Separator for lead-acid battery and lead-acid battery including same

Abstract

SOLUTION: To provide a separator for a lead battery which includes a laminate of a resin-made porous film and a glass fiber mat, wherein the porous film includes a crystalline area and an amorphous area, in an X-ray diffraction spectrum of the separator, a degree of crystallization represented by 100×Ic / (Ic+Ia) is 20% or more, Ic is integrated intensity of a diffraction peak having a highest peak height in diffraction peaks corresponding to the crystalline area, and Ia is integrated intensity of a halo corresponding to the amorphous region.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a separator for a lead-acid battery and a lead-acid battery including the same. [Background technology]

[0002] Lead-acid batteries are used in a variety of applications, including automotive and industrial applications. Lead-acid batteries include a positive electrode plate, a negative electrode plate, a separator interposed between them, and an electrolyte. Separators for lead-acid batteries are required to have various performance characteristics. Porous polyolefin films are generally used as separators.

[0003] Patent Document 1 proposes a ribbed separator for lead-acid batteries containing 5 to 30 mass% of oil, which is obtained by heating and melting a raw material composition consisting of a mixture of 20 to 60 mass% polyolefin resin, 80 to 40 mass% inorganic powder, and 40 to 240 mass% mineral oil relative to the blend, and kneading the mixture while forming it into a ribbed sheet.The separator is then immersed in an immersion bath of an organic solvent that can dissolve the oil to extract and remove some of the oil, and then heated and dried.The separator is characterized in that the difference in oil content between the rib portion and the base portion of the separator is 5 mass% or less.

[0004] A porous film and a glass mat may be used together as a separator. For example, Patent Document 2 proposes a lead-acid battery including a positive electrode plate, a negative electrode plate, an electrolyte, and a separator, wherein the separator is made of a porous sheet and a glass mat, and the electrolyte contains aluminum ions in an amount of 0.02 mol / L or more and 0.2 mol / L or less, and lithium ions in an amount of 0.02 mol / L or more and 0.2 mol / L or less.

[0005] 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 an electrode plate group in which these are alternately stacked is housed in a battery case, characterized in that (a) a plurality of rib portions are provided on at least one side of the base portion of the synthetic resin thin film, (b) a glass mat is attached between each of the rib portions, and (c) glass mats are also attached to the outside of the rib portions at both ends, (d) when the glass mat is attached to the base portion 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 surfaces of the ribs, and (e) when the separator in which the glass mat is attached to the synthetic resin thin film is inserted into the electrode plate group and housed in the battery case of the lead-acid battery, the glass mat is compressed under pressure until the rib portion abuts against the positive plate, and the stacking pressure is 10 to 60 kPa. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-338631 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-84362 [Patent Document 3] Japanese Patent Application Laid-Open No. 2016-139455 Summary of the Invention [Problem to be solved by the invention]

[0007] In lead-acid batteries, repeated charge and discharge cycles cause the positive electrode material to soften. The provision of a glass fiber mat, as in Patent Documents 2 and 3, is advantageous in reducing the shedding of the softened positive electrode material. However, the separator, which is a laminate, has higher resistance than a porous film alone, resulting in reduced cold cranking ampere (CCA) performance. Reducing the thickness of the porous film can reduce the degradation of CCA performance. However, because the glass fiber mat is not very thick, the fallen positive electrode material or the edge of the current collector can easily penetrate the glass fiber mat. If the porous film constituting the laminate is too thin, the porous film will tear and short-circuit, shortening the battery life.

[0008] In lead-acid batteries, the oxidizing power of the positive electrode active material increases during overcharge, and oxidation is more likely to progress at high temperatures. Therefore, when the battery is overcharged at high temperatures (e.g., 75°C or higher), the porous film is more likely to oxidize, leading to a decrease in lifespan performance. Increasing the content of oil contained in the porous film as a pore-forming agent can somewhat suppress the decrease in lifespan performance even when the battery is overcharged at high temperatures. However, the resistance of the porous film increases, resulting in a decrease in CCA performance. Therefore, it is difficult to ensure high CCA performance while also ensuring lifespan performance when the battery is overcharged at high temperatures. Hereinafter, lifespan performance when the battery is overcharged at high temperatures (e.g., 75°C or higher) may be referred to as high-temperature overcharge lifespan performance. [Means for solving the problem]

[0009] 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 comprises a crystalline region and an amorphous region; In the X-ray diffraction spectrum of the separator, 100×I c / (I c +I a ) has a crystallinity of 20% or more, Ic 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. [Effects of the Invention]

[0010] In lead-acid batteries, it is possible to ensure high CCA performance while also ensuring excellent high-temperature overcharge life performance. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a partially cutaway perspective view showing the appearance and internal structure of a lead-acid battery according to an embodiment of the present invention; [Figure 2] FIG. 2 is a schematic plan view of the separator of FIG. [Figure 3] 1 is an X-ray diffraction spectrum of a porous film used in a separator of the lead-acid battery E7 of an example. DETAILED DESCRIPTION OF THE INVENTION

[0012] Lead-acid batteries are sometimes used under harsh conditions. One of their typical applications is in automobiles. In recent years, automobiles have become increasingly susceptible to overcharge due to traffic jams and constant use, such as in commercial vehicles. Furthermore, due to global warming, lead-acid batteries are increasingly used in higher temperature environments during the summer. When exposed to overcharge in high-temperature environments, the positive electrode material softens significantly, causing the positive electrode material to fall off due to vibration, resulting in the battery's end of life. The fallen positive electrode material can also cause oxidation and degradation of the separator, resulting in a short circuit, thereby shortening the battery's life. Therefore, in recent years, lead-acid batteries are increasingly required to have a higher level of high-temperature overcharge life performance than ever before.

