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

Abstract

To provide a separator for lead storage battery which can be contributed to improvement of lifetime performance and improvement of productivity.SOLUTION: A separator for lead storage battery includes a porous film and a carbon material disposed on a surface of the porous film. The porous film includes a crystalline region and an amorphous region. In an X-ray diffraction spectrum of the porous film, a ratio R represented by A1 / (A1+A2) is 0.70 or more. A1 is an area of a first diffraction peak with a maximum peak height in diffraction peaks corresponding to the crystalline region. A2 is an area of a second diffraction peak with a second higher peak height in the diffraction peaks corresponding to the crystalline 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 positive and negative electrode plates, a separator interposed between them, and an electrolyte. Separators for lead-acid batteries are required to have various performance characteristics.

[0003] Patent Document 1 discloses a ribbed separator for lead-acid batteries, which is obtained by heating and melting a raw material composition comprising 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 while kneading, forming the raw material composition into a sheet having ribs. The sheet is then immersed in an immersion bath of an organic solvent capable of dissolving the oil to extract and remove a portion of the oil, and then heated and dried. The ribbed separator contains 5 to 30 mass% of the oil, and the difference in oil content between the rib portion and the base portion of the separator is 5 mass% or less.

[0004] Patent Document 2 discloses "a lead-acid battery separator, the lead-acid battery separator comprising a porous membrane and / or a fibrous mat, and one or more conductive elements or nucleating additives within or on the porous membrane and / or the fibrous mat." [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-338631 [Patent Document 2] Japanese Patent Application Publication No. 2020-533741 Summary of the Invention [Problem to be solved by the invention]

[0006] Current lead-acid batteries, such as those used in vehicles with idle-stop systems, are required to perform under different operating conditions than past lead-acid batteries. To address this demand, there has always been a need to improve the lifespan and productivity of lead-acid batteries. Therefore, new technologies that can contribute to improving lifespan and productivity are needed. [Means for solving the problem]

[0007] One aspect of the present disclosure relates to a separator for a lead-acid battery, the separator for a lead-acid battery comprising a porous membrane and a carbon material disposed on a surface of the porous membrane, the porous membrane comprising a crystalline region and an amorphous region, wherein an X-ray diffraction spectrum of the porous membrane has a ratio R expressed as A1 / (A1+A2) of 0.70 or greater, where A1 is the area of ​​a first diffraction peak having the greatest peak height among the diffraction peaks corresponding to the crystalline region, and A2 is the area of ​​a second diffraction peak having the second greatest peak height among the diffraction peaks corresponding to the crystalline region.

[0008] Another aspect of the present disclosure relates to a lead-acid battery including at least one cell containing an electrode plate assembly and an electrolyte, the electrode plate assembly including a positive electrode plate, a negative electrode plate, and a separator interposed between the positive electrode plate and the negative electrode plate, the separator being the lead-acid battery separator of the above aspect. [Effects of the Invention]

[0009] According to the present disclosure, a separator capable of improving the life performance and productivity of lead-acid batteries can be obtained. [Brief explanation of the drawings]

[0010] [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] 1 is an X-ray diffraction spectrum of an example of a separator for a lead-acid battery produced in an example. [Figure 3] 10 is a graph showing some of the results of Experimental Example 3. [Figure 4] 10 is a graph showing another part of the results of Experimental Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0011] Below, examples of embodiments according to the present disclosure will be described, but the present disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be exemplified, but other numerical values ​​and other materials may be applied as long as the effects of the present disclosure are obtained. In this specification, the expression "numerical value A to numerical value B" includes numerical value A and numerical value B and can be read as "numerical value A or more and numerical value B or less." In the following description, when lower and upper limits are exemplified for numerical values ​​of specific physical properties or conditions, any of the exemplified lower limits can be arbitrarily combined with any of the exemplified upper limits, as long as the lower limit is not equal to or greater than the upper limit.

[0012] (Lead-acid battery separator) A lead-acid battery separator according to one aspect of the present invention includes a porous membrane and a carbon material disposed on the surface of the porous membrane. Hereinafter, the porous membrane may be referred to as a "porous membrane (F)." The porous membrane (F) includes a crystalline region and an amorphous region. In an X-ray diffraction (XRD) spectrum of the porous membrane (F), the ratio R, expressed as A1 / (A1+A2), is 0.70 or greater. Here, A1 is the area of ​​the diffraction peak (first diffraction peak) having the largest peak height among the diffraction peaks corresponding to the crystalline region. A2 is the area of ​​the diffraction peak (second diffraction peak) having the second highest peak height among the diffraction peaks corresponding to the crystalline region.

