic particles is, for example, 80% by mass or less, and may be 70% by mass or less.

(separator analysis or size measurement)
(Preparation of separator)
An unused separator or a separator removed from a fully charged lead-acid battery in the initial stage of use is used for analysis or size measurement of the separator. Separators removed from lead-acid batteries are washed and dried prior to analysis or measurement.

The cleaning and drying of the separator removed from the lead-acid battery are performed according to the following procedures. The separator taken out from the lead-acid battery is immersed in pure water for 1 hour to remove the sulfuric acid in the separator. Next, the separator is taken out from the liquid in which it was immersed, left to stand in an environment of 25° C.±5° C. for 16 hours or longer, and dried.

In this specification, the fully charged state of a liquid lead-acid battery is defined by the definition of JIS D 5301:2019. More specifically, the terminal voltage (V ) or the fully charged state is the state in which the electrolyte solution density converted to temperature at 20° C. is charged three times consecutively until it shows a constant value with three significant digits. In the case of a valve-regulated lead-acid battery, a fully charged state is defined as a current (0.2 times the rated capacity value (unit: Ah) in an air tank at 25°C ± 2°C). In A), constant current constant voltage charging is performed at 2.23 V / cell, and the charging current during constant voltage charging is a value (A) that is 0.005 times the value (value in Ah) described in the rated capacity. The charging is finished when it becomes . The numerical value described as the rated capacity is a numerical value whose unit is Ah. The unit of current set based on the numerical value described as the rated capacity is A.

A fully-charged lead-acid battery is a lead-acid battery obtained by fully charging an existing chemical lead-acid battery. The lead-acid battery may be fully charged immediately after the formation as long as it is after the formation, or after some time has passed since the formation. may be used).

In this specification, the term "battery in the early stage of use" means a battery in which not much time has passed since the start of use and which has hardly deteriorated.

(XRD spectrum)
The XRD spectrum of the separator is measured by irradiating X-rays in a direction perpendicular to the surface of the separator. A sample for measurement is produced by processing the portion of the separator facing the electrode material into a strip shape. For separators with ribs, samples are prepared by processing the base portion into strips so as not to include ribs. Measurement and fitting of the XRD spectrum are performed under the following conditions.
(Measurement condition)
Measuring device: RINT-TTR2, manufactured by Rigaku Co., Ltd. Fitting: FT (step scan) method Measurement angle range: 15-35°
Step width: 0.02°
Measurement speed: 5°/min
XRD data processing: using XRD pattern analysis software (PDXL2, manufactured by Rigaku Corporation).

(First pore volume Vt)
A sample (hereinafter referred to as sample A) is prepared by processing the portion of the separator facing the electrode material into a strip of 20 mm×5 mm. In the case of a separator having ribs, sample A is produced by processing the base portion into a strip shape so as not to include ribs. For sample A, the pore size distribution is determined using a mercury porosimeter under the following conditions, and Vt is determined by totaling the volumes of the first pores.
Mercury porosimeter: Autopore IV9510, manufactured by Shimadzu Corporation Pressure range for measurement: 4 psia (≈27.6 kPa) or more and 60,000 psia (≈414 MPa) or less Pore distribution: 0.01 μm or more and 50 μm or less

(Separator thickness and rib height)
The thickness of the separator is obtained by measuring the thickness at five arbitrarily selected points in a cross-sectional photograph of the separator and averaging the thicknesses.

The height of the rib is obtained by averaging the heights from one surface of the base portion of the rib measured at 10 arbitrarily selected locations of the rib in the cross-sectional photograph of the separator.

(Oil content in separator)
A sample (hereinafter referred to as sample B) is prepared by processing the portion of the separator facing the electrode material into a strip shape. In the case of a separator having ribs, Sample B is produced by processing the base portion into a strip shape so as not to include ribs.