[0013] When a separator contains oil, it can reduce oxidative degradation to some extent. However, the insulating oil clogs the separator's pores, increasing the separator's resistance and reducing CCA performance. Therefore, it is difficult to increase the oil content in the separator for high-performance lead-acid batteries that require high CCA performance. Furthermore, when a porous film is combined with a glass fiber mat, the glass fiber mat can somewhat suppress the shedding of the positive electrode material. However, it is difficult to completely suppress the shedding of the positive electrode material. Furthermore, because the glass fiber mat is not very thick, the fallen positive electrode material may penetrate the glass fiber mat. When the positive electrode material comes into contact with the porous film, it can tear due to oxidative degradation, causing a short circuit and terminating the battery's life. Thus, it is difficult to improve the high-temperature overcharge life of lead-acid batteries to a high level with conventional separators.

[0014] In view of the above, a separator for a lead-acid battery according to one aspect of the present invention 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 an X-ray diffraction (XRD) spectrum of the porous film, 100×I c / (I c +I a ) is 20% or more. c is the integrated intensity of the diffraction peak with the largest peak height (hereinafter sometimes referred to as the first diffraction peak) among the diffraction peaks corresponding to the crystalline region. a is the integrated intensity of the halo corresponding to the amorphous region.

[0015] Because the crystallinity of the porous film is 20% or higher, the oxidation resistance of the porous film itself can be improved. Therefore, even if high-potential positive electrode material that has fallen off penetrates the glass fiber mat and comes into contact with the porous film during high-temperature overcharge, tearing due to oxidative degradation is suppressed, thereby preventing the occurrence of short circuits. This improves high-temperature overcharge life. Even if the thickness of the porous film is reduced, oxidation degradation of the porous film can be suppressed, thereby preventing deterioration of CCA performance. Therefore, excellent high-temperature overcharge life can be ensured while maintaining high CCA performance. In other words, when the crystallinity of the porous film is increased, there is almost no trade-off between increased oxidation resistance and increased resistance, as occurs when increasing the oil content of conventional separators. Therefore, even high-performance lead-acid batteries can ensure excellent high-temperature overcharge life.

[0016] The porous film itself may also be used as a separator for a lead-acid battery. Unlike separators for lithium-ion secondary batteries, porous film separators for lead-acid batteries have a relatively large thickness. Furthermore, lead-acid batteries have a lower positive electrode potential during overcharge than lithium-ion secondary batteries. Therefore, sufficient oxidation resistance can be ensured by using oil or other additives under conventional operating conditions or usage patterns. Furthermore, the thicker the porous film, the more difficult it tends to be to increase its crystallinity. Furthermore, as the crystallinity increases, the porous film tends to become harder and more brittle. From this perspective, conventional separators for lead-acid batteries have not been designed to control their crystallinity. The crystallinity of porous films used in conventional separators for lead-acid batteries tends to be relatively low, at approximately 18% or less. Contrary to this conventional wisdom, in a lead-acid battery separator according to one aspect of the present invention, the crystallinity of the porous film laminated with a glass fiber mat is set to 20% or more, thereby ensuring high oxidation resistance while keeping the resistance of the porous film low and suppressing an increase in the resistance of the laminate with the glass fiber mat.

[0017] The thickness of the porous film is preferably 100 μm or more. When the thickness is within this range, the effect of suppressing oxidative degradation is further enhanced, and higher high-temperature overcharge life performance can be ensured. The thickness of the porous film is preferably 300 μm or less. In this case, the resistance of the porous film can be easily kept low, making it easier to obtain relatively high CCA performance.

[0018] The crystallinity is preferably 40% or less, which makes it easier to ensure the flexibility of the porous film and also makes it easier to manufacture.

[0019] The porous film preferably contains oil, which further enhances the effect of suppressing oxidation degradation of the porous film and ensures higher high-temperature overcharge life performance.

[0020] The porous film preferably contains a polyolefin, more preferably a polyolefin containing at least ethylene units. Such porous films are prone to oxidative degradation, but the crystallinity can be relatively easily increased. 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.

[0021] The porous film may have at least a portion of its edge that is not covered with the glass fiber mat. In such areas, the fallen positive electrode material may pierce the porous film or come into contact with the porous film, causing oxidative degradation, leading to a short circuit and a decrease in high-temperature overcharge life. However, even in such cases, the high crystallinity of the porous film can improve the oxidation resistance of the porous film, thereby reducing the occurrence of short circuits and reducing the decrease in high-temperature overcharge life.

[0022] The present invention also encompasses a lead-acid battery including the above-described lead-acid battery separator. The lead-acid battery includes at least one cell containing a plate assembly and an electrolyte. The plate assembly includes a positive electrode plate, a negative electrode plate, and the above-described separator interposed between the positive and negative electrode plates. The glass fiber mat of the separator is in contact with the positive electrode plate. Use of the above-described separator can reduce the resistance of the separator and ensure high CCA performance. The high oxidation resistance of the porous film prevents the porous film from being torn by shed positive electrode material, thereby suppressing the occurrence of short circuits and ensuring excellent high-temperature overcharge life.

[0023] The lead-acid battery may be a valve-regulated battery, but is preferably a flooded battery (vented battery), which is sometimes called a VRLA (Valve Regulated Lead-Acid Battery).