[0013] Lead-acid batteries are sometimes used under harsh conditions. One of the typical applications of lead-acid batteries is in automobiles. In recent years, there have been increasing opportunities for lead-acid batteries to be exposed to overcharge due to automobiles being caught in traffic jams or being used constantly like commercial vehicles. In addition, with global warming, there are more opportunities for lead-acid batteries to be used in higher temperature environments in the summer. Therefore, in recent years, there has been a growing demand for lead-acid batteries to have even higher levels of life performance (for example, high-temperature overcharge life performance) than before.

[0014] Oxidative degradation of the separator is one of the factors shortening the lifespan of lead-acid batteries. When ribs are provided on the surface of the separator facing the positive electrode plate, gaps are formed between the separator and the positive electrode plate. Therefore, providing ribs tends to reduce oxidative degradation of the separator. However, as lead-acid batteries become more powerful, more thin electrodes are often used per cell than in the past. Therefore, providing ribs alone is not sufficient to suppress oxidative degradation of the separator. Oxidative degradation of the separator can also be reduced to some extent when the separator contains oil. However, insulating oil tends to clog the separator's pores, increasing the separator's resistance and reducing the reactivity of the electrodes. Therefore, it is difficult to increase the oil content in the separator for high-performance lead-acid batteries. As such, it is difficult to improve the lifespan of lead-acid batteries to a high level using conventional separators.

[0015] The ratio R indicates the crystallinity of the porous membrane (F). That is, a high ratio R indicates high crystallinity of the porous membrane (F). Since the ratio R of the porous membrane (F) is 0.70 or higher, the oxidation resistance of the porous membrane (F) is high. Unlike increasing oxidation resistance by using oil, increasing oxidation resistance by increasing crystallinity has almost no disadvantage such as increased resistance. Therefore, even high-performance lead-acid batteries can ensure excellent life performance.

[0016] Unlike separators for lithium-ion secondary batteries, separators for lead-acid batteries have a relatively large thickness. Furthermore, because lead-acid batteries have a lower positive electrode potential during overcharge than lithium-ion secondary batteries, sufficient oxidation resistance can be ensured in conventional operating environments or configurations using ribs, oil, etc. Furthermore, the thicker the separator, the more difficult it tends to be to increase crystallinity. Furthermore, as crystallinity increases, the separator tends to become harder and more brittle. From this perspective, conventional efforts have not been made to control the crystallinity of separators for lead-acid batteries. The ratio R of conventional separators for lead-acid batteries has been at least 0.65 or less. Contrary to this conventional wisdom, the ratio R of the porous membrane (F) used in the separator of this embodiment is set to 0.70 or more. This significantly improves life performance (e.g., high-temperature overcharge life performance).

[0017] The lifespan of a lead-acid battery is also significantly reduced by uneven electrolyte concentration (stratification). In lead-acid batteries, the concentration of the electrolyte in the upper part of the battery can be lower than that in the lower part, which reduces the battery's lifespan performance.

[0018] The separator of this embodiment includes a carbon material disposed on its surface. This carbon material comes into contact with an electrode (positive electrode or negative electrode) in a lead-acid battery, and is therefore electrically connected to the electrode. As a result, when the lead-acid battery is charged (e.g., at the end of charging), water may be electrolyzed in the carbon material, generating gas. The generated gas agitates the electrolyte, thereby suppressing stratification of the electrolyte.

[0019] However, when water electrolysis occurs on the surface of the separator, it is important to suppress oxidation of the separator due to the generated oxygen gas. The separator of this embodiment uses a resin film (F) with high crystallinity, so it is possible to suppress oxidation of the separator.

[0020] Furthermore, lead-acid batteries are being developed with a large number of thin plates to improve their performance. However, in lead-acid batteries that use a large number of thin plates, the rate of defects during manufacturing increases due to insufficient separator strength. Therefore, increasing separator strength is particularly important for improving the reliability and productivity of high-performance lead-acid batteries.

[0021] The present inventors have found that a separator having strength beyond expectations can be obtained by combining the resin film (F) with a carbon material. That is, the separator of this embodiment makes it possible to construct a high-performance lead-acid battery with long life and high productivity.

[0022] The thickness of the separator is preferably 100 μm or more and 300 μm or less. When the thickness is in this range, the effect of suppressing oxidation degradation of the separator is further enhanced, and the life performance can be further improved.

[0023] The ratio R is preferably 0.90 or less, which makes it easier to ensure the flexibility of the separator and also makes it easier to manufacture.

[0024] The separator preferably contains oil, which further enhances the effect of suppressing oxidation degradation of the separator, ensuring a longer lifespan.

[0025] The tortuosity of the pores of the porous membrane (F) is preferably at least 5. In this case, the strength of the separator can be further increased.