About 0.5 g of sample B is taken and weighed accurately to determine the initial sample mass (m0). Place the weighed sample B in an appropriately sized glass beaker and add 50 mL of n-hexane. Next, ultrasonic waves are applied to each beaker for about 30 minutes to elute the oil contained in sample B into n-hexane. Next, a sample is removed from n-hexane, dried in the air at room temperature (20° C. or higher and 35° C. or lower), and weighed to determine the mass (m1) of the sample after oil removal. Then, the oil content is calculated by the following formula. The oil content is determined for 10 samples B, and the average value is calculated. The obtained average value is taken as the oil content in the separator.
Oil content (% by mass) = (m0-m1)/m0 x 100

(Content of inorganic particles in separator)
A portion of sample B prepared in the same manner as described above is sampled, accurately weighed, placed in a platinum crucible, and heated with a Bunsen burner until white smoke is no longer emitted. Next, the resulting sample is heated in an electric furnace (550° C.±10° C. in an oxygen stream) for about 1 hour to be ashed, and the ashed matter is weighed. The ratio (percentage) of the mass of the ash to the mass of the sample B is calculated and defined as the inorganic particle content (% by mass). The content of inorganic particles is determined for 10 samples B, and the average value is calculated. Let the obtained average value be the content rate of the inorganic particle in a separator.

(Content of penetrant in separator)
A portion of Sample B prepared in the same manner as described above is sampled, weighed accurately, and dried at room temperature (20° C. or higher and 35° C. or lower) under a reduced pressure environment lower than atmospheric pressure for 12 hours or longer. The dried material is placed in a platinum cell, set in a thermogravimetry device, and heated from room temperature to 800° C.±1° C. at a temperature elevation rate of 10 K/min. The amount of weight loss when the temperature is raised from room temperature to 250°C ± 1°C is taken as the mass of the penetrant, and the ratio (percentage) of the mass of the penetrant to the mass of sample B is calculated, and the content of the above penetrant. (% by mass). As a thermogravimetry device, T.I. A. Q5000IR manufactured by Instruments is used. The penetrant content is obtained for 10 samples B, and the average value is calculated. The obtained average value is taken as the penetrant content in the separator.

(negative plate)
A negative electrode plate of a lead-acid battery is composed of a negative current collector and a negative electrode material. The negative electrode material is a portion of the negative electrode plate excluding the negative electrode current collector. In some cases, the above-described attachment member is attached to the negative electrode plate. In this case, the attachment member is included in the negative electrode plate. When the negative plate includes the sticking member, the negative electrode material is the portion of the negative plate excluding the negative current collector and the sticking member.

The negative electrode current collector can be formed in the same manner as the positive electrode current collector. At least one of the positive electrode current collector and the negative electrode current collector may be a current collector formed by an expanding process.

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 or 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. The negative electrode current collector may have lead alloy layers with different compositions, and the alloy layer may be a single layer or a plurality of layers.

The negative electrode material contained in the negative plate contains barium sulfate particles. The negative electrode material usually contains a negative electrode active material (lead or lead sulfate) that develops capacity through an oxidation-reduction reaction, and may contain an organic shrinkage agent, a carbonaceous material, and the like. The negative electrode material may contain other additives (such as reinforcing materials) as necessary.

The barium sulfate particles have a span value represented by (D90-D10)/D50 of 2.78 or less. If the span value exceeds 2.78, almost no improvement in IS life performance is obtained. From the viewpoint of obtaining higher IS life performance, the span value is preferably 2.75 or less or 2.73 or less, more preferably 2.45 or less or 2.42 or less. When combined with a separator having a first pore volume Vt of 0.8 cm ³ /g or more and a crystallinity of 20% or less, the smaller the span value of the barium sulfate particles in the negative electrode material, the higher the IS life performance. tend to become However, reducing the span value is technically difficult. The lower limit of the span value is not particularly limited, and may be 2 or more, for example.

In the negative electrode material, the barium sulfate particles have a D50 (average particle size) of 1 μm or less, may be 0.7 μm or less, or may be 0.4 μm or less. When D50 is in such a range, lead sulfate tends to grow from barium sulfate particles as nuclei, so that the span value can be easily adjusted to a suitable range. In addition, aggregation of barium sulfate particles can be easily suppressed, and handleability can be improved. The barium sulfate particles have an average particle size of, for example, 0.01 μm or more.

In the negative electrode material, the D90 of the barium sulfate particles may be 2.5 μm or less, 2.0 μm or less, or 1.7 μm or less. When D90 is in such a range, it is easy to reduce the span value. Moreover, D90 of the barium sulfate particles may be 1.0 μm or more.

In the negative electrode material, D10 of the barium sulfate particles may be 0.25 μm or less, 0.24 μm or less, or 0.22 μm or less. When D10 is in such a range, it is easy to adjust the span value to an appropriate range. Moreover, D10 of the barium sulfate particles may be 0.01 μm or more.