[0024] In this specification, the up-down direction of a lead-acid battery or its components (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 flooded battery, the lug is provided on the top of the electrode plate so as to protrude upward.

[0025] Hereinafter, separators and lead-acid batteries according to embodiments 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 embodiments.

[0026] (separator) The separator includes a laminate of a porous resin film and a glass fiber mat.

[0027] (porous film) A porous film contains crystalline regions in which the molecules of the constituent material of the porous film (specifically, the resin material) are arranged in a relatively regular pattern (i.e., highly ordered), and amorphous regions in which the molecules are less ordered. Therefore, in the XRD spectrum of a porous film, diffraction peaks due to the crystalline regions are observed, and scattered light due to the amorphous regions is observed as a halo. In the XRD spectrum of a porous film, 100×I c / (I c +I a ) is 20% or more, excellent high-temperature overcharge life performance can be obtained. c is the integrated intensity of the diffraction peak with the largest peak height (first diffraction peak) among the diffraction peaks corresponding to the crystalline region, and I a is the integrated intensity of the halo corresponding to the amorphous region.

[0028] 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 2θ range of 20° to 22.5°, and a diffraction peak corresponding to the (200) plane of the crystalline region is observed in the 2θ range of 23° to 24.5°. Furthermore, a halo of the amorphous region is observed in the 2θ range of 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.

[0029] The crystallinity of the porous film is 20% or more, and from the viewpoint of ensuring a higher high-temperature overcharge life performance, it may be 23% or more or 25% or more. The crystallinity may be 40% or less, 37% or less, or 35% or less. When the crystallinity is in this range, it is easy to ensure the flexibility of the separator and also easy to manufacture.

[0030] The crystallinity of the porous film may be 20% or more (or 23% or more) and 40% or less, 20% or more (or 23% or more) and 37% or less, 20% or more (or 23% or more) and 35% or less, 25% or more and 40% or less (or 37% or less), or 25% or more and 35% or less.

[0031] The integrated intensities of the diffraction peaks and halos are determined by fitting the diffraction peaks due to the crystalline regions and the halos due to the amorphous regions in the XRD spectrum of the porous film. The integrated intensity I of the first diffraction peak is calculated. c and the integrated intensity of the halo, I a The crystallinity can be calculated from the above formula using

[0032] The porous film includes, for example, a polymer material (hereinafter also referred to as a base polymer). Since the porous film includes a crystalline region, the base polymer usually includes a crystalline polymer. The porous film includes, for example, a polyolefin. A polyolefin is a polymer containing at least an olefin unit (i.e., a polymer containing at least a monomer unit derived from an olefin).

[0033] As the base polymer, polyolefin and other base polymers may be used in combination. The ratio of polyolefin to the entire base polymer contained in the porous film is, for example, 50% by mass or more, or may be 80% by mass or more, or may be 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 so high, the porous film tends to be easily deteriorated by oxidation. However, even in such a case, high oxidation resistance can be ensured by keeping the crystallinity within the above range.

[0034] Polyolefins include, for example, olefin homopolymers, 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. Furthermore, 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 that is copolymerizable with an olefin.

[0035] The polyolefin may, for example, be at least C 2-3 Polymers containing olefins as monomer units are also included. 2-3 The olefin may be at least one selected from the group consisting of ethylene and propylene. The polyolefin may be, for example, polyethylene, polypropylene, C 2-3 Copolymers containing olefins as monomer units (e.g., ethylene-propylene copolymers) are more preferred. Among polyolefins, polyolefins containing at least ethylene units (polyethylene, ethylene-propylene copolymers, etc.) are preferred. Polyolefins containing ethylene units (polyethylene, ethylene-propylene copolymers, etc.) may be used in combination with other polyolefins.

[0036] The porous film preferably contains oil, which can further enhance the effect of suppressing oxidation degradation of the porous film, thereby ensuring higher high-temperature overcharge life performance.

[0037] Oil refers to a hydrophobic substance that is liquid at room temperature (a temperature between 20°C and 35°C) and separates from water. Oils include naturally occurring oils, mineral oils, and synthetic oils. Mineral oils, synthetic oils, etc. are preferred. 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.

[0038] 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 degradation of the porous film is further enhanced. In addition, the resistance of the separator can be kept relatively low.

[0039] The porous film may be in a sheet form. Furthermore, a sheet-like porous film may be folded into an accordion shape and used as a separator. The porous film may be formed into a bag shape. Either the positive electrode plate or the negative electrode plate may be housed in the bag-like porous film.

[0040] The porous film may or may not have ribs. A porous film having ribs, for example, comprises a base portion and ribs extending from the surface of the base portion. The ribs may be provided on only one surface of the porous film or each base portion, or may be provided 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.

[0041] The thickness of the porous film is, for example, 90 μm or more. From the viewpoint of obtaining higher high-temperature overcharge life performance, 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 with such a small thickness of the porous film, sufficient oxidation resistance can be obtained and high high-temperature overcharge life performance can be ensured. The thickness of the porous film means the average thickness of the portion 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 means the average thickness of the base portion.

[0042] The thickness of the porous film may be 90 μm or more (or 100 μm or more) to 300 μm or less, 90 μm or more (or 100 μm or more) to 250 μm or less, 90 μm or more (or 100 μm or more) to 200 μm or less, or 90 μm or more (or 100 μm or more) to 150 μm or less.

[0043] When the porous film has ribs, the rib height may be 50 μm or more. Alternatively, the rib height may be 1.2 mm or less. The rib height is the height of the part protruding from the surface of the base part (protruding height).

