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

Abstract

To provide a separator for a lead-acid battery capable of contributing to improvement in life performance and productivity.SOLUTION: A separator for a lead-acid battery includes a porous film and a carbon material arranged 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 crystallinity represented by 100×Ic / (Ic+Ia) is 20% or more, where Ic is an integration intensity of a diffraction peak with the maximum peak height, among diffraction peaks corresponding to the crystalline region, and Ia is the integration 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 Art

[0002] Lead-acid batteries are used in various applications, including in-vehicle and industrial applications. A lead-acid battery includes a positive electrode plate, a negative electrode plate, a separator interposed therebetween, and an electrolytic solution. Various performances are required for the separator of a lead-acid battery.

[0003] Patent Document 1 discloses "a ribbed separator for a lead-acid battery obtained by heating and melting a raw material composition composed of a mixture of 20 to 60% by mass of a polyolefin resin, 80 to 40% by mass of an inorganic powder, and 40 to 240% by mass of a mineral oil with respect to these blends, molding it into a sheet shape having ribs while kneading, then immersing it in a dipping tank of an organic solvent capable of dissolving the oil to extract and remove a part of the oil, and heating and drying it, wherein the difference in the oil content between the rib portion and the base portion of the separator is 5% by mass or less."

[0004] Patent Document 2 discloses "a lead-acid battery separator comprising a porous membrane and / or a fibrous mat, and one or more conductive elements or nucleation additive(s) inside or on top of the porous membrane and / or the fibrous mat."

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] For current lead-acid batteries such as those for idling stop vehicles, performance under usage conditions different from those of past lead-acid batteries is required. Among these, there has always been a demand to improve the life performance of lead-acid batteries and to improve productivity. Therefore, new technologies that can contribute to improving life performance and productivity are required.

Means for Solving the Problems

[0007] One aspect of the present disclosure relates to a separator for a lead-acid battery. The separator for a lead-acid battery includes a porous membrane and a carbon material disposed on the surface of the porous membrane. The porous membrane includes a crystalline region and an amorphous region. In the X-ray diffraction spectrum of the porous membrane, the crystallinity represented by 100×I c / (I c +I a ) is 20% or more, where I c is the integrated intensity of the diffraction peak with the maximum peak height among the diffraction peaks corresponding to the crystalline region, and I a is the integrated intensity of the halo corresponding to the amorphous region.

[0008] Another aspect of the present disclosure relates to a lead-acid battery. The lead-acid battery includes at least one cell including a plate group and an electrolyte. The 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 the separator for a lead-acid battery of the above aspect.

Advantages of the Invention

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

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Mode for Carrying Out the Invention

[0011] Hereinafter, 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 can be obtained. In this specification, the description “numerical value A to numerical value B” includes the numerical value A and the numerical value B, and can be read as “numerical value A or more and numerical value B or less”. In the following description, when the lower limit and the upper limit are exemplified for numerical values such as specific physical properties and conditions, any combination of any of the exemplified lower limits and any of the exemplified upper limits can be made as long as the lower limit is not more than the upper limit.

[0012] (Separator for Lead-Acid Batteries) The separator for lead-acid batteries according to one aspect of the present invention includes a porous membrane and a carbon material disposed on the surface of the porous membrane. The porous membrane may be hereinafter referred to as “porous membrane (F)”. The porous membrane (F) includes a crystalline region and an amorphous region. In the X-ray diffraction spectrum of the porous membrane (F), the crystallinity represented by 100×I c / (I c +I a ) is 20% or more. I c is the integrated intensity of the diffraction peak having the maximum peak height among the diffraction peaks corresponding to the crystalline region (hereinafter sometimes referred to as the “first diffraction peak”). I a is the integrated intensity of the halo corresponding to the amorphous region.

[0013] Lead-acid batteries may be used under harsh conditions. One of the typical applications of lead-acid batteries is automotive use. In recent years, due to automobiles being caught in traffic jams or constantly used like commercial vehicles, the chances of lead-acid batteries being exposed to overcharged states have increased. Also, with global warming, the opportunities for lead-acid batteries to be used in higher temperature environments during summer have increased. Therefore, in recent years, lead-acid batteries are increasingly being required to have an even higher level of life performance (e.g., high-temperature overcharge life performance) compared to the past.

[0014] One of the factors shortening the life of lead-acid batteries is the oxidative degradation of the separator. When ribs are provided on the surface of the separator facing the positive electrode plate, a gap is formed between the separator and the positive electrode plate. Therefore, providing ribs tends to reduce the oxidative degradation of the separator. However, with the improvement of the performance of lead-acid batteries, compared to the past, it has become more common to accommodate a large number of thin electrode plates per cell. Therefore, simply providing ribs is insufficient to suppress the oxidative degradation of the separator. Even when the separator contains oil, the oxidative degradation of the separator can be reduced to some extent. However, since the insulating oil blocks the pores of the separator, the resistance of the separator increases, and the reactivity of the electrode plate tends to decrease. Therefore, it is difficult to increase the oil content rate in the separator in high-performance lead-acid batteries. Thus, it is difficult for conventional separators to improve the life performance of lead-acid batteries to a high level.

[0015] Since the crystallinity of the porous membrane (F) of the present embodiment is 20% or more, the oxidation resistance of the porous membrane (F) is high. Unlike the case of enhancing oxidation resistance with oil, when enhancing oxidation resistance by crystallinity, there are almost no demerits such as an increase in resistance. Therefore, excellent life performance can be ensured even in high-performance lead-acid batteries.

[0016] The separator for a lead-acid battery has a relatively large thickness, which is different from separators for lithium-ion secondary batteries and the like. Also, in a lead-acid battery, compared to a lithium-ion secondary battery, the positive electrode potential during overcharge is low, so sufficient oxidation resistance could be ensured by ribs, oil, etc. in the conventional usage environment or usage form. In addition, as the thickness of the separator increases, it becomes more difficult to increase the crystallinity. Moreover, when the crystallinity increases, the separator tends to become hard and brittle. From such a perspective, conventionally, the crystallinity of the separator for a lead-acid battery has not been controlled. The crystallinity of the conventional separator for a lead-acid battery was about 18% or less, which was relatively low. Against such conventional common sense, in this embodiment, the crystallinity of the porous membrane (F) is set to 20% or more. Thereby, the life performance (for example, high-temperature overcharge life performance) can be greatly improved.