The content of barium sulfate particles in the negative electrode material is, for example, 0.1% by mass or more, preferably 0.5% by mass or more, or 1% by mass or more. When the content of the barium sulfate particles is within this range, an appropriate amount of barium sulfate, which forms the nuclei of lead sulfate during discharge, is present, so that the discharge reaction proceeds more uniformly. In addition, the content of barium sulfate particles in the negative electrode material is, for example, 7.5% by mass or less, preferably 5.3% by mass or less. In this case, a high initial capacity can be secured.

The content of barium sulfate particles in the negative electrode material is 0.1% by mass or more and 7.5% by mass or less (or 5.3% by mass or less), 0.5% by mass or more and 7.5% by mass or less (or 5 .3 mass % or less), or 1 mass % or more and 7.5 mass % or less (or 5.3 mass % or less).

Examples of organic shrink-proofing agents include lignin, ligninsulfonic acid, synthetic organic shrink-proofing agents (formaldehyde condensates of phenolic compounds, etc.), and the like. The negative electrode material may contain one kind or two or more kinds of organic expanders.

The content of the organic anti-shrinking agent in the negative electrode material is, for example, 0.01% by mass or more. The content of the organic shrink-proofing agent is, for example, 1.2% by mass or less.

Examples of carbonaceous materials include carbon black, graphite (artificial graphite, natural graphite, etc.), hard carbon, soft carbon, and the like. The negative electrode material may contain one type of carbonaceous material, or may contain two or more types.

The content of the carbonaceous material in the negative electrode material is, for example, 0.1% by mass or more. The content of the carbonaceous material may be, for example, 3.5% by mass or less.

Examples of reinforcing materials include fibers (inorganic fibers, organic fibers, etc.). Examples of resins (or polymers) constituting organic fibers include acrylic resins, polyolefin resins (polypropylene resins, polyethylene resins, etc.), polyester resins (including polyalkylene arylates (polyethylene terephthalate, etc.)). , and celluloses (cellulose, cellulose derivatives (cellulose ether, cellulose ester, etc.)). Celluloses also include rayon.

The content of the reinforcing material in the negative electrode material is, for example, 0.03% by mass or more. Moreover, the content of the reinforcing material in the negative electrode material is, for example, 0.6% by mass or less.

(Analysis of Negative Electrode Material or its Constituents)
A method for quantifying the organic shrinkage agent, the carbonaceous material, the barium sulfate particles, and the reinforcing material in the negative electrode material, and the measurement of the size of the barium sulfate particles are described below. Quantitative analysis of the components of the negative electrode material is performed using the negative electrode material collected from the negative electrode plate removed from the lead-acid battery in a fully charged state.

The negative electrode material is recovered from the negative plate by the following procedure. First, a fully charged lead-acid battery is disassembled to obtain a negative electrode plate to be analyzed. The obtained negative electrode plate is washed with water to remove sulfuric acid from the negative electrode plate. Washing with water is performed by pressing a pH test paper against the surface of the washed negative electrode plate until it is confirmed that the color of the test paper does not change. However, the time for washing with water shall be within 2 hours. The washed negative electrode plate is dried at 60±5° C. for about 6 hours under reduced pressure. After drying, if the negative plate contains the sticking member, the sticking member is removed from the negative plate by peeling. Next, a sample (hereinafter referred to as sample C) is obtained by separating the negative electrode material from the negative plate. Sample C is pulverized as necessary and subjected to analysis.

《Determination of organic shrinkage agents》
The pulverized sample C is immersed in a 1 mol/L NaOH aqueous solution to extract the organic shrink-proofing agent. Insoluble components are removed by filtration from the extracted NaOH aqueous solution containing the organic anti-shrinking agent, and the filtrate (hereinafter also referred to as filtrate D) is recovered.

A predetermined amount of the filtrate D is measured, desalted, concentrated and dried to obtain a powder of the organic shrink-proofing agent (hereinafter also referred to as sample E). Desalting is carried out by using a desalting column, by passing the filtrate D through an ion exchange membrane, or by placing the filtrate D in a dialysis tube and immersing it in distilled water.

The infrared spectrum of sample E, the UV-visible absorption spectrum of a solution obtained by dissolving sample E in distilled water, etc., the NMR spectrum of a solution obtained by dissolving sample F in a solvent such as heavy water, or the substance By combining the information obtained from pyrolysis GC-MS, etc., which can obtain information on individual compounds that are present, the organic expanders are identified.

