JP7643273B2 - Separator for lead-acid battery and lead-acid battery including same - Google Patents

Description

The present invention relates to a separator for a lead-acid battery and a lead-acid battery including the same.

Lead-acid batteries are used in vehicles, industrial applications, and a variety of other applications. Lead-acid batteries contain positive and negative electrode plates, a separator between them, and an electrolyte. Separators for lead-acid batteries are required to have a variety of performance characteristics. Porous films made of polyolefin are generally used as separators.

Patent document 1 proposes a separator for a lead acid battery comprising a polyolefin microporous membrane, the polyolefin microporous membrane comprising polyethylene, preferably ultra-high molecular weight polyethylene, a particulate filler, and a treatment plasticizer, the particulate filler being present in an amount of 40% or more by weight, the polyethylene comprising a shish-kebab-formed polymer comprising a plurality of extended chain crystals (shish formation) and a plurality of folded chain crystals (kebab formation), the average repetition or period of the kebab formation being 1 nm to 150 nm, preferably less than 120 nm.

In some cases, a porous film and a glass mat are used together as a separator. For example, Patent Document 2 proposes a lead-acid battery having a positive electrode plate, a negative electrode plate, an electrolyte, and a separator, the separator being made of a porous sheet and a glass mat, and the electrolyte containing aluminum ions at 0.02 mol/L or more and 0.2 mol/L or less, and lithium ions at 0.02 mol/L or more and 0.2 mol/L or less.

Patent Document 3 proposes a lead-acid battery in which a separator made of a porous resin thin film and a glass mat is interposed between positive and negative plates, and a group of electrodes in which these are alternately stacked is housed in a battery case, characterized in that (a) at least one side of the base part of the synthetic resin thin film is provided with a plurality of rib parts, (b) glass mats are attached between each of the rib parts, (c) glass mats are also attached to the outside of the rib parts at both ends, and further, (d) when the glass mat is attached to the base part of the synthetic resin thin film, the surface of the glass mat on the opposite side to the attached surface has a thickness that is higher than the top surface of the rib parts, and (e) when the separator with the glass mat attached to the synthetic resin thin film is inserted into the group of electrodes and housed in the battery case of the lead-acid battery, the glass mat is compressed under pressure until the rib parts come into contact with the positive plates, and the stacking pressure is 10 to 60 kPa.

Special table 2019-514173 publication JP 2013-84362 A JP 2016-139455 A

In lead-acid batteries, the positive electrode material softens when the battery is repeatedly charged and discharged. As in Patent Document 2 or 3, the provision of a glass fiber mat is advantageous in reducing the shedding of the softened positive electrode material. However, in a separator that is a laminate, the resistance is higher than in the case of only a porous film, and the cold cranking ampere (CCA) performance is reduced. The reduction in the thickness of the porous film can reduce the reduction in the CCA performance. However, since the thickness of the glass fiber mat is not so large, the fallen positive electrode material or the end of the current collector is likely to penetrate the glass fiber mat. If the thickness of the porous film that constitutes the laminate is small, the porous film breaks and shorts out, and the life performance in the heavy load life test is reduced. Therefore, it is difficult to ensure excellent life performance in the heavy load life test while ensuring high CCA performance. Hereinafter, the life performance in a heavy load cycle such as a heavy load life test may be simply referred to as the heavy load life performance.

One aspect of the present disclosure is a separator for a lead-acid battery,
The separator includes a laminate of a porous resin film and a glass fiber mat,
The porous film includes a crystalline region and an amorphous region,
In the X-ray diffraction spectrum of the porous film, the ratio R represented by A ₁ /(A ₁ +A ₂ ) is 0.60 or more;
_A1 is the area of the first diffraction peak having the maximum peak height among the diffraction peaks corresponding to the crystalline region,
_A2 relates to a separator for a lead-acid battery, in which the area of a second diffraction peak having the second highest peak height among the diffraction peaks corresponding to the crystalline region is the area of a second diffraction peak.

In lead-acid batteries, it is possible to ensure excellent heavy-load life performance while maintaining high CCA performance.

1 is a partially cutaway perspective view showing the appearance and internal structure of a lead-acid battery according to one embodiment of the present invention; FIG. 2 is a schematic plan view of the separator of FIG. 1 . 1 is an X-ray diffraction spectrum of a porous film used in a separator of the lead-acid battery E7 of an example.

A lead-acid battery separator according to one aspect of the present invention includes a laminate of a resin porous film and a glass fiber mat. The porous film includes a crystalline region and an amorphous region. In an X-ray diffraction (XRD) spectrum of the porous film, a ratio R represented by A ₁ /(A ₁ +A ₂ ) is 0.60 or more. Here, A ₁ is the area of a diffraction peak (first diffraction peak) having the maximum peak height among the diffraction peaks corresponding to the crystalline region. _{A 2} is the area of a diffraction peak (second diffraction peak) having the second highest peak height among the diffraction peaks corresponding to the crystalline region.

The ratio R indicates the degree of crystallinity of the porous film. In the porous film used in the conventional separator, the ratio R tends to be relatively low, for example, approximately 0.58 or less. In contrast, in the separator of the above side, the ratio R of the porous film is 0.60 or more, and a porous film with higher crystallinity than the conventional one is used. By increasing the crystallinity of the porous film constituting the separator, the strength of the porous film itself (specifically, piercing strength) can be improved. Therefore, even if the end of the fallen positive electrode material or the current collector penetrates the glass fiber mat and contacts the porous film, it is possible to suppress the occurrence of a short circuit due to the penetration of the porous film or the breakage of the porous film due to oxidative deterioration. This can improve the life performance in the heavy load life test, which is a condition under which the positive electrode material is likely to fall off. By making the ratio R of the porous film 0.60 or more, a certain degree of strength can be secured even if the thickness of the porous film is reduced. Since high heavy load life performance can be obtained even if the thickness of the porous film is reduced, the deterioration of CCA performance can be suppressed. In this way, it is possible to ensure high CCA performance while also ensuring excellent heavy load life performance.

In this specification, heavy load life performance refers to the life performance when a cycle of discharge and charge is repeated in a region (also called the heavy load region) where the depth of discharge in one cycle is 20% or more, assuming the rated capacity (5-hour rate capacity) to be 100%. Such a cycle of discharge and charge is sometimes called a heavy load cycle.