[0017] Also, the life of a lead-acid battery is significantly reduced due to non-uniformity (stratification) of the concentration of the electrolyte. In a lead-acid battery, the concentration of the electrolyte at the upper part of the battery may be lower than that at the lower part, thereby degrading the life performance of the battery.

[0018] The separator of this embodiment contains a carbon material disposed on the surface. Since this carbon material comes into contact with the electrode (positive electrode or negative electrode) in the lead-acid battery, it is electrically connected to the electrode. As a result, when the lead-acid battery is charged (for example, at the end of charging), water can be electrolyzed by the carbon material to generate gas. Since the generated gas stirs the electrolyte, stratification of the electrolyte is suppressed.

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

[0020] In addition, in lead-acid batteries, performance improvement is being promoted by using a large number of thin plates. In lead-acid batteries using a large number of thin plates, the defect occurrence rate during manufacturing increases due to insufficient strength of the separator. Therefore, increasing the strength of the separator is particularly important for improving the reliability and productivity of high-performance lead-acid batteries.

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

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

[0023] The crystallinity of the porous film (F) is preferably 40% or less. In this case, in addition to easily ensuring the flexibility of the separator, the manufacturing is easy.

[0024] The separator (or the porous film (F)) preferably contains oil. In this case, the effect of suppressing oxidative degradation of the separator is further enhanced, and higher life performance can be ensured.

[0025] The porous film (F) preferably contains a polyolefin, and more preferably contains a polyolefin containing at least an ethylene unit. Such a separator is easily oxidatively degraded, but the crystallinity can be relatively easily increased. When the porous film (F) contains a polyolefin containing at least an ethylene unit, the first diffraction peak corresponds to the (110) plane of the crystalline region.

[0026] (Carbon material) As the carbon material, a carbon material having conductivity can be used. Examples of the carbon material having conductivity include graphite, activated carbon, carbon black, carbon fiber, carbon nanotube, and the like. Examples of the conductive carbon black include acetylene black, ketjen black, high surface area carbon black, and the like. From the viewpoint of productivity, it is preferable to use carbon black. 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 layers on the surface of the porous membrane (F). The method of arranging the carbon material will be described later.

[0027] The carbon material may be arranged only on 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 may be arranged on both main surfaces. In other words, the carbon material exists on at least one surface of the separator. In a preferred example, the carbon material is arranged only on one main surface of the porous membrane (F). As will be described later, the carbon material may be arranged only on the main surface of the porous membrane (F) on the negative electrode plate side.

[0028] The carbon material may be arranged in layers so as to cover the main surface of the porous membrane (F), or may be arranged in a non-layered form. Examples of the non-layered form include a form in which the carbon material is arranged in dispersed island-like shapes. The thickness of the layer of the carbon material 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 layer of the carbon material can be measured in the same manner as the thickness of the separator.

[0029] The content of the carbon material in the separator (the carbon material arranged on the surface of the porous membrane (F)) may be 2% by mass or more, preferably 3% by mass or more. By setting the content to 2% by mass or more, it is possible to particularly enhance the oxidation resistance and strength of the separator. The content may be 40% by mass or less, or 30% by mass or less.

[0030] (porous membrane (F)) The porous membrane (F) includes a crystalline region in which the molecules of the constituent material of the porous membrane (F) are arranged relatively regularly (i.e., high degree of alignment), and an amorphous region with a low degree of alignment. Therefore, in the XRD spectrum of the porous membrane (F), diffraction peaks due to the crystalline region are observed, and scattered light due to the amorphous region is observed as a halo. In the XRD spectrum of the porous membrane (F), when the crystallinity represented by 100×I c / (I c +I a ) is 20% or more, excellent life performance can be obtained. Here, I c is the integrated intensity of the diffraction peak with the maximum peak height among the diffraction peaks corresponding to the crystalline region (the first diffraction peak), and I a is the integrated intensity of the halo corresponding to the amorphous region.

[0031] For example, in the XRD spectrum of the porous membrane (F) containing a polyolefin containing ethylene units, the diffraction peak corresponding to the (110) plane of the crystalline region is observed in the range where 2θ is 20° or more and 22.5° or less, and the diffraction peak corresponding to the (200) plane of the crystalline region is observed in the range where 2θ is 23° or more and 24.5° or less. Also, the halo of the amorphous region is observed in the range where 2θ is 17° or more and 27° or less. Among the diffraction peaks due to the crystalline region, the diffraction peak corresponding to the (110) plane has the maximum peak height and corresponds to the first diffraction peak.

[0032] The crystallinity is 20% or more, and from the viewpoint of ensuring higher life performance, it may be 23% or more or 25% or more. The crystallinity may be 40% or less, 35% or less, or 30% or less. When the crystallinity is in such a range, in addition to being easy to ensure the flexibility of the separator, the manufacturing is easy.

[0033] The crystallinity of the porous membrane (F) may be 20% or more and 40% or less, 20% or more and 35% or less, or 20% or more and 30% or less. In these ranges, the lower limit value may be 23% or more or 25% or more.

[0034] The integrated intensities of the diffraction peaks and the 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 membrane (F). The integrated intensity I c of the first diffraction peak and the integrated intensity I a of the halo are used to determine the crystallinity from the above formula.

[0035] The porous membrane (F) contains a polymer material (hereinafter also referred to as the 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 olefin units (that is, a polymer containing at least monomer units derived from olefins).

