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

Abstract

SOLUTION: This separator for lead storage batteries includes a crystalline region and an amorphous region. In the X-ray diffraction spectrum of the separator, the ratio R indicated by A1 / (A1+A2) is 0.60 or greater. A1 represents the area of a first diffraction peak, the peak height of which among the diffraction peaks equivalent to the crystalline region is maximum, and A2 represents the area of a second diffraction peak, the peak height of which among the diffraction peaks equivalent to the crystalline region is second highest. A sum total Vt of volumes of pores having a power size of 0.005 μm to 10 μm, inclusive, is 0.8 cm3 / g or greater.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 electrolyte. Various performances are required for the separator of a lead-acid battery.

[0003] Patent Document 1 proposes a separator for a lead-acid battery including a polyolefin microporous membrane, wherein the polyolefin microporous membrane includes polyethylene, which is preferably ultra-high molecular weight polyethylene, a particulate filler, and a processing plasticizer, the particulate filler is present in an amount of 40% or more by weight, the polyethylene includes a polymer having a shish-kebab structure including a plurality of extended-chain crystals (shish formation) and a plurality of folded-chain crystals (kebab formation), and an average repeat or period of the kebab formation is from 1 nm to 150 nm, preferably less than 120 nm.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When the pore volume of the separator increases, the resistance decreases, so that the CCA (Cold Cranking Amps) performance can be improved. However, when the pore volume increases, the strength of the separator decreases, so that the separator is damaged during the manufacturing process of the lead-acid battery, and a short circuit is likely to occur at the initial stage of the lead-acid battery, and the initial defect rate of the lead-acid battery may increase.

Means for Solving the Problems

[0006] One aspect of the present invention is a separator for a lead-acid battery, the separator includes a crystalline region and an amorphous region, in the X-ray diffraction spectrum of the separator, the ratio R represented by A1 / (A1 + A2) is 0.60 or more, A1 is the area of the first diffraction peak having the largest peak height among the diffraction peaks corresponding to the crystalline region, A2 is the area of the second diffraction peak having the second highest peak height among the diffraction peaks corresponding to the crystalline region, the total volume Vt of pores having a pore diameter of 0.005 μm or more and 10 μm or less (hereinafter, may be referred to as first pores) is 0.8 cm 3 / g or more, and relates to a separator for a lead-acid battery.

Advantages of the Invention

[0007] To provide a separator that can ensure high CCA performance and reduce the initial defect rate in a lead-acid battery.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0009] In a separator for a lead-acid battery, the total volume Vt of pores having a pore diameter of 0.005 μm or more and 10 μm or less (first pores) is 0.8 cm 3When it is above / g, high diffusibility of the electrolytic solution can be obtained, and the resistance of the separator can be kept low. Since the discharge reaction proceeds smoothly, the CCA performance can be improved. However, when the total volume Vt of the first pores is 0.8 cm 3 When it is above / g, the physical strength of the separator decreases, so that short circuits are likely to occur due to breakage. In the manufacturing process of the electrode plate, the corners may be deformed due to interference with the manufacturing apparatus. When a lead-acid battery is manufactured using the deformed electrode plate, at the initial stage, the corners of the electrode plate are likely to pierce through the separator and cause a short circuit. Therefore, when the total volume Vt of the first pores is 0.8 cm 3 When it is above / g, short circuits of the lead-acid battery occur at the initial stage, and the occurrence rate of short circuits (initial defect occurrence rate) tends to increase. If the thickness of the separator is increased, the strength increases and the initial defect occurrence rate decreases. However, since the resistance increases, the CCA performance decreases. Therefore, it is difficult to keep the initial defect occurrence rate low while ensuring high CCA performance. Hereinafter, the total volume Vt of the first pores may be simply referred to as the first pore volume Vt.

[0010] In view of the above, the separator for a lead-acid battery according to one aspect of the present invention includes a crystalline region and an amorphous region. In the X-ray diffraction (XRD) spectrum of the separator, the ratio R represented by A1 / (A1 + A2) is 0.60 or more. Here, A1 is the area of the diffraction peak (the 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 (the second diffraction peak) having the second highest peak height among the diffraction peaks corresponding to the crystalline region. In the separator, the total volume Vt of pores (first pores) having a pore diameter of 0.005 μm or more and 10 μm or less is 0.8 cm 3 When it is above / g.

[0011] The ratio R indicates the degree of crystallinity of the separator. In conventional separators, for example, the ratio R tends to be relatively low, approximately 0.58 or less. In contrast, for the separator of the above aspect, the ratio R is 0.60 or more, and the crystallinity of the separator is higher than that of the conventional ones. By increasing the crystallinity of the separator, the strength of the separator itself can be improved, so that the initial defect rate can be reduced compared to the conventional ones. Moreover, unlike the case of increasing the thickness of the separator, there is almost no trade-off such as an increase in resistance. Therefore, by sufficiently exerting the effect of improving the diffusibility of the electrolyte and the effect of reducing the resistance by increasing the first pore volume Vt to 0.8 cm 3 / g or more, high CCA performance can be maintained.