The porous film itself may also be used as a separator for a lead-acid battery. Unlike separators for lithium-ion secondary batteries, etc., a porous film separator for a lead-acid battery has a certain degree of thickness. In addition, the thicker the porous film, the more difficult it tends to be to increase the crystallinity. In addition, as the crystallinity increases, the porous film tends to become hard and brittle. From this perspective, the crystallinity has not been controlled in conventional porous films used in separators for lead-acid batteries. In contrast to this conventional wisdom, in one aspect of the lead-acid battery separator of the present invention, the ratio R of the porous film laminated to the glass fiber mat is set to 0.60 or more, so that the resistance of the porous film can be kept low while high strength can be ensured, and an increase in the resistance of the laminate with the glass fiber mat can be suppressed.

The thickness of the porous film is preferably 100 μm or more. When the thickness is in this range, it is easy to ensure higher strength and higher heavy load life performance. The thickness of the porous film is preferably 300 μm or less. In this case, it is easy to keep the resistance of the porous film low, so it is easy to obtain relatively high CCA performance.

It is preferable that the ratio R is 0.9 or less. In this case, it is easy to ensure the flexibility of the porous film while suppressing deterioration of the porous film, and it is also easy to manufacture.

The porous film preferably contains a polyolefin, and more preferably contains a polyolefin containing at least ethylene units. Such porous films tend to have relatively low strength, but the ratio R is relatively easy to adjust, and the strength of the separator can be increased by adjusting the ratio R. When the porous film contains a polyolefin containing at least ethylene units, the first diffraction peak corresponds to the (110) plane due to the crystalline region, and the second diffraction peak corresponds to the (200) plane due to the crystalline region.

The porous film may have an area at least partially at the end that is not covered with the glass fiber mat. In such an area, the fallen positive electrode material may pierce the porous film or come into contact with the porous film and cause oxidative deterioration, which may cause a short circuit and reduce the life performance in a heavy load life test. However, even in such a case, the high ratio R of the porous film can improve the strength of the porous film itself, thereby reducing the occurrence of short circuits.

The present invention also includes a lead-acid battery including the above-mentioned separator for lead-acid batteries. The lead-acid battery includes at least one cell including an electrode plate group and an electrolyte, and the electrode plate group includes a positive electrode plate, a negative electrode plate, and the above-mentioned separator interposed between the positive electrode plate and the negative electrode plate. Here, the glass fiber mat of the separator is in contact with the positive electrode plate. By using the above-mentioned separator, the resistance of the separator can be kept low, and high CCA performance can be ensured. By obtaining high strength of the porous film, tearing of the porous film due to the fallen positive electrode material or the end of the current collector is suppressed, and the occurrence of short circuits is suppressed, so that excellent heavy load life performance can be ensured.

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

In this specification, the up-down direction of a lead-acid battery or components of a lead-acid battery (electrode plates, battery case, separator, etc.) refers to the up-down direction in the vertical direction of the lead-acid battery when the lead-acid battery is in use. Each of the positive and negative electrode plates has a lug for connecting to an external terminal, and in a liquid battery, the lug is provided on the top of the electrode plate so as to protrude upward.

Below, the separator and lead-acid battery according to the embodiment of the present invention will be described in more detail with reference to the drawings. However, the present invention is not limited to the following embodiment.

(Separator)
The separator includes a laminate of a porous resin film and a glass fiber mat.

(Porous film)
The porous film includes a crystalline region in which the molecules of the constituent material (specifically, the resin material) of the porous film are arranged relatively regularly (i.e., highly ordered), and an amorphous region in which the molecules are arranged less ordered. Therefore, in the XRD spectrum of the porous film, a diffraction peak due to the crystalline region is observed, and scattered light due to the amorphous region is observed as a halo. In the XRD spectrum of the porous film, the ratio R represented by _A1 /( _A1 + _A2 ) is 0.60 or more, so that the porous film has high strength. Here, _A1 is the area of the diffraction peak (first diffraction peak) with the maximum peak height among the diffraction peaks corresponding to the crystalline region, and _A2 is the area of the diffraction peak (second diffraction peak) with the second highest peak height among the diffraction peaks corresponding to the crystalline region.

For example, in the XRD spectrum of a porous film 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°, and a diffraction peak corresponding to the (200) plane of the crystalline region is observed in the range of 2θ from 23° to 24.5°. A halo of the amorphous region is observed in the range of 2θ from 17° to 27°. Of the diffraction peaks due to the crystalline region, the diffraction peak corresponding to the (110) plane has the largest peak height and corresponds to the first diffraction peak. The diffraction peak corresponding to the (200) plane has the second highest peak height and corresponds to the second diffraction peak.

The ratio R is 0.60 or more, and from the viewpoint of ensuring a higher strength of the porous film, it may be 0.65 or more, 0.70 or more, or 0.75 or more. The ratio R may be 0.9 or less, 0.85 or less, or 0.80 or less. When the ratio R is in such a range, it is easy to ensure the flexibility of the separator, and it is easy to manufacture.

The ratio R is 0.60 or more (or 0.65 or more) and 0.9 or less, 0.60 or more (or 0.65 or more) and 0.85 or less, 0.60 or more (or 0.65 or more) and 0.80 or less,
It may be 0.70 or more (or 0.75 or more) and 0.9 or less, 0.70 or more (or 0.75 or more) and 0.85 or less, or 0.70 or more (or 0.75 or more) and 0.80 or less.

The areas of the diffraction peaks are obtained by fitting the diffraction peaks due to the crystalline regions in the XRD spectrum of the porous film. The ratio R is calculated from the above formula using the area _A1 of the first diffraction peak and the area _A2 of the second diffraction peak.

The porous film includes, for example, a polymer material (hereinafter also referred to as a base polymer). Since the porous film includes crystalline regions, the base polymer typically includes a crystalline polymer. The porous film includes, for example, a polyolefin. A polyolefin is a polymer that includes at least olefin units (i.e., a polymer that includes at least monomer units derived from an olefin).

As the base polymer, polyolefin may be used in combination with other base polymers. The ratio of polyolefin to the total base polymer contained in the porous film is, for example, 50% by mass or more, 80% by mass or more, or 90% by mass or more. The ratio of polyolefin is, for example, 100% by mass or less. The base polymer may be composed of polyolefin only. When the ratio of polyolefin is this high, the strength of the porous film tends to be low, but even in such a case, high strength can be ensured because the ratio R is in the above range.