[0026] The porous film (F) preferably contains a polyolefin, more preferably a polyolefin containing at least an ethylene unit. Although such a porous film (F) tends to have a relatively low strength, the ratio R can be adjusted relatively easily, and the strength of the porous film (F) can be increased by adjusting the ratio R. When the porous film (F) contains a polyolefin containing at least an ethylene unit, 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.

[0027] (carbon materials) As the carbon material, a conductive carbon material can be used. Examples of conductive carbon materials include graphite, activated carbon, carbon black, carbon fiber, and carbon nanotubes. Examples of conductive carbon black include acetylene black, ketjen black, and high surface area carbon black. From the viewpoint of productivity, it is preferable to use carbon black, and for example, it is preferable to use acetylene black, high surface area carbon black, or ketjen black. The carbon material may be at least one selected from the group consisting of conductive carbon black and conductive carbon fiber. The carbon material may be arranged in the form of a layer on the surface of the porous membrane (F). The method of arranging the carbon material will be described later.

[0028] The carbon material may be disposed on only one of the two main surfaces of the porous membrane (F) (the main surface on the positive electrode plate side or the main surface on the negative electrode plate side), or on both main surfaces. In other words, the carbon material is present on at least one surface of the separator. In a preferred example, the carbon material is disposed on only one main surface of the porous membrane (F). As will be described later, the carbon material may be disposed on only the main surface of the porous membrane (F) on the negative electrode plate side.

[0029] The carbon material may be arranged in a layered form so as to cover the main surface of the porous membrane (F), or may be arranged in a non-layered form. Examples of a non-layered form include a form in which the carbon material is arranged in the form of dispersed islands. When the carbon material is arranged in a layered form, the thickness thereof may be 5 μm or more from the viewpoint of increasing the strength of the separator. The thickness of the carbon material layer may be in the range of 5 μm to 30 μm (for example, in the range of 10 μm to 20 μm). The thickness of the carbon material layer can be measured in the same manner as the thickness of the separator.

[0030] The content of the carbon material in the separator (the carbon material disposed on the surface of the porous membrane (F)) may be 2% by mass or more, and preferably 3% by mass or more. By setting the content to 2% by mass or more, it is possible to particularly improve the oxidation resistance and strength of the separator. The content may be 40% by mass or less, or 30% by mass or less.

[0031] (Porous membrane (F)) The porous film (F) contains crystalline regions where the molecules of the constituent materials of the porous film (F) are arranged in a relatively regular pattern (i.e., highly ordered) and amorphous regions where the order is low. Therefore, in the XRD spectrum of the porous film (F), 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 the porous film (F), a ratio R expressed as A1 / (A1+A2) of 0.70 or greater ensures excellent life performance. Here, A1 is the area of ​​the diffraction peak with the largest peak height (first diffraction peak) among the diffraction peaks corresponding to the crystalline regions, and A2 is the area of ​​the diffraction peak with the second highest peak height (second diffraction peak) among the diffraction peaks corresponding to the crystalline regions.

[0032] For example, in the XRD spectrum of a porous film (F) 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 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.

[0033] The ratio R is 0.70 or more. From the viewpoint of ensuring higher strength of the separator, the ratio R may be 0.75 or more. The ratio R may be 0.90 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 the manufacturing is also easy.

[0034] The ratio R may be 0.70 or more and 0.90 or less, or 0.75 or more and 0.90 or less. Within these ranges, the upper limit may be 0.85 or less, or 0.80 or less.

[0035] The diffraction peak areas are determined by fitting the diffraction peaks due to the crystalline region in the XRD spectrum of the porous membrane (F). 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.

[0036] The porous membrane (F) contains a polymer material (hereinafter also referred to as a base polymer). Since the porous membrane (F) contains a crystalline region, the base polymer usually contains a crystalline polymer. The porous membrane (F) contains, 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).

[0037] As the base polymer, polyolefin may be used in combination with another base polymer. The ratio of polyolefin to the entire base polymer contained in the porous film (F) 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 alone. When the ratio of polyolefin is so high, the oxidation resistance of the porous film (F) tends to be low. However, even in such a case, by setting the ratio R within the above range, a long life performance can be ensured.

[0038] 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.

[0039] 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.

[0040] The separator (more specifically, the porous membrane (F)) preferably contains oil. When the separator contains oil, the effect of suppressing oxidative degradation of the separator can be further enhanced, thereby ensuring a longer lifespan. Oil refers to a hydrophobic substance that is liquid at room temperature (a temperature of 20°C or higher and 35°C or lower) and separates from water. Oils include naturally occurring oils, mineral oils, and synthetic oils. Preferred oils include mineral oils and synthetic oils. Examples of oils include paraffin oil and silicone oil. The separator may contain one type of oil or a combination of two or more types of oil.