[0044] In the above aspect of the present invention, the ribs of the porous film may be provided on the surface facing the negative electrode plate. In this case, the ribs are preferably provided on the portion of the porous film facing the negative electrode material. Providing the ribs on the negative electrode plate side facilitates diffusion of the electrolyte. 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.

[0045] When ribs are provided on the positive electrode plate side of the porous film, they may be provided in an area not covered with the glass fiber mat. When ribs are provided in a portion facing the positive electrode material, glass fiber mats may be disposed between adjacent ribs, as in Patent Document 2. However, in consideration of ease of lamination with the glass fiber mat, ribs may not be provided on the positive electrode plate side of the porous film.

[0046] The porous film may have an area at least partially at its edge that is not covered with the glass fiber mat. If this area comes into contact with a high-potential positive electrode material that has fallen off in a high-temperature overcharged state, 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 tear and a short circuit, which may result in the end of its life. However, in the above-described aspect of the present invention, even in such a case, the oxidation resistance of the porous film is improved, thereby suppressing oxidation degradation and tearing of the porous film and preventing the occurrence of a short circuit. The porous film is roughly rectangular, and typically has a total of four edges, including the top and bottom edges and both side edges. The width of the area of ​​the porous film that is not covered with the glass fiber mat at one edge (for example, w in Figure 2 described later) is p ) is, for example, 1 mm or more, and may be 2 mm or more. The width of this region may be, for example, 5 mm or less, 4.5 mm or less, or 4 mm or less. The porous film may have a region at the side edge (preferably both side edges) that is not covered with the glass fiber mat. When a bag-shaped porous film and a glass fiber mat are laminated together, a predetermined region at the side edge including the portion compressed into a bag shape is exposed outside the glass fiber mat.

[0047] The width of the 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.

[0048] A 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 extrusion, and then removing at least a portion of the pore-forming agent. By removing at least a portion of the pore-forming agent, micropores are formed in the base polymer matrix. After removing the pore-forming agent, the sheet-shaped porous film is dried as needed. For example, the ratio R can be adjusted by adjusting at least one parameter selected from the group consisting of the cooling rate of the sheet during extrusion, the stretching ratio during stretching, and the temperature during drying. For example, the ratio R tends to increase when the sheet is rapidly cooled during extrusion, the stretching ratio is increased, or the temperature during drying is reduced. The stretching may be performed by biaxial stretching, but is usually performed by uniaxial stretching. The sheet-shaped porous film may be folded into an accordion shape or processed into a bag shape as needed.

[0049] In the case of a porous film having ribs, the ribs may be formed on the sheet when the resin composition is extruded, or 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.

[0050] 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 degradation can be enhanced. One type of pore-forming agent may be used alone, or two or more types may be used in combination. 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), liquid pore-forming agents are classified as liquid pore-forming agents, and solid pore-forming agents are classified as solid pore-forming agents.

[0051] The liquid pore-forming agent is preferably the above-mentioned oil, and the solid pore-forming agent may be, for example, a polymer powder.

[0052] 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 mass or more per 100 parts by mass of the base polymer. The amount of pore-forming agent is, for example, 60 parts by mass or less per 100 parts by mass of the base polymer.

[0053] For example, a porous film containing oil can be formed by extracting and removing a portion 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, extraction conditions (extraction time, extraction temperature, solvent supply rate, etc.), etc.

[0054] 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.

[0055] 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, and may be 10% by mass or less.

[0056] The porous film (or the resin composition used to produce the porous film) may contain inorganic particles.

[0057] The inorganic particles are preferably, for example, ceramic particles, and examples of ceramics constituting the ceramic particles include at least one selected from the group consisting of silica, alumina, and titania.

[0058] The content of inorganic particles in the porous film may be, for example, 40% by mass or more, and may be, for example, 80% by mass or less, or 70% by mass or less.

[0059] (glass fiber 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, if the electrode plate at the end of the electrode plate group is a negative electrode plate, the bag-shaped porous film that houses this negative electrode plate may have the glass fiber mat laminated on the surface facing the positive electrode plate, and the surface that does not face the positive electrode plate may have the porous film exposed.

[0060] The glass fiber mat is a mat (or nonwoven fabric) made of glass fibers. The glass fiber mat may be a material called an absorbent glass mat (AGM).

[0061] The glass fiber mat may be formed entirely 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 components is usually 10% by mass or less, or 5% by mass or less.

[0062] 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 within this range, the effect of suppressing the detachment 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. Furthermore, the glass fiber mat can ensure relatively high flexibility and easily retain a relatively large amount of electrolyte.

[0063] 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.

[0064] The surface density of the glass fiber mat is, for example, 100 g / m 2 The surface density of the glass fiber mat is 250 g / m 2 It may be less than 200 g / m 2 It may be the following:

[0065] 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 they can be laminated (or fixed) using an adhesive. Alternatively, the porous film and the glass fiber mat can be laminated (or fixed) using welding (such as heat sealing) or mechanical bonding methods (such as gear sealing). Examples of adhesives include silicone-based adhesives, epoxy-based adhesives, and polyolefin-based adhesives. It is preferable to apply a small amount of adhesive so as not to increase the resistance of the separator. For example, it is preferable to apply the adhesive partially rather than entirely to the surface of the porous film or glass fiber mat to be bonded.

[0066] (Analysis or size measurement of porous films and glass fiber mats) (Preparing the separator) For the analysis or size measurement of porous films or glass fiber mats, unused separators or separators removed from fully charged lead-acid batteries are used. The separators removed from the lead-acid batteries are washed and dried prior to analysis or measurement.