Polyolefins include, for example, homopolymers of olefins, copolymers containing different olefin units, and copolymers containing olefin units and copolymerizable monomer units. A copolymer containing olefin units and copolymerizable monomer units may contain one or more types of olefin units. A copolymer containing olefin units and copolymerizable monomer units may contain one or more types of 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.

The polyolefin may be, for example, a polymer containing at least a C _2-3 olefin as a monomer unit. The C _2-3 olefin may be at least one selected from the group consisting of ethylene and propylene. The polyolefin may be, for example, polyethylene, polypropylene, or a copolymer containing a C _2-3 olefin as a monomer unit (for example, an ethylene-propylene copolymer). Among the polyolefins, it is preferable to use a polyolefin containing at least an ethylene unit (polyethylene, ethylene-propylene copolymer, etc.). A polyolefin containing an ethylene unit (polyethylene, ethylene-propylene copolymer, etc.) may be used in combination with another polyolefin.

It is preferable that the porous film contains oil. When the porous film contains oil, the effect of suppressing oxidative deterioration of the porous film is enhanced. Even if the porous film comes into contact with fallen positive electrode material, the oxidative deterioration of the porous film is suppressed, so the occurrence of tearing can be further reduced.

Oil refers to a hydrophobic substance that is liquid at room temperature (a temperature between 20°C and 35°C) and separates from water. Oil includes naturally occurring oils, mineral oils, and synthetic oils. Mineral oils and synthetic oils are preferred as oils. Examples of oils include paraffin oil and silicone oil. The porous film may contain one type of oil or a combination of two or more types of oil.

The oil content in the porous film is preferably 11% by mass or more and 18% by mass or less. When the oil content is in this range, the effect of suppressing oxidative deterioration of the porous film is further enhanced. In addition, the resistance of the separator can be kept relatively low.

The porous film may be in a sheet shape. A sheet-shaped porous film may be folded into an accordion shape and used as a separator. The porous film may be formed in a bag shape. Either the positive electrode plate or the negative electrode plate may be housed in the bag-shaped porous film.

The porous film may or may not have ribs. A porous film with ribs, for example, comprises a base portion and ribs erected from the surface of the base portion. The ribs may be provided on only one surface of the porous film or each of the base portions, or on both surfaces. The base portion of the porous film refers to the constituent parts of the porous film excluding protrusions such as ribs, and refers to the sheet-like portion that defines the outer shape of the porous film.

The thickness of the porous film is, for example, 90 μm or more. From the viewpoint of obtaining higher strength, 100 μm or more is preferable. The thickness of the porous film is, for example, 300 μm or less, and may be 250 μm or less. From the viewpoint of keeping the resistance of the porous film low and easily ensuring higher CCA performance, the thickness of the porous film is preferably 200 μm or less, and may be 150 μm or less. Even if the thickness of the porous film is so small, sufficient strength can be obtained and high heavy load life performance can be ensured. The thickness of the porous film means the average thickness of the part of the porous film facing the electrode material. When the porous film has a base portion and a rib erected from at least one surface of the base portion, the thickness of the porous film is the average thickness of the base portion.

The thickness of the porous film may be 90 μm or more (or 100 μm or more) and 300 μm or less, 90 μm or more (or 100 μm or more) and 250 μm or less, 90 μm or more (or 100 μm or more) and 200 μm or less, or 90 μm or more (or 100 μm or more) and 150 μm or less.

When the porous film has ribs, the height of the ribs may be 50 μm or more. Also, the height of the ribs may be 1.2 mm or less. The height of the ribs is the height of the part that protrudes from the surface of the base part (protrusion height).

In the above aspect of the present invention, the ribs of the porous film may be provided on the surface on the negative electrode plate side. In this case, the ribs are preferably provided on the portion of the porous film facing the negative electrode material. By providing the ribs on the negative electrode plate side, the electrolyte can be easily diffused. The height of the ribs provided on the negative electrode plate side is, for example, 50 μm or more. The height of the ribs may be, for example, 400 μm or less or 300 μm or less.

When ribs are provided on the positive electrode plate side of the porous film, they may be provided in an area that is not covered with the glass fiber mat. When ribs are provided in a portion facing the positive electrode material, the glass fiber mat may be disposed between adjacent ribs, as in Patent Document 2. However, in consideration of the ease of lamination with the glass fiber mat, it is not necessary to provide ribs on the positive electrode plate side of the porous film.

The porous film may have an area not covered with the glass fiber mat at least in a part of the end. If the fallen positive electrode material comes into contact with this area, the porous film may be oxidized and deteriorated, or the positive electrode material may be embedded in the porous film, causing the porous film to break, resulting in a short circuit and shortening the life of the porous film. However, in the above aspect of the present invention, even in such a case, the strength of the porous film is increased, thereby suppressing the breakage of the porous film and suppressing the occurrence of a short circuit. The porous film is approximately rectangular, and usually has a total of four ends, including the upper and lower ends and both side ends. At one end, the width of the area of the porous film not covered with the glass fiber mat (for example, w _p in FIG. 2 described later) may be, for example, 1 mm or more, and may be 2 mm or more. The width of this area may be, for example, 5 mm or less, 4.5 mm or less, or 4 mm or less. The porous film may have an area not covered with the glass fiber mat at the side end (preferably both side ends). When the bag-shaped porous film and the glass fiber mat are laminated together, a predetermined area of the side edge including the portion compressed into a bag shape is exposed outside the glass fiber mat.

The width of the above region may be 1 mm or more (or 2 mm or more) and 5 mm or less, 1 mm or more (or 2 mm or more) and 4.5 mm or less, or 1 mm or more (or 2 mm or more) and 4 mm or less.

The porous film can be obtained, for example, by extruding a resin composition containing a base polymer, a pore-forming agent, and a penetrating agent (surfactant) into a sheet, stretching the resin composition, and then removing at least a portion of the pore-forming agent. By removing at least a portion of the pore-forming agent, fine pores are formed in the matrix of the base polymer. After removing the pore-forming agent, the sheet-shaped porous film is dried as necessary. For example, the ratio R is adjusted by adjusting at least one selected from the group consisting of the cooling rate of the sheet during extrusion molding, the stretching ratio during stretching, and the temperature during drying. For example, the ratio R tends to be higher when the sheet is rapidly cooled during extrusion molding, the stretching ratio is increased, or the temperature during drying is decreased. The stretching process may be performed by biaxial stretching, but is usually performed by uniaxial stretching. The sheet-shaped porous film may be folded into a bellows shape or processed into a bag shape as necessary.