[0041] The oil content in the separator 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 oxidation degradation of the separator is further enhanced. In addition, the resistance of the separator can be kept relatively low.

[0042] The separator may be in a sheet form. Alternatively, a sheet folded into an accordion shape may be used as the separator. The separator may be formed in a bag form. Either the positive electrode plate or the negative electrode plate may be wrapped in the bag-shaped separator.

[0043] The separator may or may not have ribs. A separator with ribs includes, for example, a base portion and ribs extending from the surface of the base portion. The ribs may be provided on only one surface of the separator or each base portion, or on both surfaces. The base portion of the separator refers to the portion of the separator that excludes protrusions such as ribs, and is the sheet-like portion that defines the outer shape of the separator.

[0044] The thickness of the separator is 100 μm or more. From the viewpoint of obtaining a higher life performance, the thickness of the separator is preferably 150 μm or more. The thickness of the separator is, for example, 300 μm or less. From the viewpoint of keeping the resistance of the separator low, the thickness of the separator may be 250 μm or less or 200 μm or less. The thickness of the separator means the average thickness of the portion of the separator facing the electrode material. When the separator has a base portion and a rib standing on at least one surface of the base portion, the thickness of the separator is the average thickness of the base portion. When an attachment member (such as a mat or pasting paper) is attached to the separator, the thickness of the attachment member is not included in the thickness of the separator.

[0045] The thickness of the separator may be 100 μm or more and 300 μm or less, 100 μm or more and 250 μm or less, or 100 μm or more and 200 μm or less, and the lower limit of these ranges may be 120 μm or more, or 150 μm or more.

[0046] When the separator has ribs, the rib height may be 0.05 mm or more. Alternatively, the rib height may be 1.2 mm or less. The rib height is the height of the part that protrudes from the surface of the base part (protrusion height).

[0047] The height of the ribs provided in the region of the separator facing the positive electrode plate may be 0.4 mm or more, and the height of the ribs provided in the region of the separator facing the positive electrode plate may be 1.2 mm or less.

[0048] The carbon material is disposed on the surface of the formed porous membrane (F). There is no particular limitation on the method for disposing the carbon material. For example, the carbon material may be formed by applying a carbon material, a composition containing a carbon material, or a dispersion containing a carbon material to the surface of the porous membrane (F). There is no particular limitation on the application method, and doctor blade methods, roller coating methods, spray coating methods, immersion methods, vapor deposition methods, and other printing methods may be used. Examples of dispersions containing a carbon material include dispersions in which a carbon material is dispersed in a dispersion medium (water and / or an organic solvent). The amount and thickness of the carbon material disposed on the surface of the porous membrane (F) can be adjusted by controlling the amount of carbon material applied.

[0049] The porous membrane (F) 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. Removing at least a portion of the pore-forming agent forms micropores in the base polymer matrix. After removing the pore-forming agent, the sheet-shaped porous membrane (F) 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, rapid cooling of the sheet during extrusion, increasing the stretching ratio, or decreasing the temperature during drying tends to increase the ratio R. The stretching may be performed by biaxial stretching, but is usually performed by uniaxial stretching. The sheet-shaped separator may be folded into an accordion shape or processed into a bag shape as needed. When a separator having a carbon material disposed on only one main surface of the porous membrane (F) is processed into a bag shape, the carbon material is disposed on either the inner surface or the outer surface of the bag.

[0050] In a separator having ribs, the ribs may be formed when the resin composition is extruded into a sheet, or after the resin composition is molded into a sheet or after the pore-forming agent is removed, by pressing the sheet with a roller having grooves corresponding to each rib.

[0051] 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 separator containing oil is obtained, which further enhances the effect of suppressing oxidative degradation. 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.

[0052] The liquid pore-forming agent is preferably the above-mentioned oil, and the solid pore-forming agent is, for example, a polymer powder.

[0053] The amount of the pore-forming agent in the porous membrane (F) may vary depending on the type of pore-forming agent. The amount of the pore-forming agent in the porous membrane (F) is, for example, 30 parts by mass or more per 100 parts by mass of the base polymer. The amount of the pore-forming agent is, for example, 60 parts by mass or less per 100 parts by mass of the base polymer.

[0054] For example, a porous membrane (F) containing oil is 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 membrane (F) can be adjusted by adjusting the type and composition of the solvent, extraction conditions (extraction time, extraction temperature, solvent supply rate, etc.), etc.

[0055] 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.

[0056] The content of the penetrant in the porous membrane (F) is, for example, 0.01% by mass or more, and may be 0.1% by mass or more, and the content of the penetrant in the porous membrane (F) may be 10% by mass or less.