[0036] As the base polymer, a polyolefin and another base polymer may be used in combination. The ratio of the polyolefin in the total base polymer contained in the porous membrane (F) is, for example, 50% by mass or more, may be 80% by mass or more, and may be 90% by mass or more. The ratio of the polyolefin is, for example, 100% by mass or less. The base polymer may be composed of only polyolefin. When the ratio of the polyolefin is thus large, the oxidation resistance of the porous membrane (F) tends to be low. However, even in such a case, high life performance can be ensured by setting the crystallinity within the above range.

[0037] The polyolefin includes, for example, a homopolymer of an olefin, a copolymer containing different olefin units, and a copolymer containing olefin units and copolymerizable monomer units. The copolymer containing olefin units and copolymerizable monomer units may contain one or more kinds of olefin units. Also, the copolymer containing olefin units and copolymerizable monomer units may contain one or more kinds of copolymerizable monomer units. The copolymerizable monomer unit is a monomer unit derived from a polymerizable monomer other than an olefin and copolymerizable with an olefin.

[0038] Examples of polyolefins include polymers containing at least C 2-3 olefins as monomer units. C 2-3 Examples of olefins include at least one selected from the group consisting of ethylene and propylene. Examples of polyolefins include polyethylene, polypropylene, C 2-3 Copolymers containing olefins as monomer units (e.g., ethylene-propylene copolymers) are more preferred. Among polyolefins, it is preferable to use polyolefins containing at least ethylene units (such as polyethylene and ethylene-propylene copolymers). It is also possible to use a combination of polyolefins containing ethylene units (such as polyethylene and ethylene-propylene copolymers) and other polyolefins.

[0039] The separator (more specifically, the porous membrane (F)) preferably contains oil. When the separator contains oil, the effect of suppressing the oxidative degradation of the separator can be further enhanced, so that higher life performance can be ensured. 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 derived oils, mineral oils, and synthetic oils. As oils, mineral oils, synthetic oils, etc. are preferable. Examples of oils include paraffin oil and silicone oil. The separator may contain one kind of oil or a combination of two or more kinds.

[0040] The oil content in the separator is preferably 11% by mass or more and 18% by mass or less. When the oil content is within such a range, the effect of suppressing the oxidative degradation of the separator is further enhanced. Also, the resistance of the separator can be kept relatively low.

[0041] The separator may be in the form of a sheet. Also, a sheet bent in a bellows shape may be used as the separator. The separator may be formed in a bag shape. Either the positive electrode plate or the negative electrode plate may be wrapped in a bag-shaped separator.

[0042] The separator may or may not have ribs. The separator having ribs includes, for example, a base portion and ribs standing upright from the surface of the base portion. The ribs may be provided on only one surface of the separator or each base portion, or may be provided on both surfaces respectively. Note that the base portion of the separator refers to the portion excluding protrusions such as ribs among the constituent parts of the separator, and is a sheet-like portion defining the outer shape of the separator.

[0043] The thickness of the separator is 100 μm or more. From the viewpoint of obtaining 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 at the portion facing the electrode material of the separator. When the separator includes ribs standing upright from at least one surface of the base portion, the thickness of the separator is the average thickness at the base portion. When an attachment member (such as a mat or a pasting paper) is attached to the separator, the thickness of the attachment member is not included in the thickness of the separator.

[0044] 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. The lower limit of these ranges may be 120 μm or more, or 150 μm or more.

[0045] When the separator has ribs, the height of the ribs may be 0.05 mm or more. Also, the height of the ribs may be 1.2 mm or less. The height of the ribs is the height of the portion protruding from the surface of the base portion (protrusion height).

[0046] The height of the ribs provided in the region of the separator facing the positive electrode plate may be 0.4 mm or more. The height of the ribs provided in the region of the separator facing the positive electrode plate may be 1.2 mm or less.

[0047] The carbon material is disposed on the surface of the formed porous membrane (F). There is no particular limitation on the method of disposing the carbon material. For example, the carbon material may be formed by applying a carbon material, a composition containing the carbon material, or a dispersion containing the carbon material onto the surface of the porous membrane (F). There is no particular limitation on the coating method, and a doctor blade method, a roller coating method, a spray coating method, a dipping method, a vapor deposition method, or other printing methods may be used. Examples of the dispersion containing the carbon material include a dispersion in which the 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 the carbon material to be applied.

[0048] The porous membrane (F) is obtained, for example, by extruding a resin composition containing a base polymer, a pore former, and a penetrant (surfactant) into a sheet shape, performing a stretching treatment, and then removing at least a part of the pore former. By removing at least a part of the pore former, fine pores are formed in the matrix of the base polymer. The sheet-shaped porous membrane (F) is dried as necessary after removing the pore former. For example, the crystallinity is adjusted by adjusting at least one selected from the group consisting of the cooling rate of the sheet during extrusion molding, the stretching ratio during the stretching treatment, and the temperature during the drying treatment. For example, when the sheet is rapidly cooled during extrusion molding, the stretching ratio is increased, or the temperature during the drying treatment is lowered, the crystallinity tends to increase. The stretching treatment may be performed by biaxial stretching, but is usually performed by uniaxial stretching. The sheet-shaped separator may be bent in a bellows shape or processed into a bag shape as necessary. When a separator having the carbon material disposed only on 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.

[0049] In a separator having ribs, the ribs may be formed when the resin composition is extruded into a sheet shape. Further, the ribs may be formed by pressing the sheet with a roller having grooves corresponding to each rib after the resin composition is formed into a sheet shape 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 separator containing oil can be obtained, and the effect of suppressing oxidative degradation is further enhanced. The pore-forming agent may be used alone or in combination of two or more kinds. Oil and other pore-forming agents may be used in combination. A liquid pore-forming agent and a solid pore-forming agent may be used in combination. Here, at room temperature (a temperature of 20°C or higher and 35°C or lower), a liquid pore-forming agent is classified as a liquid pore-forming agent, and a solid pore-forming agent is classified as a solid pore-forming agent.

[0051] As the liquid pore-forming agent, the above-described oil is preferable. Examples of the solid pore-forming agent include polymer powder.