An ultraviolet-visible absorption spectrum of the filtrate D is measured. From the spectral intensity, the calibration curve prepared in advance, the measured amount of filtrate D, and the mass of sample C, the content of the organic shrinkage agent 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.

<<Determination of Carbonaceous Material, Barium Sulfate Particles, and Reinforcement>>
50 mL of nitric acid having a concentration of 20% by mass is added to 10 g of the pulverized sample C and heated for about 20 minutes to dissolve the lead component as lead ions. Next, the resulting solution is filtered to remove solids such as carbonaceous materials and barium sulfate.

After dispersing the obtained solid content in water to form a dispersion, the reinforcing material is recovered from the dispersion using a sieve. The reinforcement is washed with water, dried and weighed. The ratio (percentage) of the mass of the dried product to the mass of sample C is determined. This ratio corresponds to the amount of reinforcing material in the negative electrode material.

After the reinforcing material has been removed, the dispersion is subjected to suction filtration using a membrane filter whose mass has been measured in advance, and the membrane filter is dried together with the filtered sample in a drier at 110°C ± 5°C. The obtained sample is a mixed sample of carbonaceous material and barium sulfate (hereinafter also referred to as sample F). The mass of the sample F (M _m ) is measured by subtracting the mass of the membrane filter from the total mass of the dried sample F and the membrane filter. Thereafter, the sample F after drying is placed in a crucible together with a membrane filter, and is ignited and incinerated at 1300° C. or higher. The remaining residue is barium oxide. The mass of barium oxide is converted to the mass of barium sulfate to obtain the mass of barium sulfate (M _B ). The mass of the carbonaceous material is calculated by subtracting the mass M _B from the mass M _m .

<<Particle size of barium sulfate particles>>
A predetermined amount of sample F is placed in a crucible and heated at 500° C. in an oxygen atmosphere to convert the carbonaceous material into carbon dioxide and remove it. Barium sulfate is thus recovered as a residue. Using the recovered barium sulfate (sample G), the volume-based particle size distribution of the barium sulfate particles is measured with a laser diffraction particle size distribution analyzer. Mastersizer 3000 manufactured by Malvern Panalytical is used as a laser diffraction particle size distribution analyzer. The average particle size of the barium sulfate particles was obtained by adding sample G to an aqueous solution of sodium hexametaphosphate (NaHMP) (NaHMP concentration: 0.05% by mass) and performing ultrasonic dispersion for 1 minute. Measured using D10, D50 and D90 are determined from the resulting particle size distribution. From these values, the span value is determined using the above formula.

(Manufacturing method of negative electrode plate)
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 electrode plate, and then forming the unformed negative electrode plate. The negative electrode paste is prepared by adding water and sulfuric acid to lead powder, barium sulfate powder, an organic anti-shrinking agent and, if necessary, various additives, and kneading the mixture. For example, when using barium sulfate powder obtained by removing barium sulfate particles with a large particle size and barium sulfate particles with a small particle size by classifying the barium sulfate powder as a raw material, the span value of the barium sulfate particles in the negative electrode material is can be made smaller. Moreover, when synthesizing barium sulfate powder, the particle size and particle size distribution of the powder may be adjusted by adjusting the reaction conditions. The negative electrode active material in the charged state is spongy lead, but the unformed negative electrode plate is usually produced using lead powder. In the aging step, the unformed negative electrode plate is preferably aged at a temperature and humidity higher than room temperature.

Formation can be performed by charging the electrode plate group including the unformed negative electrode plate while the electrode plate group is immersed in an electrolytic solution containing sulfuric acid in the battery case of the lead-acid battery. However, formation may be performed before assembly of the lead-acid battery or the electrode plate assembly. Formation produces spongy lead.

(Positive plate)
A paste-type positive plate is used as the positive plate. 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 material is a portion of the positive electrode plate excluding the positive current collector. In addition, members such as mats and pasting paper may be attached to the electrode plates. Such a member (also referred to as a sticking member) is included in the electrode plate because it is used integrally with the electrode plate. When the positive electrode plate includes the sticking member, the positive electrode material is the portion of the positive electrode plate excluding the positive current collector and the sticking member.

The positive electrode current collector included in the positive electrode plate 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. It is preferable to use a grid-like current collector as the positive electrode current collector because it facilitates carrying the positive electrode material.