In a porous film having ribs, the ribs may be formed on the sheet when the resin composition is extruded. Alternatively, the ribs may be formed by pressing the sheet with a roller having grooves corresponding to each rib after the resin composition is molded into a sheet or after the pore-forming agent is removed.

Examples of the pore-forming agent include liquid pore-forming agents and solid pore-forming agents. The pore-forming agent preferably contains at least oil. By using oil, a porous film containing oil can be obtained, and the effect of suppressing oxidative deterioration can be enhanced. The pore-forming agent may be used alone or in combination of two or more types. Oil may be used in combination with another pore-forming agent. A liquid pore-forming agent may be used in combination with a solid pore-forming agent. At room temperature (a temperature of 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 is classified as a solid pore-forming agent.

As a liquid pore-forming agent, the above-mentioned oil is preferable. As a solid pore-forming agent, for example, a polymer powder can be mentioned.

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

For example, a porous film containing oil is formed by extracting and removing some of the oil from a sheet formed using oil as a pore-forming agent using a solvent. The solvent is selected, for example, depending on the type of oil. For example, the oil content in the porous film can be adjusted by adjusting the type and composition of the solvent, the extraction conditions (extraction time, extraction temperature, rate at which the solvent is supplied, etc.), etc.

The surfactant used as the penetrating agent may be, for example, either an ionic surfactant or a nonionic surfactant. The surfactant may be used alone or in combination of two or more kinds.

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

The porous film (or the resin composition used to produce the porous film) may contain inorganic particles.

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

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

(fiberglass mat)
The glass fiber mat is laminated on the surface of the porous film facing the positive electrode plate. For example, in the case of a bag-shaped porous film, the glass fiber mat may be laminated on both outer surfaces of the bag. For example, when the electrode plate at the end of the electrode plate group is a negative electrode plate, the bag-shaped porous film that houses the negative electrode plate may have the glass fiber mat laminated on the surface facing the positive electrode plate, and the surface not facing the positive electrode plate may have the porous film exposed.

A glass fiber mat is a mat (or nonwoven fabric) made of glass fibers. The glass fiber mat may be a material called absorbent glass mat (AGM).

The glass fiber mat may be entirely made of glass fibers. The glass fiber mat may contain glass fibers as a main component. The glass fiber content in the glass fiber mat may be 90% by mass or more, or 95% by mass or more. The glass fiber content in the glass fiber mat is 100% by mass or less. The glass fiber mat may contain components other than glass fibers, such as organic fibers, acid-resistant inorganic powders, and polymers as binders, but the content of these is usually 10% by mass or less, or 5% by mass or less.

The average fiber diameter of the glass fibers is, for example, 0.1 μm or more, and may be 0.5 μm or more. When the average fiber diameter of the glass fibers is in this range, the effect of suppressing the falling off of the softened positive electrode material is enhanced. The average fiber diameter of the glass fibers is, for example, 30 μm or less, and may be 10 μm or less. In this case, an excessive increase in the internal resistance of the battery can be suppressed. In addition, the glass fiber mat can ensure a relatively high flexibility and easily retain a relatively large amount of electrolyte.

The average fiber diameter of the glass fibers may be 0.1 μm or more (or 0.5 μm or more) and 30 μm or less, or 0.1 μm or more (or 0.5 μm or more) and 10 μm or less.

The surface density of the glass fiber mat is, for example, 100 g/m ² or more. The surface density of the glass fiber mat may be 250 g/m ² or less, or may be 200 g/m ² or less.

The separator can be obtained, for example, by laminating a porous film and a glass fiber mat. More specifically, the separator can be formed by laminating a glass fiber mat on the surface of the porous film facing the positive electrode plate. The porous film and the glass fiber mat can be simply stacked, or can be laminated (or fixed) using an adhesive. The porous film and the glass fiber mat can also be laminated (or fixed) using welding (heat sealing, etc.) or mechanical bonding methods (gear sealing, etc.). Examples of adhesives include silicone adhesives, epoxy adhesives, and polyolefin adhesives. It is preferable to apply a small amount of adhesive so that the resistance of the separator does not increase. For example, it is preferable to apply the adhesive partially rather than to the entire surface of the porous film or glass fiber mat to be bonded.

(Analysis or size measurement of porous films and fiberglass mats)
(Preparation of separator)
For the analysis or size measurement of the porous film or glass fiber mat, a separator that has not been used or that has been removed from a lead-acid battery in a fully charged state is used. The separator removed from the lead-acid battery is washed and dried prior to the analysis or measurement.

The separator removed from the lead-acid battery is washed and dried according to the following procedure. The separator removed from the lead-acid battery is immersed in pure water for one hour to remove the sulfuric acid from the separator. The separator is then removed from the liquid and left to stand for at least 16 hours in an environment of 25°C ± 5°C until it is dried.

In this specification, the fully charged state of a liquid-type lead-acid battery is defined by the definition of JIS D 5301:2019. More specifically, the fully charged state is a state in which a lead-acid battery is charged in a water tank at 25°C ± 2°C with a current (A) that is 1/10 of the value described as the rated capacity, until the terminal voltage (V) during charging measured every 15 minutes or the electrolyte density converted to a temperature of 20°C shows a constant value with three significant digits three times in a row. In addition, in the case of a valve-regulated lead-acid battery, the fully charged state is a state in which constant current and constant voltage charging is performed at 2.23 V/cell in an air tank at 25°C ± 2°C with a current (A) that is 0.2 times the value (unit: Ah) described as the rated capacity, and charging is terminated when the charging current during constant voltage charging becomes 0.005 times the value (unit: Ah) described as the rated capacity. The value described as the rated capacity is a value in Ah. The unit of current set based on the value listed as the rated capacity is A.

A fully charged lead-acid battery is a lead-acid battery that has already been chemically prepared and is fully charged. A lead-acid battery may be fully charged immediately after chemical preparation, or after a period of time has passed since chemical preparation (for example, a lead-acid battery that is in use (preferably in the early stages of use) after chemical preparation may be fully charged).

In this specification, a battery in its early stages of use is one that has not been in use for very long and has not deteriorated much.