[0052] The amount of the pore-forming agent in the porous membrane (F) may vary depending on the type of the 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.

[0053] For example, a porous membrane (F) containing oil is formed by extracting and removing a part of the oil from a sheet formed using oil as the pore-forming agent with a solvent. The solvent is selected according to, for example, the type of the oil. For example, by adjusting the type and composition of the solvent, extraction conditions (extraction time, extraction temperature, rate of supplying the solvent, etc.), the oil content in the porous membrane (F) is adjusted.

[0054] Examples of the surfactant as the penetrant include either an ionic surfactant or a nonionic surfactant. The surfactant may be used alone or in combination of two or more kinds.

[0055] The content rate 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. The content rate of the penetrant in the porous membrane (F) may be 10% by mass or less.

[0056] The porous membrane (F) (or the resin composition used for producing the porous membrane (F)) may contain inorganic particles. Note that the carbon material disposed on the surface of the porous membrane (F) is not included in the inorganic particles.

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

[0058] The content rate of the inorganic particles other than the carbon material in the porous membrane (F) may be, for example, 40% by mass or more. The content rate of the inorganic particles is, for example, 80% by mass or less, and may be 70% by mass or less.

[0059] (Analysis or size measurement of the separator) (Preparation of the separator) For the analysis or size measurement of the separator, an unused separator or a separator taken out from a fully charged lead storage battery at the initial stage of use is used. The separator taken out from the lead storage battery is washed and dried prior to the analysis or measurement. Note that the measurement of the XRD spectrum of the porous membrane (F) may be performed using the porous membrane (F) before disposing the carbon material on the surface. Also, the measurement of the XRD spectrum of the porous membrane (F) having the carbon material disposed only on one side may be performed using the surface on the side where the carbon material is not disposed.

[0060] The cleaning and drying of the separator taken out from the lead-acid battery are performed according to the following procedure. The separator taken out from the lead-acid battery is immersed in pure water for 1 hour to remove sulfuric acid in the separator. Then, the separator is taken out from the immersed liquid and left to stand for 16 hours or more in an environment of 25°C ± 5°C to be dried. For the separator with carbon materials arranged on both sides, after removing the carbon materials by polishing, the XRD spectrum is measured.

[0061] In this specification, the fully charged state of the lead-acid battery is defined according to JIS D 5301:2019. More specifically, in a water tank of 25°C ± 2°C, the lead-acid battery is charged with a current (A) that is 1 / 10 of the numerical value described as the rated capacity, and the terminal voltage (V) during charging measured every 15 minutes or the electrolyte density converted to 20°C is continuously measured three times until it shows a constant value with three significant figures. The state of being charged until then is the fully charged state. The numerical value described as the rated capacity is a numerical value with the unit of Ah (ampere-hour). The unit of the current set based on the numerical value described as the rated capacity is A (ampere).

[0062] The fully charged lead-acid battery is a lead-acid battery obtained by fully charging a preformed lead-acid battery. The full charge of the lead-acid battery may be immediately after formation if it is after formation, or may be performed after a lapse of time from formation (for example, after formation, a lead-acid battery during use (preferably in the initial stage of use) may be fully charged).

[0063] In this specification, the battery in the initial stage of use is a battery that has not elapsed much time since the start of use and has hardly deteriorated.

[0064] (XRD spectrum) The XRD spectrum of the porous membrane (F) is measured by irradiating X-rays from a direction perpendicular to the surface of the porous membrane (F). The sample for measurement is prepared by processing the portion of the porous membrane (F) facing the electrode material into a strip shape. For the porous membrane (F) having ribs, the sample is prepared by processing the base portion into a strip shape so as not to include the ribs. The measurement and fitting of the XRD spectrum are performed under the following measurement conditions.

[0065] (Measurement conditions) Measuring 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: Use XRD pattern analysis software (PDXL2, manufactured by Rigaku).

[0066] (Thickness of separator and height of rib) The thickness of the separator is obtained by measuring the thickness at arbitrarily selected 5 locations in the cross-sectional photograph of the separator and averaging. When the carbon material is layered, the thickness of the carbon material layer is obtained by the same method.

[0067] The height of the rib is obtained by the following procedure. First, arbitrarily select 10 locations of the rib in the cross-sectional photograph of the separator. Next, measure the height of the rib (height from the surface of the base part) at each of the selected 10 locations. Next, the height of the rib is obtained by averaging the measured heights of the 10 locations.

[0068] (Oil content in the porous membrane (F)) The part of the separator facing the electrode material is processed into a strip shape 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 a separator having ribs, sample A is prepared by processing the base part into a strip shape so as not to include the ribs.

[0069] Collect approximately 0.5 g of Sample A, accurately weigh it, and determine the mass (m0) of the initial sample. Place the weighed Sample A in a glass beaker of appropriate size and add 50 mL of n - hexane. Then, apply ultrasonic waves to the beaker containing the sample for approximately 30 minutes to elute the oil content in Sample A into the n - hexane. Next, take out the sample from the n - hexane, dry it in the air at room temperature (a temperature between 20°C and 35°C), and then weigh it to determine the mass (m1) of the sample after oil removal. Then, calculate the oil content using the following formula. Determine the oil content for 10 samples of Sample A and calculate the average value. Take the obtained average value as the oil content in the porous membrane (F). Oil content (mass %) = 100×(m0 - m1) / m0

[0070] (Content of inorganic particles in the porous membrane (F)) Collect a part of Sample A prepared in the same manner as above, accurately weigh it, then place it in a platinum crucible and heat it with a Bunsen burner until no white smoke emerges. Next, heat the obtained sample in an electric furnace (in an oxygen stream, 550°C ± 10°C) for approximately 1 hour to incinerate it, and weigh the ash. Calculate the ratio (percentage) of the mass of the ash to the mass of Sample A, and take it as the content of the above - mentioned inorganic particles (mass %). Determine the content of inorganic particles for 10 samples of Sample A and calculate the average value. Take the obtained average value as the content of inorganic particles (inorganic particles other than carbon materials) in the porous membrane (F).