[0067] The separator removed from the lead-acid battery is washed and dried using the following procedure: The separator 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 dry for at least 16 hours in an environment of 25°C ± 5°C.

[0068] In this specification, the fully charged state of a flooded lead-acid battery is defined by JIS D 5301:2019. More specifically, a fully charged state is defined as a state in which a lead-acid battery is charged in a water tank at 25°C ± 2°C at a current (A) 1 / 10 of the value listed for the rated capacity, measured every 15 minutes, until the terminal voltage (V) during charging or the electrolyte density converted to a temperature of 20°C shows a constant value to three significant digits three times consecutively. For a valve-regulated lead-acid battery, a fully charged state is defined as a state in which a battery is charged in an air tank at 25°C ± 2°C at a constant current / constant voltage of 2.23 V / cell at a current (A) 0.2 times the value listed for the rated capacity (unit: Ah), and charging is terminated when the charging current during constant voltage charging reaches a value (A) 0.005 times the value listed for the rated capacity (unit: Ah). The value listed for the rated capacity is in Ah. The unit of current set based on the value stated as rated capacity is A.

[0069] A fully charged lead-acid battery is a lead-acid battery that has already been chemically formed and is fully charged. The lead-acid battery may be fully charged immediately after chemical formation, or after a certain period of time has passed since chemical formation (for example, a lead-acid battery that is in use (preferably in the early stages of use) after chemical formation may be fully charged).

[0070] In this specification, a battery in its early stages of use refers to a battery that has not been in use for a long time and has not deteriorated much.

[0071] (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 perpendicular to the separator. A sample for measurement is prepared by peeling the glass fiber mat from the porous film and processing the area without adhesive into a strip. For porous films with ribs on the surface facing the positive electrode plate, the sample is processed so that the ribs are not included. The measurement and fitting of the XRD spectrum are performed under the following conditions. (Measurement conditions) Measurement device: RINT-TTR2, manufactured by Rigaku Corporation 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, Rigaku) ​​was used.

[0072] (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.

[0073] The height of the rib is determined by averaging the heights of the base portion of the rib from one surface measured at 10 arbitrarily selected points on the rib in a cross-sectional photograph of the separator.

[0074] (Oil content in porous film) In the separator, the glass fiber mat is peeled off from the porous film. The area of ​​the separator that is not coated with adhesive and faces the electrode material is cut into a strip to prepare a sample (hereinafter referred to as Sample A). If the porous film has ribs, Sample A is processed so that it does not include the ribs.

[0075] Approximately 0.5 g of sample A is taken and accurately weighed to determine the initial sample mass (m0). The weighed sample A is placed in an appropriately sized glass beaker and 50 mL of n-hexane is added. Next, ultrasonic waves are applied to the sample together with the beaker for approximately 30 minutes to dissolve the oil contained in sample A into n-hexane. Next, the sample is removed from the n-hexane and dried in the air at room temperature (a temperature between 20°C and 35°C), and then weighed to determine the mass (m1) of the sample after oil removal. The oil content is then calculated using the following formula. The oil content of 10 samples A is determined 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 x 100

[0076] (Content of inorganic particles in porous film) A portion of Sample A prepared in the same manner as above was taken, accurately weighed, and placed in a platinum crucible. It was then heated with a Bunsen burner until no white smoke was emitted. The resulting sample was then heated in an electric furnace (in an oxygen stream at 550°C ± 10°C) for approximately 1 hour to incinerate it, and the incinerated material was weighed. The percentage of the mass of the incinerated material relative to the mass of Sample A was calculated, and this was taken as the inorganic particle content (mass%). The inorganic particle content of 10 Samples A was determined, and the average value was calculated. The resulting average value was taken as the inorganic particle content in the porous film.

[0077] (Content of penetrant in porous film) A portion of Sample A prepared in the same manner as above was taken and accurately weighed. It was then dried for at least 12 hours at room temperature (20°C to 35°C) under reduced pressure below atmospheric pressure. The dried material was placed in a platinum cell and placed in a thermogravimetric analyzer. The temperature was raised from room temperature to 800°C ± 1°C at a rate of 10 K / min. The weight loss upon raising the temperature from room temperature to 250°C ± 1°C was taken as the mass of the penetrant, and the ratio (percentage) of the mass of the penetrant to the mass of Sample B was calculated, giving the penetrant content (mass%). A TA Instruments Q5000IR thermogravimetric analyzer was used. The penetrant content was determined for 10 Samples A and the average value was calculated. The average value obtained was taken as the penetrant content in the porous film.

[0078] (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 of the glass fiber mat portion of the separator in any cross section perpendicular to the length direction and averaging the diameter.

[0079] (Glass mat surface density) The portion of the separator facing the electrode material is cut, and the portion not coated with adhesive is sampled 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 and the mass of the porous film is measured. The mass of the glass fiber mat portion is determined 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 area is measured per 1 m 2 The mass (g) of the glass fiber mat per unit is calculated as the areal density.

[0080] (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 referred to as 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.

[0081] 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.

[0082] The lead alloy used for the positive electrode current collector is preferably a Pb-Ca alloy or a Pb-Ca-Sn alloy 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.

[0083] The positive electrode material contained in the positive electrode plate includes a positive electrode active material (lead dioxide or lead sulfate) that generates capacity through an oxidation-reduction reaction. The positive electrode material may also include other additives (such as reinforcing materials) as needed.