[0057] The porous membrane (F) (or the resin composition used to produce the porous membrane (F)) may contain inorganic particles. Note that these inorganic particles do not include carbon materials disposed on the surface of the porous membrane (F).

[0058] 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.

[0059] The content of inorganic particles other than carbon materials in the porous membrane (F) may be, for example, 40% by mass or more. The content of inorganic particles is, for example, 80% by mass or less, or may be 70% by mass or less.

[0060] The tortuosity of the pores of the porous membrane (F) is, for example, 5 or more, and may be 20 or more. The tortuosity of the pores is, for example, 150 or less, and may be 70 or less. By making the tortuosity of the pores 5 or more, the strength of the separator can be further increased. In addition, a high permeation short-circuit suppression effect can be obtained, and a high capacity can be obtained.

[0061] In the separator, the tortuosity of the pores may be 5 or more (or 20 or more) and 150 or less, or 5 or more (or 20 or more) and 70 or less.

[0062] The tortuosity of the pores can be determined by mercury intrusion porosimetry and is expressed by the following formula:

[0063]

number

[0064] The degree of tortuosity can be adjusted by adjusting the affinity between the pore-forming agent and the base polymer, by selecting the type and / or particle size of the inorganic particles, and / or by adjusting the amount of functional groups and / or atoms present on the surface of the inorganic particles. The degree of tortuosity can also be adjusted by adjusting the type and composition of the solvent used to extract and remove the pore-forming agent, and the extraction conditions (extraction time, extraction temperature, solvent supply rate, etc.).

[0065] (Separator analysis or size measurement) (Preparing the separator) For separator analysis or size measurement, an unused separator or a separator removed from a lead-acid battery in a fully charged state at the beginning of use is used. The separator removed from the lead-acid battery is washed and dried prior to analysis or measurement. The XRD spectrum of the porous membrane (F) may be measured using the porous membrane (F) before a carbon material is disposed on its surface. Furthermore, the XRD spectrum of the porous membrane (F) having a carbon material disposed on only one side may be measured using the surface on which the carbon material is not disposed.

[0066] 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. For separators with carbon material on both sides, the carbon material is removed by polishing before measuring the XRD spectrum.

[0067] In this specification, the fully charged state of a lead-acid battery is defined by JIS D 5301:2019. More specifically, the 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) that is 1 / 10 of the value listed as the rated capacity, until the terminal voltage (V) during charging or the electrolyte density converted to a temperature of 20°C, measured every 15 minutes, shows a constant value to three significant digits three times in a row. The value listed as the rated capacity is expressed in units of Ah (ampere-hours). The unit of current set based on the value listed as the rated capacity is A (ampere).

[0068] 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).

[0069] 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.

[0070] (XRD spectrum) The XRD spectrum of the porous membrane (F) is measured by irradiating the surface of the porous membrane (F) with X-rays perpendicular to the surface. The measurement sample is prepared by processing the part of the porous membrane (F) facing the electrode material into a strip. For porous membranes (F) with ribs, the base part is processed into a strip so as not to include the ribs. The measurement and fitting of the XRD spectrum are performed under the following measurement conditions.

[0071] (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] (Separator thickness and rib height) The thickness of the separator is determined by measuring the thickness at five randomly selected points on a cross-sectional photograph of the separator and averaging the measurements. If the carbon material is layered, the thickness of the carbon material layer can be determined in the same way.

[0073] The rib height is determined using the following procedure. First, ten random locations on the rib are selected from a cross-sectional photograph of the separator. Next, the rib height (height from the surface of the base) is measured at each of the ten selected locations. Next, the rib height is determined by averaging the heights measured at the ten locations.

[0074] (Oil content in porous membrane (F)) The portion of the separator facing the electrode material is cut into a strip to prepare a sample (hereinafter referred to as Sample A). At this time, the carbon material on the surface of the porous membrane (F) is removed by polishing to prepare the sample. For separators with ribs, Sample A is prepared by cutting the base portion into a strip so as not to 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 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 membrane (F). Oil content (mass%) = 100 × (m0 - m1) / m0

[0076] (Content of inorganic particles in porous membrane (F)) 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 ashes were weighed. The percentage of the mass of the ashes relative to the mass of Sample A was calculated, and this was taken as the inorganic particle content (mass%). The inorganic particle content was determined for 10 Samples A, and the average value was calculated. The resulting average value was taken as the inorganic particle content (inorganic particles other than carbon materials) in the porous film (F).

[0077] (Content of penetrant in porous membrane (F)) A portion of Sample A prepared in the same manner as above was taken, accurately weighed, and 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 membrane (F).