[0071] (Content of penetrant in the porous membrane (F)) Take a part of Sample A prepared in the same manner as described above, accurately weigh it, and then dry it for 12 hours or more at room temperature (a temperature of 20°C or higher and 35°C or lower) under a reduced pressure environment lower than atmospheric pressure. Put the dried product into a platinum cell, set it in a thermogravimetric analyzer, and raise the temperature from room temperature to 800°C ± 1°C at a heating rate of 10 K / min. The mass reduction amount when the temperature is raised from room temperature to 250°C ± 1°C is taken as the mass of the penetrant, and the ratio (percentage) of the mass of the penetrant in the mass of Sample B is calculated and used as the content rate (mass %) of the above penetrant. As the thermogravimetric analyzer, Q5000IR manufactured by T.A. Instruments is used. Determine the content rate of the penetrant for 10 samples of Sample A and calculate the average value. The obtained average value is used as the content rate of the penetrant in the porous membrane (F).

[0072] (Lead-acid battery) The lead-acid battery according to one aspect of the present invention includes at least one cell including a plate group and an electrolyte. The 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 separator for a lead-acid battery according to the present embodiment. By using the separator of the present embodiment, the life performance and productivity of the lead-acid battery can be significantly improved.

[0073] The lead-acid battery may be a valve-regulated battery (VRLA battery), but a liquid battery (vented battery) is preferred.

[0074] The carbon material of the separator may be arranged on both main surfaces of the porous membrane (F), or may be arranged 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 arranged on the main surface on the negative electrode plate side of the two main surfaces of the porous membrane (F). When electrolysis of water occurs during charging, oxygen gas is generated on the positive electrode side. By arranging the carbon material on the negative electrode plate side, it is possible to suppress the generation of oxygen gas in the separator and the oxidation of the porous membrane (F).

[0075] In this specification, the vertical direction of a lead-acid battery or its components (such as electrode plates, battery cases, separators, etc.) means the vertical up-and-down direction of the lead-acid battery when it is in use. Each of the positive and negative electrode plates has an ear for connecting to an external terminal. In a flooded battery, the ear is provided at the upper part of the electrode plate so as to protrude upward. Examples of the components of the lead-acid battery will be described below.

[0076] (Positive electrode plate) As the positive electrode plate, a pasted positive electrode plate is used. The pasted positive electrode plate includes a positive current collector and a positive electrode material. The positive electrode material is held by the positive current collector. The positive electrode material is the part of the positive electrode plate excluding the positive current collector. Note that members such as mats and pasting papers may be attached to the electrode plate. Since such members (also referred to as attached members) are used integrally with the electrode plate, they are included in the electrode plate. When the positive electrode plate includes an attached member, the positive electrode material is the part of the positive electrode plate excluding the positive current collector and the attached member.

[0077] The positive current collector included in the positive electrode plate may be formed by casting lead (Pb) or a lead alloy, or may be formed by processing a lead or lead alloy sheet. Examples of the processing method include expansion processing or punching processing. It is preferable to use a lattice-shaped current collector as the positive current collector because it is easy to carry the positive electrode material.

[0078] As the lead alloy used for the positive current collector, Pb-Ca-based alloys and Pb-Ca-Sn-based alloys are preferable in terms of corrosion resistance and mechanical strength. The positive current collector may have lead alloy layers with different compositions, and the alloy layer may be one layer or multiple layers.

[0079] The positive electrode material included in the positive electrode plate contains a positive active material (lead dioxide or lead sulfate) that exhibits capacitance through an oxidation-reduction reaction. The positive electrode material may contain other additives (such as reinforcing materials) as required.

[0080] Examples of the reinforcing material include fibers (such as inorganic fibers and organic fibers). Examples of the resin (or polymer) constituting the organic fiber include at least one selected from the group consisting of acrylic resins, polyolefin resins (such as polypropylene resins and polyethylene resins), polyester resins (including polyalkylene arylates (such as polyethylene terephthalate)), and celluloses (such as cellulose and cellulose derivatives (such as cellulose ethers and cellulose esters)). Rayon is also included in the celluloses.

[0081] The content of the reinforcing material in the positive electrode material is, for example, 0.03% by mass or more. Also, the content of the reinforcing material in the positive electrode material is, for example, 0.5% by mass or less.

[0082] The unformed paste-type positive electrode plate is obtained by filling a positive electrode current collector with a positive electrode paste and aging and drying it. The positive electrode paste is prepared by adding water and sulfuric acid to lead powder, an antimony compound, and, if necessary, other additives (such as a reinforcing material) and kneading them.

[0083] A positive electrode plate is obtained by forming the unformed positive electrode plate. The forming can be performed by charging a group of electrode plates including the unformed positive electrode plate while the group of electrode plates is immersed in an electrolyte containing sulfuric acid in the battery case of a lead-acid battery. However, the forming may be performed before assembling the lead-acid battery or the group of electrode plates.

[0084] (Negative electrode 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 part of the negative electrode plate excluding the negative electrode current collector. Note that, in some cases, the above-described attachment member is attached to the negative electrode plate. In this case, the attachment member is included in the negative electrode plate. When the negative electrode plate includes the attachment member, the negative electrode material is the part of the negative electrode plate excluding the negative electrode current collector and the attachment member.

[0085] 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 expansion processing. In the electrode plate using a current collector formed by expansion processing, in the manufacturing process of the electrode plate, the corners of the electrode plate may be deformed due to interference with the manufacturing apparatus. When a lead storage battery is manufactured using such an electrode plate, at the initial stage, the corners of the electrode plate are likely to break through the separator and cause a short circuit. Since the separator of the present embodiment has high strength, even when combined with an electrode plate using an expanded lattice, an initial short circuit due to deformation of the electrode plate can be suppressed. At least one of the positive electrode plate and the negative electrode plate may contain an expanded lattice.