Pb--Ca alloys and Pb--Ca--Sn alloys are preferable as the lead alloy used for the positive electrode current collector in terms of corrosion resistance and mechanical strength. The positive electrode current collector may have lead alloy layers with different compositions, and the alloy layer may be a single layer or a plurality of layers.

The positive electrode material contained in the positive electrode plate 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 (such as reinforcing materials) as necessary.

Examples of reinforcing materials include fibers (inorganic fibers, organic fibers (such as organic fibers made of a resin described for the reinforcing material of the negative electrode material), etc.).

The content of the reinforcing material in the positive electrode material is, for example, 0.03% by mass or more. Moreover, the content of the reinforcing material in the positive electrode material is, for example, 0.5% by mass or less.

An unformed paste-type positive electrode plate is obtained by filling a positive electrode current collector with a positive electrode paste, followed by aging and drying. The positive electrode paste is prepared by adding water and sulfuric acid to lead powder, an antimony compound, and optionally other additives (reinforcing material, etc.) and kneading them.

A positive electrode plate is obtained by chemically forming an unformed positive electrode plate. Formation can be performed by charging the electrode plate group including the unformed positive electrode plate while immersing the electrode plate group in an electrolytic solution containing sulfuric acid in the battery case of the lead-acid battery. However, formation may be performed before assembly of the lead-acid battery or the electrode plate assembly.

(Electrolyte)
The electrolyte is an aqueous solution containing sulfuric acid. The electrolytic solution may be gelled if necessary.

The electrolytic solution may further contain at least one metal ion selected from the group consisting of Na ions, Li ions, Mg ions, and Al ions.

The specific gravity of the electrolytic solution at 20° C. is, for example, 1.10 or more. The specific gravity of the electrolytic solution at 20° C. may be 1.35 or less. It should be noted that these specific gravities are values for the electrolytic solution of a lead-acid battery in a fully charged state.

The matters described in this specification can be combined arbitrarily.

A method for evaluating the IS life performance will be described below.
Based on SBA S 0101:2014, the IS life test is performed in the following procedure.
a) Place the accumulator in the gas phase at 25±2° C. throughout the entire test period. The wind velocity in the vicinity of the storage battery shall be 2.0 m/s or less.
b) Connect the storage battery to the life test equipment and perform the following discharges (Discharge 1 and Discharge 2) and charge. This discharge and charge is one cycle of discharge and charge. The cycle of discharge and charge is then repeated continuously.
Discharge: Discharge 1 Discharge current I _D ± 1 A for 59.0 ± 0.2 seconds (where I _D is calculated using the following conversion formula and rounded to the first decimal place. I _D = 18 .3 x _I20 )
Discharge 2 Discharge current 300±1A for 1.0±0.2 seconds Charge: Charge voltage 14.00±0.03V (limit current 100.0±0.5A) for 60.0±0.3 seconds Cycle 3600 After 40-48 hours of rest each time, the cycle is started again. Water retention does not occur until 30,000 cycles.
The final discharge voltage (terminal voltage) of discharge 2 is measured, and the number of cycles until it reaches 7.2 V is obtained, which is used as an index of IS life performance.

FIG. 1 shows the appearance of an example of a lead-acid battery according to an embodiment of the present invention.
A lead-acid battery 1 includes a battery case 12 that accommodates an electrode plate group 11 and an electrolytic solution (not shown). The interior of the container 12 is partitioned into a plurality of cell chambers 14 by partition walls 13 . Each cell chamber 14 accommodates one electrode plate group 11 . The opening of the container 12 is closed with a lid 15 having a negative terminal 16 and a positive terminal 17 . The lid 15 is provided with a liquid port plug 18 for each cell chamber. When rehydrating, the rehydration liquid is replenished by removing the liquid port plug 18. - 特許庁The liquid port plug 18 may have a function of discharging the gas generated inside the cell chamber 14 to the outside of the battery.