[0078] (bending degree) The terms in the above formula for determining the tortuosity (density, total pore volume, permeability, and differential pore distribution) are determined by the following procedure. First, a portion of the porous membrane (F) facing the electrode material is cut into a size of 20 mm length x 5 mm width to prepare a sample (sample B). Next, the sample is measured using a mercury porosimeter under the following conditions to determine the above terms. Mercury porosimeter: Autopore IV9510, manufactured by Shimadzu Corporation Measurement pressure range: 4 psia (≒ 27.6 kPa) to 60,000 psia (≒ 414 MPa) Pore ​​size distribution: 0.01 μm to 50 μm

[0079] (lead acid battery) A lead-acid battery according to one aspect of the present invention includes at least one cell containing an electrode plate assembly and an electrolyte. The electrode plate assembly 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 the lead-acid battery separator of this embodiment. Use of the separator of this embodiment can significantly improve the life performance and productivity of the lead-acid battery.

[0080] The lead acid battery may be a valve regulated lead acid battery (VRLA type battery), but is preferably a flooded battery (vented type battery).

[0081] The carbon material of the separator may be disposed on both of the two main surfaces of the porous membrane (F), or on the main surface on the positive electrode plate side or the negative electrode plate side. For example, the carbon material of the separator may be disposed on the main surface on the negative electrode plate side of the two main surfaces of the porous membrane (F). When water electrolysis occurs during charging, oxygen gas is generated on the positive electrode side. By disposing the carbon material on the negative electrode plate side, it is possible to prevent oxygen gas from being generated in the separator and oxidizing the porous membrane (F).

[0082] 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. Note that 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. Examples of the components of a lead-acid battery are described below.

[0083] (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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] (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.

[0092] The negative electrode current collector can be formed in the same manner as the positive electrode current collector. At least one of the positive electrode current collector and the negative electrode current collector may be a current collector formed by expanding. In electrode plates using a current collector formed by expanding, the corners of the electrode plate may be deformed due to interference with the manufacturing equipment during the electrode plate manufacturing process. When a lead-acid battery is manufactured using such electrode plates, the corners of the electrode plate are likely to break through the separator in the early stages, causing a short circuit. Because the separator of this embodiment has high strength, even when combined with an electrode plate using an expanded lattice, it can suppress early short circuits caused by deformation of the electrode plate. At least one of the positive electrode plate and the negative electrode plate may include an expanded lattice.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] Examples of the carbonaceous material in the negative electrode 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.

[0098] 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.

[0099] 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.

[0100] 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)).

[0101] 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.

[0102] The negative electrode active material in the charged state is sponge lead, but the unformed negative electrode plate is usually made using lead powder.

[0103] 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.

[0104] 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.

[0105] There is no particular limit to the number of positive and negative electrode plates contained in one cell. However, the separator of this embodiment is particularly suitable for use in lead-acid batteries in which a large number of positive and negative electrode plates are housed in one cell. When a total of 12 or more positive and negative electrode plates are housed in one cell, the tensile strength of the separator becomes particularly important.

[0106] (electrolyte) The electrolyte is an aqueous solution containing sulfuric acid, and may be gelled if necessary.

[0107] 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.

[0108] 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.

[0109] (1) Life performance The life performance (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 conducted 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 cold cranking current of 390A and record the voltage at the 30th second. Then, charge the battery as described in (b). These discharges and charges are also included in the life cycle (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 (hereinafter sometimes referred to as "number of cycles N") is used as an index of life performance. The rated cold cranking current 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.

[0110] (2) Tensile strength The tensile strength of a separator is measured using the following procedure. First, a test piece is obtained by cutting the separator into a size of 10 mm x 40 mm. A tensile test is performed on this test piece using a precision universal testing machine (Shimadzu Corporation, product name: AGS-X) with a chuck distance of 20 mm, a tensile speed of 5 mm / min, and at 25°C. The stress at break is taken as the tensile strength.

[0111] An example of a lead-acid battery according to this embodiment will be specifically described below with reference to the drawings. The components described above can be applied to the components of the lead-acid battery of the example described below. Furthermore, the components of the lead-acid battery of the example described below can be modified based on the above description. Furthermore, the matters described below may be applied to the above embodiment. Furthermore, in the embodiment described below, components that are not essential for the lead-acid battery according to this embodiment may be omitted.

[0112] 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 with 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 added. The vent plug 18 may have a function of venting gas generated in the cell chambers 14 to the outside of the battery.