(XRD spectrum)
The XRD spectrum of the porous film is measured by irradiating the surface of the porous film facing the positive electrode plate with X-rays perpendicularly. A sample for measurement is prepared by peeling the glass fiber mat from the porous film of the separator and processing the area where no adhesive is applied into a strip. For a porous film having ribs on the surface facing the positive electrode plate, the sample is processed so that it does not include the ribs. The measurement and fitting of the XRD spectrum are performed under the following conditions.
(Measurement conditions)
Measurement device: RINT-TTR2, manufactured by Rigaku Fitting: FT (step scan) method Measurement angle range: 15-35°
Step width: 0.02°
Measurement speed: 5°/min
XRD data processing: XRD pattern analysis software (PDXL2, manufactured by Rigaku) was used.

(Porous film thickness and rib height)
The thickness of the porous film is determined by measuring the thickness of the porous film portion at five arbitrarily selected points in a cross-sectional photograph of the separator and averaging the measured values.

The height of the rib is determined by averaging the heights of the base of the rib from one surface measured at 10 randomly selected points on the rib in a cross-sectional photograph of the separator.

(Oil content in porous film)
In the separator, the glass fiber mat is peeled off from the porous film. The area where the adhesive is not applied, which faces the electrode material of the separator, is processed into a rectangular shape to prepare a sample (hereinafter referred to as Sample A). In the case where the porous film has ribs, Sample A is processed so that it does not include the ribs.

Approximately 0.5 g of sample A is taken and accurately weighed to determine the initial mass (m0) of the sample. The weighed sample A is placed in a glass beaker of an appropriate size, and 50 mL of n-hexane is added. Next, ultrasonic waves are applied to the sample together with the beaker for about 30 minutes to dissolve the oil contained in sample A into n-hexane. Next, the sample is taken out of n-hexane, dried in the air at room temperature (temperature of 20°C or higher and 35°C or lower), and then weighed to determine the mass (m1) of the sample after removing the oil. Then, the oil content is calculated by the following formula. The oil content of 10 samples A is calculated and the average value is calculated. The obtained average value is taken as the oil content in the porous film.
Oil content (mass%)=(m0-m1)/m0×100

(Content of inorganic particles in porous film)
A portion of the sample A prepared in the same manner as above is taken, accurately weighed, and then placed in a platinum crucible and heated with a Bunsen burner until no white smoke is generated. The obtained sample is then heated in an electric furnace (in oxygen gas flow, 550°C ± 10°C) for about 1 hour to be incinerated, and the incinerated material is weighed. The ratio (percentage) of the mass of the incinerated material to the mass of sample A is calculated, and this is the content (mass%) of the inorganic particles. The content of the inorganic particles is determined for 10 samples A, and the average value is calculated. The obtained average value is the content of the inorganic particles in the porous film.

(Content of penetrant in porous film)
A part of sample A prepared in the same manner as above is taken, accurately weighed, and then dried for 12 hours or more at room temperature (temperature of 20°C to 35°C) in a reduced pressure environment lower than atmospheric pressure. The dried product is placed in a platinum cell and set in a thermogravimetric measuring device, and the temperature is raised from room temperature to 800°C ± 1°C at a heating rate of 10K/min. The weight loss amount 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 (mass%) of the penetrant is taken as the above. As the thermogravimetric measuring device, a Q5000IR manufactured by T. A. Instruments is used. The content of the penetrant is determined for 10 samples A, and the average value is calculated. The obtained average value is taken as the content of the penetrant in the porous film.

(Average fiber diameter of glass fiber mat)
The average fiber diameter of the glass fibers is determined by determining the maximum diameter of any 100 fibers taken out from the glass fiber mat portion of the separator in any cross section perpendicular to the length direction, and averaging the maximum diameter.

(Glass mat surface density)
The portion of the separator facing the electrode material is cut, and the portion not coated with adhesive is collected and weighed, and the length and width of the glass fiber mat portion (in other words, the length and width of the cut portion) are measured. The glass fiber mat is peeled off from the cut portion to measure the mass of the porous film. The mass of the glass fiber mat portion is calculated by subtracting the mass of the porous film from the mass of the cut portion. The area is calculated from the length and width of the glass fiber mat portion, and the mass (g) of the glass fiber mat portion per 1 ^m2 is calculated as the areal density.

(Positive electrode plate)
A paste-type positive electrode plate is used as the positive electrode plate. The paste-type positive electrode plate includes a positive electrode collector and a positive electrode material. The positive electrode material is held by the positive electrode collector. The positive electrode material is the portion of the positive electrode plate excluding the positive electrode collector. Note that a member such as a mat or pasting paper may be attached to the electrode plate. Such a member (also called an attachment member) is used integrally with the electrode plate, and is therefore included in the electrode plate. When the positive electrode plate includes an attachment member, the positive electrode material is the portion of the positive electrode plate excluding the positive electrode collector and the attachment member.

The positive electrode current collector included in the positive electrode plate may be formed by casting lead (Pb) or a lead alloy, or by processing a lead or lead alloy sheet. Examples of processing methods include expanding and punching. It is preferable to use a lattice-shaped current collector as the positive electrode current collector because it is easy to support the positive electrode material.

As the lead alloy used for the positive electrode current collector, a Pb-Ca alloy or a Pb-Ca-Sn alloy is preferred 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 multiple layers.

The positive electrode material contained in the positive plate contains 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, etc.). Examples of resins (or polymers) that make up the organic fibers include at least one selected from the group consisting of 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 positive electrode material is, for example, 0.03 mass% or more. Also, the content of the reinforcing material in the positive electrode material is, for example, 0.5 mass% or less.

Unformed paste-type positive plates are obtained by filling a positive electrode collector with a positive electrode paste, aging it, and drying it. The positive electrode paste is prepared by adding water and sulfuric acid to lead powder, an antimony compound, and other additives (such as reinforcing materials) as necessary, and kneading them.

A positive plate is obtained by chemically forming an unformed positive plate. Chemical formation can be performed by charging a plate group including an unformed positive plate while the plate group is immersed in an electrolyte containing sulfuric acid in a lead-acid battery container. However, chemical formation may also be performed before assembling the lead-acid battery or the plate group.

(Negative plate)
The 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 the portion of the negative electrode plate excluding the negative current collector. Note that an attachment member as described above may be attached to the negative electrode plate. In this case, the attachment member is included in the negative electrode plate. In the case where the negative electrode plate includes an attachment member, the negative electrode material is the portion of the negative electrode plate excluding the negative current collector and the attachment member.