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 bag-shaped separator 4 for housing the negative electrode plate 2 is shown, but the shape of the separator is not particularly limited. In a cell chamber 14 located at one end of the battery case 12, a negative electrode shelf portion 6 connecting a plurality of negative electrode plates 2 in parallel is connected to a through connector 8, and a positive electrode shelf portion connecting a plurality of positive electrode plates 3 in parallel. 5 is connected to the positive pole 7 . The positive pole 7 is connected to a positive terminal 17 outside the lid 15 . In the cell chamber 14 located at the other end of the battery case 12 , the negative electrode column 9 is connected to the negative electrode shelf 6 , and the through connector 8 is connected to the positive electrode shelf 5 . The negative electrode column 9 is connected to a negative electrode terminal 16 outside the lid 15 . Each through-connector 8 passes through a through-hole provided in the partition wall 13 and connects the electrode plate groups 11 of adjacent cell chambers 14 in series.

[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-acid batteries E1 to E14 and C1 to C15>>
Each lead-acid battery was produced in the following procedure.
(1) Preparation of Separator A resin composition containing 100 parts by mass of polyethylene, about 160 parts by mass of silica particles, about 80 parts by mass of paraffinic oil as a pore-forming agent, and 2 parts by mass of a penetrating agent was prepared into a sheet. A microporous membrane having ribs on one side was produced by extruding the membrane into a single layer, stretching the membrane, and removing part of the pore-forming agent. At this time, the cooling rate of the extruded sheet and the stretching ratio were adjusted so that the crystallinity of the separator obtained by the above-described procedure was the value shown in Table 1. In addition, the amounts of silica particles and pore-forming agent relative to polyethylene are adjusted so that the first pore volume Vt and oil content obtained by the above-described procedure are the values shown in Table 1, and the pore-forming agent is removed. adjusted the amount.

The content of silica particles determined by the procedure described above was about 60% by mass. The rib height determined by the procedure described above was 0.6 mm. The thickness of the separator (thickness of the base portion) determined by the above procedure was 0.2 mm.

Next, the sheet-like microporous membrane was folded in two so that ribs were arranged on the outer surface to form a bag, and the overlapped ends were crimped to obtain a bag-like separator.

The crystallinity of the separator, the first pore volume Vt, the oil content, the silica particle content, the thickness of the base portion, and the height of the rib are the values obtained for the separator before manufacturing the lead-acid battery. However, it is almost the same as the value measured by the above-described procedure for the separator taken out from the lead-acid battery after production.

(2) Production of positive electrode plate A positive electrode paste was prepared by mixing lead oxide, reinforcing material (synthetic resin fiber), water and sulfuric acid. The positive electrode paste was filled in the mesh part of an expanded lattice made of a Pb-Ca-Sn alloy containing no antimony, and then aged and dried to obtain an unformed unformed grid with a width of 100 mm, a height of 115 mm, and a thickness of 1.6 mm. A positive plate was obtained.

(3) Preparation of Negative Electrode Plate A negative electrode paste was prepared by mixing lead oxide, carbon black, barium sulfate powder, lignin, reinforcing material (synthetic resin fiber), water and sulfuric acid. As the barium sulfate powder, a powder having an average particle diameter D50 of 0.6 μm and having particles with a small particle diameter and particles with a large particle diameter removed by classification was used as necessary. The span value was adjusted by adjusting the particle size of the particles to be removed.

The negative electrode paste was filled in the mesh part of the expanded lattice made of Pb--Ca--Sn alloy, aged and dried to obtain an unformed negative electrode plate (width 100 mm, height 115 mm, thickness 1.2 mm). The amounts of carbon black, lignin, and synthetic resin fiber were adjusted to be 0.3% by mass, 0.1% by mass, and 0.1% by mass, respectively, when measured in the fully charged state of the chemically formed battery. The amount of the dispersion liquid added was adjusted so that the amount of barium sulfate was 2.1 parts by mass with respect to 100 parts by mass of the powder containing lead oxide as the main component.

(4) Preparation of lead-acid battery An unchemically formed negative electrode plate was placed in a bag-like separator and laminated with a positive electrode plate to form an electrode plate group with seven unchemically formed negative electrode plates and six unchemically formed positive electrode plates. .

Ears of the positive electrode plate and ears of the negative electrode plate were welded to the positive shelf and the negative shelf by a cast-on-strap method, respectively. The electrode plate group is inserted into a polypropylene battery case, the electrolyte is injected, and chemical conversion is performed in the battery case so that the rated voltage is 12 V and the rated capacity is 30 Ah (5 hour rate capacity (Ah described in the rated capacity). A liquid lead-acid battery with a capacity when discharged at a current (A) that is 1/5 of the value of )) was assembled. Six electrode plate groups are connected in series in the container.