[0084] Examples of reinforcing materials include fibers (inorganic fibers, organic fibers, etc.). Examples of resins (or polymers) that constitute 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.

[0085] The content of the reinforcing material in the positive electrode material is, for example, 0.03 mass % or more, and the content of the reinforcing material in the positive electrode material is, for example, 0.5 mass % or less.

[0086] Unformed paste-type positive electrode plates are obtained by filling a positive electrode current 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 optionally other additives (such as reinforcing materials), and kneading them.

[0087] A positive electrode plate can be obtained by chemically forming an unformed positive electrode plate. Chemical formation can be performed by immersing an electrode plate assembly including the unformed positive electrode plate in an electrolyte containing sulfuric acid in a battery container of a lead-acid battery and then charging the electrode plate assembly. However, chemical formation may also be performed before assembling the lead-acid battery or the electrode plate assembly.

[0088] (negative plate) The negative electrode plate of a lead-acid battery is composed of a negative electrode current collector and a negative electrode material. The negative electrode material is the portion of the negative electrode plate excluding the negative electrode current collector. Note that an adhesive member such as that described above may be attached to the negative electrode plate. In this case, the adhesive member is included in the negative electrode plate. When the negative electrode plate includes an adhesive member, the negative electrode material is the portion of the negative electrode plate excluding the negative electrode current collector and the adhesive member.

[0089] The negative electrode current collector can be formed in the same manner as the positive electrode current collector.

[0090] The lead alloy used in the negative electrode current collector may be any of a Pb-Sb alloy, a Pb-Ca alloy, and a Pb-Ca-Sn alloy. These lead or lead alloys may further contain at least one additive element selected from the group consisting of Ba, Ag, Al, Bi, As, Se, and Cu. 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.

[0091] The negative electrode material contained in the negative electrode plate contains a negative electrode active material (lead or lead sulfate) that generates 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 also contain other additives (such as a reinforcing material) as necessary.

[0092] Examples of the organic shrinkage inhibitor include lignin, lignin sulfonic acid, synthetic organic shrinkage inhibitors (such as formaldehyde condensates of phenol compounds), etc. The negative electrode material may contain one type of organic shrinkage inhibitor, or may contain two or more types.

[0093] The content of the organic shrinkage inhibitor in the negative electrode material is, for example, 0.01% by mass or more, and 1% by mass or less.

[0094] Examples of the carbonaceous material include carbon black, graphite (artificial graphite, natural graphite, etc.), hard carbon, soft carbon, etc. The negative electrode material may contain one type of carbonaceous material or two or more types of carbonaceous materials.

[0095] The content of the carbonaceous material in the negative electrode material is, for example, 0.1 mass % or more, and may be, for example, 3 mass % or less.

[0096] The content of barium sulfate in the negative electrode material is, for example, 0.1% by mass or more, and 3% by mass or less.

[0097] Examples of the reinforcing material include fibers (inorganic fibers, organic fibers (such as organic fibers made of resin as described above for the reinforcing material of the positive electrode material)).

[0098] The content of the reinforcing material in the negative electrode material is, for example, 0.03 mass % or more, and the content of the reinforcing material in the negative electrode material is, for example, 0.5 mass % or less.

[0099] The negative electrode active material in the charged state is sponge lead, but the unformed negative electrode plate is usually made using lead powder.

[0100] The negative electrode plate can be formed by filling a negative electrode current collector with a negative electrode paste, aging and drying the paste to produce an unformed negative electrode plate, and then chemically forming the unformed negative electrode plate. The negative electrode paste is produced by adding water and sulfuric acid to lead powder, an organic shrinkage inhibitor, and various additives as needed, and kneading them. In the aging process, the unformed negative electrode plate is preferably aged at a temperature higher than room temperature and at a high humidity.

[0101] The formation can be carried out by immersing an electrode plate assembly including unformed negative plates in an electrolyte containing sulfuric acid in a battery jar of a lead-acid battery and then charging the electrode plate assembly. However, the formation can also be carried out before assembling the lead-acid battery or the electrode plate assembly. The formation produces spongy lead.

[0102] (electrolyte) The electrolyte is an aqueous solution containing sulfuric acid, and may be gelled if necessary.

[0103] 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.

[0104] 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 fully charged lead-acid battery.

[0105] The evaluation method for each characteristic will be explained below.

[0106] (1)CCA performance In accordance with JIS D 5301:2019, the starting ability of a lead-acid battery is evaluated using the current value at which the terminal voltage reaches 7.2V or higher 30 seconds after the start of discharge, using the following procedure. A higher current value indicates better starting ability and lower separator resistance. (a) After fully charging, place the battery in a cooling room at -18°C ± 1°C for at least 16 hours. (b) After confirming that the electrolyte temperature of one of the central cells is -18°C ± 1°C, discharge it for 30 seconds using the CCA390A. (c) Record the terminal voltage 30 seconds after the discharge begins.