The negative electrode current collector can be formed in the same manner as the positive electrode current collector.

The lead alloy used in the negative electrode current collector may be any of Pb-Sb alloys, Pb-Ca alloys, and Pb-Ca-Sn alloys. These lead or lead alloys may further contain at least one element 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 multiple layers.

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

Examples of organic shrinkage inhibitors include lignin, lignin sulfonic acid, and synthetic organic shrinkage inhibitors (such as formaldehyde condensates of phenolic compounds). The negative electrode material may contain one type of organic shrinkage inhibitor, or two or more types.

The content of the organic shrinkage inhibitor in the negative electrode material is, for example, 0.01% by mass or more. The content of the organic shrinkage inhibitor is, for example, 1% by mass or less.

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

The content of the carbonaceous material in the negative electrode material is, for example, 0.1 mass% or more. The content of the carbonaceous material may be, for example, 3 mass% or less.

The barium sulfate content in the negative electrode material is, for example, 0.1% by mass or more. The barium sulfate content is, for example, 3% by mass or less.

Examples of reinforcing materials include fibers (inorganic fibers, organic fibers (such as organic fibers made of resins as described for reinforcing materials for the positive electrode material)).

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

The negative electrode active material in the charged state is spongy lead, but unformed negative plates are usually made from lead powder.

The negative electrode plate can be formed by filling a negative electrode current collector with a negative electrode paste, maturing and drying it to produce an unformed negative electrode plate, and then chemically forming the unformed negative electrode plate. The negative electrode paste is made by adding water and sulfuric acid to lead powder, an organic shrinkage inhibitor, and various additives as necessary, and kneading them. In the maturation process, it is preferable to mature the unformed negative electrode plate at a temperature higher than room temperature and at high humidity.

The chemical formation can be carried out by immersing the plate group, including the unformed negative plate, in an electrolyte containing sulfuric acid in a lead-acid battery container and then charging the plate group. However, chemical formation can also be carried out before assembling the lead-acid battery or the plate group. Chemical formation produces spongy lead.

(Electrolyte)
The electrolyte is an aqueous solution containing sulfuric acid, and may be gelled as necessary.

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

The evaluation method for each characteristic is explained below.

(1) Puncture Strength The puncture strength of a separator (porous film) is measured by the following procedure.
In accordance with JIS Z 1707:2019, 7.5 "Puncture Strength Test", a test piece including the edge of the separator (more specifically, the edge of both side ends of the porous film exposed from the glass fiber mat of the separator) is fixed with a jig, the needle of the tester is pierced into the edge, and the maximum force (N) until the needle penetrates is measured. Five test pieces are measured in the same manner, and the average value is calculated and used as the piercing strength. The test piece is prepared by cutting the separator (the above-mentioned edge of the porous film) to a size of 50 mm long x 50 mm wide so as to include the edge. In the case where a crimped portion is formed on both side ends of the porous film in a bag-shaped porous film, the piercing strength is measured for the part other than the crimped portion of the edge. As a tester, AGS-X, 10N-10kN manufactured by Shimadzu Corporation is used. The needle used is a needle with a diameter of 1.0 mm and a semicircular tip (radius 0.5 mm), and the test speed is 50±5 mm/min. The jig used to fix the test piece is a jig with a diameter of 10 mm on the upper surface of the measurement part and a diameter of 20 mm on the lower side.

(2) CCA Performance In accordance with JIS D 5301:2019, the starting ability of a lead-acid battery is evaluated by the current value at which the terminal voltage 30 seconds after the start of discharge is 7.2 V or higher, using the following procedure. A higher current value indicates higher starting ability and lower separator resistance.
(a) After the battery is fully charged, place it in a cooling room at -18°C ± 1°C for at least 16 hours.
(b) After confirming that the electrolyte temperature in one of the central cells is -18°C ± 1°C, discharge it for 30 seconds at CCA390A.
(c) Record the terminal voltage 30 seconds after the start of discharge.

(3) Heavy Load Life Performance The heavy load life performance is evaluated as follows.
JIS D 5301:2019 9.5.5 Life Test b) A heavy load test is performed in accordance with the heavy load life test. More specifically, a fully charged lead-acid battery is first discharged for 1 hour at the discharge current shown in Table 1, and then charged for 5 hours at the charge current shown in Table 1. This cycle of discharge and charge is defined as one cycle. The discharge current and discharge current are changed as shown in Table 1 according to the 5-hour rate capacity of the lead-acid battery. The following explanation of the heavy load test is an example of using a lead-acid battery with a 5-hour rate capacity of 48 Ah. During the test, the lead-acid battery is placed in a water tank at 40°C ± 2°C. The water surface of the tank is positioned 15 mm to 25 mm below the top surface of the battery. When several lead-acid batteries are placed in the tank, the distance between adjacent lead-acid batteries and the distance between the lead-acid batteries and the inner wall of the adjacent tank are each set to at least 25 mm.

During the test, the battery is continuously discharged at a discharge current of 20A every 25 cycles until the terminal voltage of the lead-acid battery reaches 10.2V, and the discharge duration is recorded. Next, the battery is charged at a charging current of 5A every 15 minutes until the terminal voltage of the lead-acid battery or the specific gravity of the electrolyte (converted value at 25°C) indicates a constant value with three significant digits for three consecutive cycles. This discharge and charge are also counted towards the lifespan.

The test is terminated when it is confirmed that the capacity (Ah) calculated from the product of the discharge time and the discharge current measured in the above test falls to 50% or less of the rated capacity of 48 Ah and does not rise again. The number of times (life times) at which the capacity reaches 50% of the rated capacity of 48 Ah is used as an index of the life performance in heavy load cycles. The fact that the capacity does not rise again is confirmed by charging to a fully charged state after the capacity falls to 50% of the rated capacity, and discharging again in the same manner as above, and the capacity calculated from the product of the discharge time and the discharge current at this time is 50% or less of the rated capacity. The life times are calculated by approximating the number of cycles at 50% of the rated capacity from a graph of the number of cycles vs. capacity plotted with the discharge capacity every 25 cycles.
When the amount of electrolyte reaches the lower line (LL) of the lead-acid battery container, the number of cycles at this time is determined as the life due to electrolyte loss. If the container does not have an LL, the number of cycles when the electrolyte level drops to the top of the positive electrode strap (positive electrode shelf) is determined as the life due to electrolyte loss.