[0086] The lead alloy used for the negative electrode current collector may be any of a Pb-Sb based alloy, a Pb-Ca based alloy, and a Pb-Ca-Sn based alloy. These leads or lead alloys may further contain at least one selected from the group consisting of Ba, Ag, Al, Bi, As, Se, Cu, etc. as an additive element. The negative electrode current collector may have lead alloy layers with different compositions, and the alloy layer may be one layer or a plurality of layers.

[0087] The negative electrode material contained in the negative electrode plate contains a negative electrode active material (lead or lead sulfate) that exhibits capacitance by an oxidation-reduction reaction, and may contain an organic anti-shrinkage agent, a carbonaceous material, barium sulfate, etc. The negative electrode material may contain other additives (such as a reinforcing material) as necessary.

[0088] Examples of the organic anti-shrinkage agent include lignin, lignin sulfonic acid, synthetic organic anti-shrinkage agents (such as formaldehyde condensates of phenolic compounds). The negative electrode material may contain one kind of organic anti-shrinkage agent or two or more kinds.

[0089] The content rate of the organic anti-shrinkage agent in the negative electrode material is, for example, 0.01 mass% or more. The content rate of the organic anti-shrinkage agent is, for example, 1 mass% or less.

[0090] Examples of the carbonaceous material in the negative electrode material include carbon black, graphite (artificial graphite, natural graphite, etc.), hard carbon, soft carbon, and the like. The negative electrode material may contain one type of carbonaceous material or two or more types of carbonaceous materials.

[0091] The content rate of the carbonaceous material in the negative electrode material is, for example, 0.1% by mass or more. The content rate of the carbonaceous material may be, for example, 3% by mass or less.

[0092] The content rate of barium sulfate in the negative electrode material is, for example, 0.1% by mass or more. The content rate of barium sulfate is, for example, 3% by mass or less.

[0093] Examples of the reinforcing material include fibers (inorganic fibers, organic fibers (such as organic fibers composed of the resin described for the reinforcing material of the positive electrode material), etc.).

[0094] The content rate of the reinforcing material in the negative electrode material is, for example, 0.03% by mass or more. Also, the content rate of the reinforcing material in the negative electrode material is, for example, 0.5% by mass or less.

[0095] The negative electrode active material in the charged state is spongy lead, but the unformed negative electrode plate is usually produced using lead powder.

[0096] The negative electrode plate can be formed by filling a negative electrode current collector with a negative electrode paste, aging and drying it to produce an unformed negative electrode plate, and then subjecting the unformed negative electrode plate to formation. The negative electrode paste is produced by adding water and sulfuric acid to lead powder, an organic anti-shrinkage agent, and various additives as required and kneading them. In the aging process, it is preferable to age the unformed negative electrode plate at a temperature higher than room temperature and high humidity.

[0097] Formation can be performed by charging the electrode plate group including the unformed negative electrode plate in a state where the electrode plate group is immersed in the electrolyte containing sulfuric acid in the battery case of the lead storage battery. However, formation may be performed before the assembly of the lead storage battery or the electrode plate group. Spongy lead is generated by formation.

[0098] There is no particular limitation on the number of positive and negative plates included in one cell. However, the separator of the present embodiment is particularly preferably used for a lead storage battery in which a large number of positive and negative plates are housed in one cell. When a total of 12 or more positive and negative plates are housed in one cell, the tensile strength of the separator becomes particularly important.

[0099] (Electrolyte solution) The electrolyte solution is an aqueous solution containing sulfuric acid. The electrolyte solution may be gelled as necessary.

[0100] The electrolyte solution may further contain at least one kind of metal ion selected from the group consisting of Na ions, Li ions, Mg ions, and Al ions.

[0101] The specific gravity of the electrolyte solution at 20 °C is, for example, 1.10 or more. The specific gravity of the electrolyte solution at 20 °C may be 1.35 or less. Note that these specific gravities are values for the electrolyte solution of a fully charged lead storage battery.

[0102] (1) Life performance The life performance (high-temperature overcharge life performance) of the lead storage battery is evaluated based on the life of the lead storage battery when a high-temperature overcharge durability test is performed according to the following procedure. (a) Throughout the entire test period, place the storage battery in an air bath at 75 °C ± 3 °C. (b) Connect the storage battery to a life test device and continuously repeat the following discharge and charge cycles. One cycle of this discharge and charge is defined as one life (1 cycle). Discharge: Discharge current 25.0 A ± 0.1 A for 60 seconds ± 1 second Charge: Charge voltage 14.80 V ± 0.03 V (limiting current 25.0 A ± 0.1 A) for 600 seconds ± 1 second (c) During the test, leave it for 56 hours every 480 cycles, then perform continuous discharge at a rated cold cranking current of 390 A for 30 seconds, and record the voltage at the 30th second. Then, perform the charge in (b). Note that these discharges and charges are also added to the number of life cycles (number of cycles). The test is terminated when it is confirmed that the voltage at the 30th second measured in the test of (d)(c) is 7.2 V or less and does not rise again. The total number of cycles at this time (hereinafter sometimes referred to as "cycle number N") is used as an index of the life performance. Note that the rated cold cranking current is a measure representing the engine starting performance, and is the discharge current defined so that the voltage at the 30th second becomes 7.2 V or more when discharging at a temperature of -18°C ± 1°C.

[0103] (2) Tensile strength The tensile strength of the separator is measured by the following procedure. First, a test piece is obtained by cutting the separator into a size of 10 mm × 40 mm. For this test piece, a tensile test is performed using a precision universal testing machine (Shimadzu Corporation, product name: AGS-X) under the conditions of a chuck distance of 20 mm, a tensile speed of 5 mm / min, and a temperature of 25°C, and the stress at the time of fracture is defined as the tensile strength.

[0104] Hereinafter, an example of the lead-acid battery according to the present embodiment will be specifically described with reference to the drawings. The above-described components can be applied to the components of the example of the lead-acid battery described below. Further, the components of the example of the lead-acid battery described below can be changed based on the above description. Further, the matters described below may be applied to the above embodiment. Further, in the embodiment described below, components that are not essential to the lead-acid battery according to the present embodiment may be omitted.