[0107] (2) High temperature overcharge life performance The high-temperature overcharge life performance of a lead-acid battery is evaluated based on the life of the lead-acid battery at the time of a high-temperature overcharge durability test carried out according to the following procedure. (a) The battery shall be kept in an air chamber at 75°C ± 3°C throughout the entire test period. (b) Connect the storage battery to a life test device and continuously repeat the following discharge and charge cycles. This discharge and charge cycle is considered one life (1 cycle). Discharge: Discharge current 25.0A ±0.1A for 60 seconds ±1 second Charging: 600 seconds ±1 second at charging voltage 14.80V ±0.03V (limited current 25.0A ±0.1A) (c) During the test, leave the battery for 56 hours after every 480 cycles, then discharge the battery continuously for 30 seconds at the rated CCA390A and record the voltage at 30 seconds. Then, charge the battery as in (b). These discharges and charges are also counted in the lifespan (number of cycles). (d) The test is terminated when it is confirmed that the voltage measured at 30 seconds in the test (c) is 7.2 V or less and does not rise again, and the total number of cycles at this point is used as an index of life performance. The rated CCA is a measure of engine starting performance, and is the discharge current determined so that the voltage after 30 seconds is 7.2V or higher when discharged at a temperature of -18°C ± 1°C.

[0108] The items described in this specification can be combined in any manner.

[0109] FIG. 1 shows the 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 multiple cell chambers 14 by partition walls 13. Each cell chamber 14 contains one plate group 11. The opening of the battery case 12 is closed by a lid 15 that has 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 added. The vent plug 18 may have the function of venting gas generated in the cell chambers 14 to the outside of the battery.

[0110] Each electrode plate group 11 is formed by stacking a plurality of negative electrode plates 2 and positive electrode plates 3 with separators 4 interposed therebetween. In a cell chamber 14 located at one end of the battery case 12, a negative electrode shelf 6 that connects a plurality of negative electrode plates 2 in parallel is connected to a feedthrough connector 8, and a positive electrode shelf 5 that connects a plurality of positive electrode plates 3 in parallel is connected to a positive electrode column 7. The positive electrode column 7 is connected to a positive electrode terminal 17 outside the lid 15. In a cell chamber 14 located at the other end of the battery case 12, a negative electrode column 9 is connected to the negative electrode shelf 6, and a feedthrough 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 feedthrough connector 8 passes through a through hole provided in the partition wall 13, connecting the electrode plate groups 11 of adjacent cell chambers 14 in series.

[0111] 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 accommodates 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. On both side edges of the bag-shaped porous film 4a, a pressure-bonded portion 20 is provided linearly in the vertical direction so as to close the overlapped porous film 4a. On both side edges of the bag-shaped porous film 4a, an area 21 that is not covered by the glass fiber mat 4b is formed. The side edges of the glass fiber mat 4b are located inside the pressure-bonded portion 20. Therefore, the width w of the area 21 is 1 / 4. p is the width w from the side edge of the porous film 4a to the pressure-bonding portion 20 (more specifically, the outer position of the pressure-bonding portion 20). a is greater than.

[0112] The separator 4 is arranged in the lead-acid battery 1 so that the glass fiber mat 4b is in contact with the positive electrode plate 3. In the separator 4 of 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.

[0113] [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.

[0114] Lead-acid batteries E1 to E16 and R1 to R12 Each lead-acid battery was fabricated 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 paraffinic oil as a pore-forming agent, and 2 parts by weight of a penetrating agent was extruded into a sheet, stretched, and then partially removed to produce a microporous membrane with ribs on one side. The cooling rate and stretching ratio of the extruded sheet were adjusted so that the crystallinity of the porous film obtained by the above-mentioned procedure would be the values ​​shown in Tables 1 and 2.

[0115] The oil content of the separator determined by the above-mentioned procedure was 11 to 18 mass %, and the silica particle content was 60 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 1 and 2.

[0116] 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 located 2 mm inside from the side edge of the porous film and had a width of 3 mm. In Reference Examples 1 to 8 (R1 to R8), bag-like porous films formed in the same manner as above were used as separators, except that ribs were formed on the outer surface and the rib height was 0.6 mm.

[0117] As shown in Figure 2, glass fiber mats (size under atmospheric pressure: length 117 mm × width 143 mm, average fiber diameter: 17 μm, surface density: 60 g / m) were attached to both outer surfaces of the bag-shaped porous film. 2 The width of the porous film was larger than that of the glass fiber mat, and a 4.5 mm wide area was formed on both side edges of the porous film where the glass fiber mat did not overlap.

[0118] The crystallinity of the porous film, 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 above-described procedure for the porous film or glass fiber mat removed from the lead-acid battery after fabrication.

[0119] (2) Preparation of the 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 grid made of an antimony-free Pb-Ca-Sn alloy, and then aged and dried to obtain an unformed positive electrode plate measuring 137 mm wide, 110 mm high, and 1.6 mm thick.

[0120] (3) Preparation of negative electrode plate A negative electrode paste was prepared by mixing lead oxide, carbon black, barium sulfate, lignin, a reinforcing material (synthetic resin fiber), water, and sulfuric acid. The negative electrode paste was filled into the mesh of an expanded lattice made of an antimony-free Pb-Ca-Sn alloy, and then aged and dried to obtain an unformed negative electrode plate measuring 137 mm wide, 110 mm high, and 1.3 mm thick. The amounts of carbon black, barium sulfate, lignin, and synthetic resin fiber were adjusted so that the respective component contents of the negative electrode plate removed from a fully charged lead-acid battery were 0.3%, 2.1%, 0.1%, and 0.1% by mass, respectively.

[0121] (4) Preparation of lead-acid battery An unformed negative electrode plate was housed in a pouch-shaped porous film separator. The negative electrode plate and the positive electrode plate were stacked with the separator interposed between them 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 the pouch-shaped porous film were stacked. In this way, an electrode plate assembly was formed from seven unformed negative electrode plates and six unformed positive electrode plates.

[0122] The lugs of the positive and negative plates were welded to the positive and negative shelf sections, respectively, using the cast-on-strap method. The plate assembly 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) of 1 / 5 the Ah value listed on the rated capacity)). Six plate assembly groups were connected in series inside the battery case.