The items described in this specification may be combined in any manner.

FIG. 1 shows the external appearance of an example of a lead-acid battery according to an embodiment of the present invention.
The lead-acid battery 1 includes a battery case 12 that contains a plate group 11 and an electrolyte (not shown). The battery case 12 is divided into a plurality of cell chambers 14 by partitions 13. Each cell chamber 14 contains one of the plate groups 11. The opening of the battery case 12 is closed by a lid 15 that includes a negative electrode terminal 16 and a positive electrode terminal 17. The lid 15 is provided with a vent plug 18 for each cell chamber. When rehydrating, the vent plug 18 is removed and rehydration liquid is replenished. The vent plug 18 may have a function of discharging gas generated in the cell chamber 14 to the outside of the battery.

Each electrode plate group 11 is formed by stacking a plurality of negative electrode plates 2 and positive electrode plates 3 with separators 4 between them. In the cell chamber 14 located at one end of the battery case 12, the negative electrode shelf 6 that connects the plurality of negative electrode plates 2 in parallel is connected to the through connector 8, and the positive electrode shelf 5 that connects the plurality of positive electrode plates 3 in parallel is connected to the positive electrode column 7. The positive electrode column 7 is connected to a positive electrode 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 to connect the electrode plate groups 11 of adjacent cell chambers 14 in series.

FIG. 2 is a schematic plan view of the separator 4. The separator 4 is a laminate of a bag-shaped porous film 4a and a glass fiber mat 4b. The bag-shaped porous film 4a houses the negative electrode plate 2 of FIG. 1. The bag-shaped porous film 4a has a fold at the bottom end in FIG. 2 and an opening at the top end. At both side ends of the bag-shaped porous film 4a, a pressure-bonding portion 20 is provided linearly in the vertical direction so as to close the overlapped porous film 4a. At both side ends of the bag-shaped porous film 4a, a region 21 that is not covered with the glass fiber mat 4b is formed. The side end of the glass fiber mat 4b is located inside the pressure-bonding portion 20. Therefore, the width w _p of the region 21 is larger than the width w a from the side end of the porous film 4a to the pressure-bonding portion 20 (more specifically, the outer position of the pressure-bonding portion ₂₀ ).

In the lead-acid battery 1, the separator 4 is arranged so that the glass fiber mat 4b is in contact with the positive electrode plate 3. In the separator 4 in FIG. 2, when the back side is in contact with the positive electrode plate 3, the glass fiber mat 4b as shown on the front side is also provided on the back side.

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

Lead-acid batteries E1 to E16 and R1 to R12
Each lead-acid battery was prepared according to the following procedure.
(1) Preparation of separator A resin composition containing 100 parts by weight of polyethylene, 160 parts by weight of silica particles, 80 parts by weight of paraffin oil as a pore-forming agent, and 2 parts by weight of a penetrant is extruded into a sheet, stretched, and then a part of the pore-forming agent is removed to prepare a microporous membrane having ribs on one side.At this time, the cooling speed of the extruded sheet and the stretching ratio are adjusted so that the ratio R of the porous film obtained by the above-mentioned procedure is the value shown in Table 2 and Table 3.

The oil content of the separator determined by the above-mentioned procedure was 11 to 18% by mass, and the silica particle content was 60% by mass. The rib height determined by the above-mentioned procedure was 0.2 mm. The thickness of the porous film (thickness of the base portion) determined by the above-mentioned procedure is shown in Tables 2 and 3.

Next, the sheet-like porous film was folded in half so that the ribs were arranged on the inner surface to form a bag, and the overlapping ends were crimped to obtain a bag-like porous film (size when laid flat: length 117 mm x width 152 mm). The crimped part was 3 mm wide, located 2 mm inside from the side edge of the porous film. In Reference Examples 1 to 8 (R1 to R8), a rib was formed on the outer surface, and a bag-like porous film formed in the same manner as above was used as a separator, except that the rib height was 0.6 mm.

A glass fiber mat (size under atmospheric pressure: length 117 mm × width 143 mm, average fiber diameter: 17 μm, surface density: 60 g/m ² ) was attached with an adhesive to both outer surfaces of the bag-shaped porous film as shown in Figure 2. The width of the porous film was larger than that of the glass fiber mat, and an area of 4.5 mm wide where the glass fiber mat was not overlapped was formed on both side edges of the porous film.

The porous film ratio R, oil content, silica particle content, base thickness, rib height, glass fiber mat size, average fiber diameter, and surface density are values determined for the porous film or glass fiber mat before the lead-acid battery was fabricated, but are approximately the same as the values measured by the procedure described above for the porous film or glass fiber mat removed from the lead-acid battery after fabrication.

(2) Preparation 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 into the mesh of an expanded lattice made of a Pb-Ca-Sn alloy not containing antimony, and aged and dried to obtain an unformed positive electrode plate having a width of 137 mm, a height of 110 mm and a thickness of 1.6 mm.

(3) Preparation of negative electrode plate Lead oxide, carbon black, barium sulfate, lignin, reinforcing material (synthetic resin fiber), water and sulfuric acid were mixed to prepare a negative electrode paste. The negative electrode paste was filled into the mesh of an expanded lattice made of an antimony-free Pb-Ca-Sn alloy, and aged and dried to obtain an unformed negative electrode plate with a width of 137 mm, a height of 110 mm and a thickness of 1.3 mm. The amounts of carbon black, barium sulfate, lignin and synthetic resin fiber used were adjusted so that the contents of each component in the negative electrode plate taken out of a fully charged lead-acid battery were 0.3 mass%, 2.1 mass%, 0.1 mass% and 0.1 mass%, respectively.

(4) Preparation of lead-acid battery An unformed negative electrode plate was housed in a bag-shaped porous film of a separator. The negative electrode plate and the positive electrode plate were laminated via a separator so that the glass fiber mats attached to both outer surfaces of the bag were in contact with the positive electrode plate. In Reference Examples 1 to 8, the negative electrode plate and the positive electrode plate housed in a bag-shaped porous film were laminated. In this way, an electrode plate group was formed by seven unformed negative electrode plates and six unformed positive electrode plates.