[0113] Each electrode plate group 11 is formed by stacking multiple negative electrode plates 2 and multiple positive electrode plates 3 with separators 4 interposed between them. Here, a pouch-shaped separator 4 is shown housing the negative electrode plates 2, but the shape of the separator is not particularly limited. In a cell chamber 14 located at one end of the battery case 12, a negative electrode shelf 6 that connects multiple negative electrode plates 2 in parallel is connected to a through-connector 8, and a positive electrode shelf 5 that connects multiple 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 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.

[0114] The items described in this specification can be combined in any manner.

[0115] [Example] The present invention will be specifically described below based on examples, but the present invention is not limited to the following examples.

[0116] (Experimental Example 1) In Experimental Example 1, a plurality of separators and a plurality of lead-acid batteries were produced in the following procedure.

[0117] (1) Preparation and evaluation of separator The resin composition that comprises 100 mass parts of polyethylene, 160 mass parts of silica particles, 80 mass parts of paraffin oil as pore-forming agent, and 2 mass parts of penetrant is extruded into sheet, and then stretched, by removing part of pore-forming agent, prepare porous membrane with rib on one side.At this time, the cooling speed of extruded sheet and the stretching ratio are adjusted so that the ratio R of porous membrane that is obtained by the above-mentioned procedure is the value shown in Table 1.

[0118] Next, a carbon material was placed on one main surface (the main surface on the negative electrode plate side) of each of the formed porous films using the following procedure. First, a mixture of silica and carbon material was deposited on the separator, and then a pure carbon layer was deposited on top of that using roller coating or spray coating. In this way, the carbon material was placed. The thickness of the carbon material was the same for each porous film. Specifically, it was 10 μm. Using the above procedure, multiple separators with different porous film ratios R were produced.

[0119] 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 0.6 mm. The separator thickness (thickness of the base portion) determined by the above-mentioned procedure is shown in Table 1.

[0120] The separator sheet obtained by the above procedure was folded in half to form a bag with the ribs on the outer surface. The two overlapping ends were then crimped together to obtain a separator bag. The inner surface of the separator bag was the surface on which the carbon material was placed.

[0121] The ratio R of the porous membrane (F) in the separator, the oil content, the silica particle content, the separator thickness, and the rib height were measured for the separator before fabrication of the lead-acid battery. These values ​​were almost the same as those measured for the separator removed from the fabricated lead-acid battery using the above-mentioned procedure.

[0122] (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 a Pb-Ca-Sn alloy containing no antimony, and then aged and dried to obtain an unformed positive electrode plate measuring 100 mm wide, 110 mm high, and 1.6 mm thick.

[0123] (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 100 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.

[0124] (4) Preparation of lead-acid battery The unformed negative electrode plates were housed in a pouch-shaped separator and stacked with the positive electrode plates to form an electrode plate assembly consisting of seven unformed negative electrode plates and six unformed positive electrode plates.

[0125] The lugs of the positive and negative plates were welded to the positive and negative shelf sections, respectively, using the cast-on-strap (COS) 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 groups were connected in series inside the battery case.

[0126] The electrolyte used was an aqueous sulfuric acid solution, and the specific gravity of the electrolyte after formation at 20°C was 1.285.

[0127] The XRD spectrum of the porous membrane used in the separator of Battery A1, measured using the procedure described above, is shown in Figure 2. As shown in Figure 2, a 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 a 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°.

[0128] The life performance (number of cycles N) of the obtained lead-acid batteries was evaluated according to the procedure described above. The life performance was evaluated as a relative value of the number of cycles N of each lead-acid battery. The relative value of the number of cycles N is the value when the number of cycles N of battery CA1 is set to 90. The evaluation results are shown in Table 1. Batteries A1 to A4 are inventive examples, and battery CA1 is a comparative example.

[0129] [Table 1]

[0130] As shown in Table 1, when the ratio R of the porous membrane was 0.70 or higher, the life performance was significantly improved compared to when the ratio R was 0.65. This is thought to be because the high crystallinity of the porous membrane improved the oxidation resistance of the separator.

[0131] (Experimental Example 2) In Experimental Example 2, lead-acid batteries were fabricated and evaluated in the same manner as in Experimental Example 1, except that the separator was changed. Specifically, a plurality of separators were fabricated in the same manner as in Experimental Example 1, except that the manufacturing conditions were changed to change the porous membrane ratio R and the separator thickness. The carbon material was arranged under the same conditions as in the separator of Experimental Example 1.

[0132] The produced separators and lead-acid batteries were evaluated in the same manner as in Experimental Example 1. The evaluation results are shown in Table 2. Batteries B1 to B12 are invention examples, and batteries CB1 to CB4 are comparative examples. The life performance (number of cycles N) in Table 2 is a relative value when the number of cycles N of battery B1 is set to 100.