[0105] FIG. 1 shows the appearance of an example of the lead-acid battery according to the embodiment of the present invention. The lead-acid battery 1 includes a battery case 12 that houses a plate group 11 and an electrolytic solution (not shown). Inside the battery case 12, a plurality of cell chambers 14 are partitioned by a partition wall 13. One plate group 11 is housed in each cell chamber 14. The opening of the battery case 12 is closed by a lid 15 having a negative terminal 16 and a positive terminal 17. The lid 15 is provided with a liquid plug 18 for each cell chamber. When replenishing water, the liquid plug 18 is removed and replenishing liquid is supplied. The liquid plug 18 may have a function of discharging the gas generated in the cell chamber 14 to the outside of the battery.

[0106] The electrode plate group 11 is configured by stacking a plurality of negative electrode plates 2 and positive electrode plates 3 via separators 4. Here, a bag-shaped separator 4 for accommodating the negative electrode plates 2 is shown, but the form of the separator is not particularly limited. In the cell chamber 14 located at one end of the battery container 12, a negative electrode grid portion 6 for connecting a plurality of negative electrode plates 2 in parallel is connected to the through-connector 8, and a positive electrode grid portion 5 for connecting a plurality of positive electrode plates 3 in parallel is connected to the positive electrode post 7. The positive electrode post 7 is connected to the positive electrode terminal 17 outside the lid 15. In the cell chamber 14 located at the other end of the battery container 12, a negative electrode post 9 is connected to the negative electrode grid portion 6, and the through-connector 8 is connected to the positive electrode grid portion 5. The negative electrode post 9 is connected to the negative electrode terminal 16 outside the lid 15. Each through-connector 8 passes through a through-hole provided in the partition wall 13 and connects the electrode plate groups 11 in adjacent cell chambers 14 in series.

[0107] The matters described in this specification can be arbitrarily combined.

[0108] [Examples] Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to the following examples.

[0109] (Experimental Example 1) In Experimental Example 1, a plurality of separators and a plurality of lead-acid batteries were produced according to the following procedure.

[0110] (1) Production and evaluation of separators A resin composition containing 100 parts by mass of polyethylene, 160 parts by mass of silica particles, 80 parts by mass of paraffinic oil as a pore-forming agent, and 2 parts by mass of a penetrant was extruded into a sheet shape, subjected to a stretching treatment, and then a part of the pore-forming agent was removed to produce a porous membrane having ribs on one side. At this time, the cooling rate of the extruded sheet and the magnification of the stretching treatment were adjusted so that the crystallinity of the porous membrane required by the above-described procedure became the value shown in Table 1.

[0111] 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 membranes according to the following procedure. First, a mixture of silica and a carbon material was deposited on the separator, and then a pure carbon layer was deposited thereon by a roller coating method or a spray coating method. In this way, the carbon material was placed. The thickness of the carbon material was made the same for each porous membrane. Specifically, it was 10 μm. By the above procedure, a plurality of separators with different degrees of crystallinity of the porous membrane were produced.

[0112] The oil content of the separator obtained by the above-described procedure was 11 to 18% by mass, and the content of silica particles was 60% by mass. The height of the rib obtained by the above-described procedure was 0.6 mm. The thickness (thickness of the base portion) of the separator obtained by the above-described procedure is shown in Table 1.

[0113] The sheet-like separator obtained by the above procedure was folded in half so that ribs were arranged on the outer surface to form a bag. Next, a bag-shaped separator was obtained by crimping both overlapping ends. The inner surface of the bag-shaped separator is the surface on which the carbon material was placed.

[0114] Note that the degree of crystallinity, oil content, content of silica particles, thickness of the separator, and height of the rib in the separator are values obtained for the separator before the production of the lead-acid battery. These values are almost the same as the values measured by the above-described procedure for the separator taken out from the lead-acid battery after production.

[0115] (2) Production of positive electrode plate Lead oxide, a reinforcing material (synthetic resin fiber), water, and sulfuric acid were mixed to prepare a positive electrode paste. The positive electrode paste was filled into the mesh portion of an expanded grid made of a Pb-Ca-Sn alloy containing no antimony, and by aging and drying, an unformed positive electrode plate having a width of 100 mm, a height of 110 mm, and a thickness of 1.6 mm was obtained.

[0116] (3) Production of negative electrode plate A negative electrode paste was prepared by mixing lead oxide, carbon black, barium sulfate, lignin, reinforcing material (synthetic resin fiber), water and sulfuric acid. The negative electrode paste was filled into the mesh of an expanded lattice made of a Pb-Ca-Sn alloy not containing antimony, and aged and dried to obtain an unformed negative electrode plate with a width of 100 mm, a height of 110 mm and a thickness of 1.3 mm. The amounts of carbon black, barium sulfate, lignin and synthetic resin fiber used were adjusted so that the contents of each component in the negative electrode plate taken out of a fully charged lead-acid battery were 0.3 mass%, 2.1 mass%, 0.1 mass% and 0.1 mass%, respectively.

[0117] (4) Making a 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 group consisting of seven unformed negative electrode plates and six unformed positive electrode plates.

[0118] The lugs of the positive plates and the lugs of the negative plates were welded to the positive and negative shelf parts, respectively, using the cast-on-strap (COS) method. The plate group was inserted into a polypropylene battery case, electrolyte was poured in, and chemical formation was performed inside the battery case to assemble a flooded lead-acid battery with a rated voltage of 12V and a rated capacity of 30Ah (5-hour rate capacity (capacity when discharged at a current (A) that is 1 / 5 of the Ah value indicated on the rated capacity)). Note that six plate groups were connected in series inside the battery case.

[0119] The electrolyte used was an aqueous sulfuric acid solution. The specific gravity of the electrolyte after formation at 20°C was 1.285.