The ears of the positive and negative plates were welded to the positive and negative shelf parts, respectively, using the cast-on-strap method. The plate group was inserted into a polypropylene battery case, electrolyte was poured in, and chemical formation was performed inside the battery case to assemble a flooded lead-acid battery with a rated voltage of 12 V and a rated capacity of 30 Ah (5-hour rate capacity (capacity when discharged at a current (A) that is 1/5 of the Ah value listed in the rated capacity)). Six plate groups were connected in series inside the battery case.

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

(5) Evaluation The XRD spectrum of the porous film of the separator of the lead-acid battery E7 measured by the above-mentioned procedure is shown in Figure 3. As shown in Figure 3, the first 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 second diffraction peak corresponding to the (200) plane was observed in the range of 2θ = 23 ° to 24.5 °. And, a halo due to the amorphous region was observed broadly in the wide range of 2θ = 17 ° to 27 °.

The separator or the obtained lead-acid battery was used to evaluate the puncture strength of the separator, the CCA performance, and the heavy load life performance of the lead-acid battery according to the procedures described above. The heavy load life performance was evaluated according to the procedures described above for a lead-acid battery that had been fully charged once. The puncture strength was evaluated as a ratio (%) to the puncture strength of the separator used in lead-acid battery R4, which was taken as 100. The CCA performance was evaluated as a ratio (%) of the terminal voltage at 30 seconds of each lead-acid battery to the terminal voltage at 30 seconds of lead-acid battery R4, which was taken as 100.

The evaluation results are shown in Tables 2 and 3. E1 to E16 are working examples. R1 to R12 are reference examples.

As shown in Table 2, in the separator without glass fiber mat, the CCA performance is affected by the thickness of the separator, and the smaller the thickness, the higher the CCA performance (R1 to R4). However, the smaller the thickness of the separator, the lower the heavy load life performance (R1 to R4). This is thought to be because when the separator is thin, the strength of the separator decreases, making it more likely to break, and the separator will end up with a short circuit due to the fallen positive electrode material, which will result in the end of its life. In the case of no glass fiber mat, even if the ratio R of the porous film is increased, there is no change in the CCA performance, but the strength is improved and the heavy load life performance is also improved to a certain extent (comparison between R1 to R4 and R5 to R8). For example, even if the porous film is very thin at 100 μm, the heavy load life performance is improved by 50 cycles, from 350 cycles to 400 cycles (comparison between R1 and R5). Even if the thickness of the porous film is large, the results are not very different, and the effect of increasing the ratio R is about 25 to 50 cycles.

When the porous film is laminated with a glass fiber mat, the shedding of the positive electrode material is reduced, so the heavy load life is expected to improve to some extent. However, when the porous film ratio R is less than 0.6 and the thickness is 100 μm, laminating with a glass fiber mat only improves the life by 25 cycles, from 350 to 375 cycles, and the improvement effect is small (compare R1 and R9). Even when the porous film is thicker, the results are not so different, and the improvement effect of laminating with a glass fiber mat on the heavy load life performance is about 25 to 50 cycles (compare R2 to R4 and R10 to R12). On the other hand, as the porous film becomes thicker, the resistance increases, so the CCA performance tends to decrease.

Considering the above results, it is expected that the heavy load life performance will improve by about 50 to 100 cycles even if the porous film ratio R is increased from 0.58 to 0.75 and laminated with a glass fiber mat. However, in reality, the heavy load life performance of E1 to E4 is improved by 125 to 150 cycles compared to R1 to R4, and a high value of 500 cycles or more is obtained. Moreover, the decrease in CCA performance is also suppressed to a low level in E1 to E4. A similar tendency is seen if the thickness of the porous film is 300 μm or less. From the viewpoint of obtaining excellent heavy load life performance and further improving CCA performance, the thickness of the porous film may be 250 μm or less or 200 μm or less.

As shown in Table 3, when the ratio R of the porous film is 0.60 or more, laminating with a glass fiber mat can ensure excellent heavy load life performance while ensuring high CCA performance (E5 to E16). Even if the thickness of the porous film is very small at 100 μm, a heavy load life performance of 450 cycles or more can be obtained.

In the examples, lead-acid batteries were produced and evaluated using porous films and plates of the above-mentioned sizes, but similar results were obtained even if the sizes of the porous films and plates were different from those described above.

The lead-acid battery separator according to the above aspect of the present invention is suitable for use in idling stop applications (such as lead-acid batteries for vehicles with idling stop systems) and as a starting power source for various vehicles (such as automobiles and motorcycles). The lead-acid battery separator can also be suitably used as a power source for industrial power storage devices such as electric vehicles (such as forklifts). Note that these applications are merely examples. Applications of the lead-acid battery separator and lead-acid battery according to the above aspect of the present invention are not limited to these. Idling stop (also called idling reduction) is sometimes referred to as IS.

1: Lead-acid battery 2: Negative electrode plate 3: Positive electrode plate 4: Separator 4a: Porous film 4b: Glass fiber mat 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: Vent plug 20: Crimping section 21: Area of porous film not covered with glass fiber mat

Claims (7)

A separator for a lead-acid battery,
The separator includes a laminate of a porous resin film and a glass fiber mat,
The porous film includes a crystalline region and an amorphous region,
In the X-ray diffraction spectrum of the porous film, the ratio R represented by A ₁ /(A ₁ +A ₂ ) is 0.60 or more;
_A1 is the area of the first diffraction peak having the maximum peak height among the diffraction peaks corresponding to the crystalline region,
_A2 is the area of a second diffraction peak having the second highest peak height among the diffraction peaks corresponding to the crystalline region. The lead-acid battery separator according to claim 1, wherein the porous film has a thickness of 100 μm or more and 300 μm or less. The separator for a lead acid battery according to claim 1 or 2, wherein the ratio R is 0.9 or less. The lead acid battery separator according to any one of claims 1 to 3, wherein the porous film contains polyolefin. The polyolefin contains at least ethylene units,
the first diffraction peak corresponds to the (110) plane of the crystalline region;
5. The lead acid battery separator according to claim 4, wherein the second diffraction peak corresponds to a (200) plane of the crystalline region. The lead-acid battery separator according to any one of claims 1 to 5, wherein the porous film has an area at least partially at an end that is not covered with the glass fiber mat. A lead-acid battery,
The lead-acid battery includes at least one cell including a plate 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 separator is a lead-acid battery separator according to any one of claims 1 to 6,
the fiberglass mat being in contact with the positive plate.

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