[0133] [Table 2]

[0134] As shown in Table 2, by increasing the separator thickness to 100 μm or more, we were able to significantly improve the lifespan performance. If the separator is thin (if the porous membrane is thin), the resin does not flow well into the mold during resin molding to form the porous membrane, which is thought to result in large variations in thickness and pore size, and partial cracking (separator tears). On the other hand, if the separator is 100 μm or thicker (porous membrane thickness is 90 μm or thicker), the resin flows better, resulting in a homogeneous porous membrane. In addition, by placing a carbon material on the surface of the porous membrane, the tensile strength of the separator is significantly improved, as described below. This is thought to be the reason for the significant improvement in lifespan characteristics.

[0135] (Experimental Example 3) In Experimental Example 3, multiple separators were produced under different production conditions. Specifically, multiple separators were produced using the same method as in Experimental Example 1, except that the production conditions were changed to vary the porous membrane ratio R and the separator thickness, and the presence or absence of a carbon material was changed. The produced separators were evaluated in the same manner as in Experimental Example 1.

[0136] Furthermore, the tensile strength of the produced separators was measured using the method described above. The evaluation results of the separators are shown in Tables 3 and 4. Separators S1 to S10 are separators of the invention, and separators CS1 to CS12 are separators of comparative examples. The tensile strength is a relative value when the tensile strength of separator CS1 is set to 100.

[0137] [Table 3]

[0138] [Table 4]

[0139] The results of Table 3 are shown in Figure 3, and the results of Table 4 are shown in Figure 4. As shown in Table 3 and Figure 3, by placing a carbon material on the surface and setting the porous membrane ratio R to 0.70 or more, the tensile strength of the separator could be significantly increased. As shown in Table 4 and Figure 4, by placing a carbon material on the surface and setting the thickness to 100 μm or more, the tensile strength of the separator could be significantly increased.

[0140] As shown in Figure 3, the effect of increasing the ratio R on the tensile strength of the separator with the carbon material disposed therein was greater than that of the separator without the carbon material disposed therein. As shown in Figure 4, the effect of increasing the tensile strength of the separator with the carbon material disposed therein by increasing the separator thickness was greater than that of the separator without the carbon material disposed therein. The reasons for this are not clear, but it is thought that disposing the carbon material on the surface of the porous membrane has some kind of synergistic effect. [Industrial Applicability]

[0141] The present invention can be used for lead-acid batteries and separators used therein. The lead-acid battery separator of the present invention is suitable for, for example, IS applications (such as lead-acid batteries for ISS vehicles) and starting power sources 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 uses are merely examples. The uses of the lead-acid battery separator and lead-acid battery of the present invention are not limited to these. [Explanation of symbols]

[0142] 1: lead-acid battery, 2: negative electrode plate, 3: positive electrode plate, 4: separator, 5: positive electrode shelf, 6: negative electrode shelf, 7: positive electrode column, 8: through-connector, 9: negative electrode column, 11: electrode plate group, 12: battery case, 13: partition wall, 14: cell chamber, 15: lid, 16: negative electrode terminal, 17: positive electrode terminal, 18: liquid vent plug

Claims

1. A separator for a lead-acid battery, a porous membrane containing polyolefin and a carbon material disposed on a surface of the porous membrane, the porous film includes a crystalline region and an amorphous region; In the X-ray diffraction spectrum of the porous film, A １ / (A １ +A ２ ) is 0.70 or more, A １ is the area of ​​the first diffraction peak having the largest peak height among the diffraction peaks corresponding to the crystalline region, A ２ is the area of ​​the second diffraction peak having the second highest peak height among the diffraction peaks corresponding to the crystalline region, The polyolefin contains at least ethylene units, the first diffraction peak corresponds to the (110) plane of the crystalline region; The separator for a lead-acid battery, wherein the second diffraction peak corresponds to the (200) plane of the crystalline region.

2. 2. The separator for a lead-acid battery according to claim 1, having a thickness of 100 μm or more and 300 μm or less.

3. 3. The separator for a lead acid battery according to claim 1, wherein the ratio R is 0.90 or less.

4. The separator for a lead acid battery according to any one of claims 1 to 3, containing oil.

5. The separator for a lead acid battery according to any one of claims 1 to 4, wherein the tortuosity of the pores of the porous film is 5 or more.

6. The lead-acid battery separator according to any one of claims 1 to 5, wherein the carbon material is at least one selected from the group consisting of conductive carbon black and conductive carbon fiber.

7. 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, A lead-acid battery, wherein the separator is the lead-acid battery separator according to any one of claims 1 to 6.

8. The lead-acid battery according to claim 7 , wherein the carbon material of the separator is disposed on one of two main surfaces of the porous membrane that is closer to the negative electrode plate.

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