[0123] The electrolyte used was an aqueous sulfuric acid solution, and the specific gravity of the electrolyte after formation at 20°C was 1.285.

[0124] (5) Evaluation The XRD spectrum of the porous film separator of the lead-acid battery E7, measured using the procedure described above, 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 2θ range of 21.5° to 22.5°, and the second diffraction peak corresponding to the (200) plane was observed in the 2θ range of 23° to 24.5°. A broad halo due to the amorphous region was observed in the wide 2θ range of 17° to 27°.

[0125] The separators or the resulting lead-acid batteries were used to evaluate the CCA performance and high-temperature overcharge life performance of the lead-acid batteries according to the procedures described above. CCA performance was evaluated as the ratio (%) of the terminal voltage at 30 seconds of each lead-acid battery to the terminal voltage of lead-acid battery R4 at 30 seconds, which was set to 100. High-temperature overcharge life performance was evaluated as the ratio (%) of the number of cycles of each lead-acid battery to the number of cycles of lead-acid battery R4, which was set to 100.

[0126] The evaluation results are shown in Tables 1 and 2. E1 to E16 are examples, and R1 to R12 are reference examples.

[0127] [Table 1]

[0128] As shown in Table 1, for separators without a glass fiber mat, CCA performance is affected by separator thickness; the thinner the separator, the higher the CCA performance (R1–R4). However, the thinner the separator, the lower the high-temperature overcharge life performance (R1–R4). This is thought to be because a thin separator is more likely to tear when it comes into contact with the positive electrode material, making it more susceptible to short circuits. Without a glass fiber mat, increasing the crystallinity of the porous film does not affect CCA performance, but it does improve high-temperature overcharge life performance to some extent (compare R1–R4 with R5–R8). For example, even with a porous film thickness as thin as 100 μm, the high-temperature overcharge life performance improves by 15%, from 89% to 104% (compare R1 with R5). Even with a thicker porous film, the results are not significantly different; increasing the crystallinity only contributes to a 10–12% improvement.

[0129] Laminating a porous film with a glass fiber mat is expected to prevent the softened positive electrode material from shedding, thereby improving high-temperature overcharge life to some extent. However, when the porous film has a crystallinity of less than 20% and a thickness of 100 μm, laminating with a glass fiber mat only improves the cycle life by 9%, from 89% to 98% (comparison between R1 and R9). Even when the porous film is thicker, the results are not nearly as good; laminating with a glass fiber mat improves high-temperature overcharge life by only 7–10% (comparison between R2–R4 and R10–R12). On the other hand, as the porous film thickness increases, resistance increases, which tends to reduce CCA performance.

[0130] Considering the above results, it is expected that increasing the crystallinity of the porous film from 18% to 25% and laminating it with a glass fiber mat would only improve the high-temperature overcharge life performance by about 14 to 22%. However, in reality, E1 to E4 achieve a 36 to 41% improvement in high-temperature overcharge life performance compared to R1 to R4, achieving a high value of 130 to 138%. Furthermore, E1 to E4 also achieve a low decrease in CCA performance. A similar trend is observed when the porous film thickness is 300 μm or less. To obtain excellent high-temperature overcharge life performance and further improve CCA performance, the porous film thickness may be set to 250 μm or less or 200 μm or less.

[0131] [Table 2]

[0132] As shown in Table 2, when the crystallinity of the porous film is 20% or more, laminating it with a glass fiber mat can ensure high CCA performance while also ensuring excellent high-temperature overcharge life (E5 to E16). Even when the porous film is very thin (100 μm), a high-temperature overcharge life of 115% or more can be achieved.

[0133] In the examples, lead-acid batteries were produced and evaluated using porous films and electrode plates of the above-mentioned sizes, but similar results can be obtained even if the sizes of the porous films and electrode plates are different from those described above. [Industrial Applicability]

[0134] The lead-acid battery separator according to the above aspect of the present invention is suitable for, for example, 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. The applications of the lead-acid battery separator and the 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. [Explanation of symbols]

[0135] 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 pole 8: Through-connector 9: Negative pole 11: Plate group 12:Battery container 13: Bulkhead 14: Cell Room 15: Lid 16: Negative terminal 17: Positive terminal 18: Liquid vent plug 20: Crimping section 21: Area of ​​porous film not covered with glass fiber mat

Claims

1. 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 has a thickness of 100 μm or more and 300 μm or less and contains oil at a content of 11% by mass or more and 18% by mass or less, the porous film comprises a crystalline region and an amorphous region; In the X-ray diffraction spectrum of the porous film, 100×I ｃ / (I ｃ +I ａ ) has a crystallinity of 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.

2. 2. The separator for a lead-acid battery according to claim 1, wherein the crystallinity is 40% or less.

3. The lead-acid battery separator according to claim 1 or 2, wherein the porous film contains a polyolefin.

4. The polyolefin contains at least ethylene units, 4. The lead-acid battery separator according to claim 3, wherein a first diffraction peak corresponding to a (110) plane of the crystalline region and a second diffraction peak corresponding to a (200) plane of the crystalline region are observed in the X-ray diffraction spectrum.

5. The lead-acid battery separator according to any one of claims 1 to 4, wherein the porous film has an area at least in part of an end portion that is not covered with the glass fiber mat.

6. A lead-acid battery, The lead-acid battery includes at least one cell including a plate pack 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 5, The glass fiber mat is in contact with the positive electrode plate.

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