[0120] The XRD spectrum of the porous film used in the separator of Battery A1, measured by 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 range of 2θ = 21.5° to 22.5°, and a diffraction peak corresponding to the (200) plane was observed in the range of 2θ = 23° to 24.5°. A halo due to the amorphous region was observed broadly in the wide range of 2θ = 17° to 27°.

[0121] Using the obtained lead-acid battery, the life performance (number of cycles N) was evaluated by the aforementioned procedure. The life performance was evaluated by the 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 90. The evaluation results are shown in Table 1. Batteries A1 to A4 are the batteries of the invention examples, and battery CA1 is the battery of the comparative example.

[0122]

Table 1

[0123] As shown in Table 1, when the crystallinity of the porous membrane is 20% or more, the life performance is significantly improved compared to the case where the crystallinity corresponding to the prior art is 18%. This is considered to be because the oxidation resistance of the separator is improved due to the high crystallinity of the porous membrane.

[0124] (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 by the same method as in Experimental Example 1, except that the manufacturing conditions for changing the thickness of the separator and the crystallinity of the porous membrane were changed. The carbon material was arranged under the same conditions as the separator in Experimental Example 1.

[0125] The fabricated 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 the invention examples, and batteries CB1 to CB4 are the comparative examples. The life performance (number of cycles N) in Table 2 is the relative value when the number of cycles N of battery B1 is 100.

[0126]

Table 2

[0127] As shown in Table 2, by setting the thickness of the separator to 100 μm or more, the life performance could be significantly improved. When the separator is thin (when the porous membrane is thin), during resin molding for forming the porous membrane, the resin flow around the mold deteriorates, resulting in larger variations in thickness and pore size, or partial cracking (the separator tearing) may occur. On the other hand, when the thickness of the separator is 100 μm or more (the thickness of the porous membrane is 90 μm or more), the resin flow improves and a homogeneous porous membrane can be obtained. In addition, by disposing a carbon material on the surface of the porous membrane, as described later, the tensile strength of the separator is significantly improved. Therefore, it is considered that the life characteristics are significantly improved.

[0128] (Experimental Example 3) In Experimental Example 3, a plurality of separators were fabricated by changing the production conditions. Specifically, a plurality of separators were fabricated in the same manner as in Experimental Example 1, except that the production conditions for changing the crystallinity of the porous membrane and the thickness of the separator, and the presence or absence of the arrangement of the carbon material were changed. The fabricated separators were evaluated in the same manner as in Experimental Example 1.

[0129] Furthermore, for the fabricated separators, the tensile strength was measured by the method described above. The evaluation results of the separators are shown in Table 3 and Table 4. Separators S1 to S10 are the separators of the inventive examples, and separators CS1 to CS12 are the separators of the comparative examples. The tensile strength is the relative value when the tensile strength of separator CS1 is set to 100.

[0130]

Table 3

[0131]

Table 4

[0132] The results of Table 3 are shown in FIG. 3, and the results of Table 4 are shown in FIG. 4. As shown in Table 3 and FIG. 3, by disposing a carbon material on the surface and setting the crystallinity of the porous film to 20% or more, the tensile strength of the separator could be significantly increased. As shown in Table 4 and FIG. 4, by disposing 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.

[0133] As shown in FIG. 3, in the separator on which the carbon material was disposed, the effect of increasing the tensile strength by increasing the crystallinity was higher than that of the separator on which the carbon material was not disposed. As shown in FIG. 4, in the separator on which the carbon material was disposed, the effect of increasing the tensile strength by increasing the thickness of the separator was higher than that of the separator on which the carbon material was not disposed. Although the reasons for these are not clear, it is considered that disposing the carbon material on the surface of the porous film exhibits some synergistic effect.

Industrial Applicability

[0134] The present invention can be used for lead-acid batteries and separators used therein. The separator for a lead-acid battery of the present invention is suitable, for example, for IS applications (such as lead-acid batteries for ISS vehicles), starting power sources for various vehicles (automobiles, motorcycles, etc.). The separator for a lead-acid battery can also be preferably used for power sources such as industrial power storage devices (such as forklifts) of electric vehicles. Note that these applications are merely examples. The applications of the separator for a lead-acid battery and the lead-acid battery of the present invention are not limited to these.

Explanation of Reference Numerals

[0135] 1: Lead-acid battery, 2: Negative electrode plate, 3: Positive electrode plate, 4: Separator, 5: Positive electrode grid part, 6: Negative electrode grid part, 7: Positive electrode post, 8: Through-connection body, 9: Negative electrode post, 11: Electrode plate group, 12: Battery case, 13: Partition wall, 14: Cell chamber, 15: Cover, 16: Negative electrode terminal, 17: Positive electrode terminal, 18: Liquid port plug

Claims

1. A separator for a lead-acid battery, comprising: a porous membrane containing a polymer material and a carbon material disposed on the surface of the porous membrane, wherein the porous membrane includes a crystalline region and an amorphous region, In the X-ray diffraction spectrum of the porous membrane, the crystallinity represented by 100×I ｃ / (I ｃ + I ａ ) is 20% or more and 35% or less, I ｃ is the integrated intensity of the diffraction peak with 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, and the separator for a lead-acid battery has a thickness of 100 μm or more and 300 μm or less.

2. The separator for a lead-acid battery according to claim 1, containing oil.

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

4. The polyolefin contains at least an ethylene unit, and the diffraction peak with the maximum peak height corresponds to the (110) plane by the crystalline region. The separator for a lead-acid battery according to claim 3.

5. The separator for a lead-acid battery according to any one of claims 1 to 4, wherein the carbon material is at least one selected from the group consisting of conductive carbon black and conductive carbon fibers.

6. A lead-acid battery, comprising: at least one cell including a plate group and an electrolyte, wherein the 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, and the separator is the separator for a lead-acid battery according to any one of claims 1 to 5.

7. In the lead-acid battery according to claim 6, the carbon material of the separator is disposed on the main surface on the negative electrode plate side of the two main surfaces of the porous membrane.

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