An aqueous sulfuric acid solution was used as the electrolytic solution. The specific gravity at 20° C. of the electrolytic solution after chemical conversion was 1.285.

(5) Evaluation FIG. 2 shows the XRD spectrum of the separator of the lead-acid battery E1 measured by the procedure described above. As shown in FIG. 2, a diffraction peak corresponding to the (110) plane of the crystalline region of polyethylene was observed in the range of 2θ = 21.5° to 22.5°, and the diffraction peak corresponding to the (200) plane was observed. A peak was observed in the range 2θ=23° to 24.5°. A broad halo due to the amorphous region was observed over a wide range of 2θ=17° to 27°.

Using the obtained lead-acid battery, the IS life performance was evaluated by the procedure described above, and the span value of the barium sulfate particles in the negative electrode material was measured by the procedure described above. The IS life performance was evaluated by the ratio (%) of the number of cycles of each lead-acid battery when the number of cycles of the lead-acid battery C7 was taken as 100 (%).

Table 1 shows the evaluation results of the IS life performance. E1 to E14 in the table are examples. C1 to C15 are comparative examples.

As shown in Table 1, when the crystallinity of the separator was less than 20%, the IS life performance was generally low even when the first pore volume Vt changed, and the IS life performance became lower as the Vt increased.

On the other hand, when the crystallinity of the separator was 20% or more and Vt was 0.8 cm ³ /g or more, high IS life performance was obtained even when the span value of the barium sulfate particles was large. It can be seen that when the span value is 2.78 or less, high IS life performance can be secured, and the smaller the span value, the higher the IS life performance tends to be. Also, it can be seen that there is a tendency that the higher the crystallinity of the separator, the higher the IS life performance.

The lead-acid battery according to the above aspect of the present invention is suitable, for example, for IS applications (lead-acid batteries for idling stop system vehicles, etc.), starting power supplies for various vehicles (automobiles, motorcycles, etc.). In addition, the lead-acid battery can be suitably used as a power source for industrial power storage devices such as electric vehicles (forklifts, etc.). It should be noted that these uses are merely exemplary. Applications of the lead-acid battery according to the above aspects of the present invention are not limited to these.

1: lead-acid battery 2: negative electrode plate 3: positive electrode plate 4: separator 5: positive electrode shelf 6: negative electrode shelf 7: positive electrode column 8: through connector 9: negative electrode column 11: electrode plate group 12: battery case 13: partition wall 14: Cell chamber 15: Lid 16: Negative electrode terminal 17: Positive electrode terminal 18: Liquid port plug

Claims (8)

A lead-acid battery,
The lead-acid battery includes at least one cell including an electrode group and an electrolyte,
The electrode plate group includes a positive electrode plate, a negative electrode plate, and a separator interposed between the positive electrode plate and the negative electrode plate,
The negative plate comprises a negative electrode material containing barium sulfate particles,
In the volume-based particle size distribution of the barium sulfate particles, when the particle diameters at which the cumulative frequency is 10%, 50%, and 90% are D10, D50, and D90, respectively, (D90-D10)/D50 span value is 2.78 or less,
the separator includes a crystalline region and an amorphous region;
In the X-ray diffraction spectrum of the separator, the crystallinity indicated by 100×I _c /(I _c +I _a ) is 20% or more,
I _c is the integrated intensity of the diffraction peak having the maximum peak height among the diffraction peaks corresponding to the crystalline region;
I _a is the integrated intensity of the halo corresponding to the amorphous region;
The lead-acid battery, wherein the total volume Vt of pores having a pore diameter of 0.005 μm or more and 10 μm or less in the separator is 0.8 cm ³ /g or more. 2. The lead-acid battery according to claim 1, wherein said span value is 2.75 or less. The lead-acid battery according to claim 1 or 2, wherein the total volume Vt is 0.90 cm ³ /g or more. The lead-acid battery according to any one of claims 1 to 3, wherein said crystallinity is 40% or less. The lead-acid battery according to any one of claims 1 to 4, wherein the separator contains polyolefin. The polyolefin contains at least ethylene units,
6. The lead-acid battery of claim 5, wherein the diffraction peak with the highest peak height corresponds to the (110) plane due to the crystalline region. The lead-acid battery according to any one of claims 1 to 6, wherein said separator has a thickness of 100 µm or more and 300 µm or less. The lead-acid battery according to any one of claims 1 to 7, wherein the separator contains oil.

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