[0012] The separator for a lead-acid battery has a certain thickness, which is different from separators for lithium-ion secondary batteries and the like. In addition, the greater the thickness of the separator, the more difficult it is to increase the crystallinity. Moreover, as the crystallinity increases, the separator tends to become hard and brittle. From such a perspective, in conventional separators for lead-acid batteries, the crystallinity has not been controlled. Against such conventional common sense, in the separator for a lead-acid battery of one aspect of the present invention, when the first pore volume Vt is 0.8 cm 3 / g or more, by setting the ratio R to 0.60 or more, it is possible to ensure high strength of the separator while suppressing an increase in the resistance of the separator. Therefore, high CCA can be ensured and the initial defect rate can be suppressed.

[0013] The total volume Vt of the first pores (the first pore volume Vt) in the separator is the sum of the volumes of the first pores (pores having a pore diameter of 0.005 μm or more and 10 μm or less) in the separator determined by the mercury intrusion method.

[0014] The ratio R is preferably 0.70 or more. In this case, since the strength of the separator is further increased, the initial defect rate can be further reduced.

[0015] The first pore volume Vt is preferably 1.0 cm 3 / g or more. In this case, the CCA performance can be further enhanced.

[0016] The separator preferably contains a polyolefin, and more preferably contains a polyolefin containing at least an ethylene unit. Such a separator tends to have a relatively low strength, but the adjustment of the ratio R is relatively easy, and the strength of the separator can be increased by adjusting the ratio R. Therefore, the initial defect occurrence rate can be further reduced. When the separator 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.

[0017] The thickness of the separator is preferably 100 μm or more and 300 μm or less. When the thickness is in such a range, a higher strength of the separator can be ensured, so the effect of reducing the initial defect occurrence rate is enhanced. Also, since the resistance of the separator can be kept relatively low, excellent CCA performance is easily obtained.

[0018] The separator preferably contains oil. In this case, the effect of suppressing the oxidative degradation of the separator is enhanced, which is advantageous in terms of extending the service life.

[0019] The present invention also includes a lead-acid battery including the above-described separator for a lead-acid battery. The lead-acid battery includes at least one cell including a plate group and an electrolyte, and the plate group includes a positive electrode plate, a negative electrode plate, and the above-described separator interposed between the positive electrode plate and the negative electrode plate. By using the above-described separator, a high CCA performance can be ensured while reducing the initial defect occurrence rate of the lead-acid battery. By increasing the strength of the separator, it is possible to suppress a penetration short circuit or a short circuit caused by the bending of the electrode plate. Therefore, the life performance can also be enhanced.

[0020] The lead-acid battery may be a valve-regulated battery (VRLA battery), but a flooded battery (vented battery) is preferred.

[0021] In this specification, the vertical direction of a lead-acid battery or components of a lead-acid battery (such as electrode plates, battery cases, separators, etc.) means the vertical direction in the vertical direction of the lead-acid battery when the lead-acid battery is in use. Each of the positive and negative electrode plates is provided with an ear portion for connecting to an external terminal. In a liquid-type battery, the ear portion is provided so as to protrude upward from the upper part of the electrode plate.

[0022] Hereinafter, the separator and the lead-acid battery according to embodiments of the present invention will be described more specifically with reference to the drawings. However, the present invention is not limited to the following embodiments.

[0023] (Separator) The separator includes a crystalline region in which the molecules of the constituent material of the separator are relatively regularly arranged (that is, the degree of arrangement is high) and an amorphous region with a low degree of arrangement. Therefore, in the XRD spectrum of the separator, 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 separator, when the ratio R represented by A1 / (A1 + A2) is 0.60 or more, high strength of the separator can be obtained. Here, A1 is the area of the diffraction peak with the maximum peak height among the diffraction peaks corresponding to the crystalline region (the first diffraction peak), and A2 is the area of the diffraction peak with the second highest peak height among the diffraction peaks corresponding to the crystalline region (the second diffraction peak).

[0024] For example, in the XRD spectrum of a separator containing a polyolefin containing ethylene units, a diffraction peak corresponding to the (110) plane of the crystalline region is observed in the range where 2θ is 20° or more and 22.5° or less, and a 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. The diffraction peak corresponding to the (200) plane has the second highest peak height and corresponds to the second diffraction peak.

[0025] The ratio R is 0.60 or more, and from the viewpoint of ensuring higher strength of the separator, it may be 0.70 or more. The ratio R may be 0.90 or less, may be 0.85 or less, or may be 0.80 or less. When the ratio R is within such a range, in addition to being able to ensure the flexibility of the separator, the manufacturing is easy.

[0026] The ratio R may be 0.60 or more (or 0.70 or more) and 0.90 or less, 0.60 or more (or 0.70 or more) and 0.85 or less, or 0.60 or more (or 0.70 or more) and 0.80 or less.

[0027] The area of the diffraction peak is obtained by fitting the diffraction peak due to the crystalline region in the XRD spectrum of the separator. Using the obtained area A1 of the first diffraction peak and area A2 of the second diffraction peak, the ratio R is obtained from the above formula.

[0028] The first pore volume Vt in the separator is 0.8 cm 3 / g or more. When the first pore volume Vt is within such a range, high diffusibility of the electrolyte can be obtained, and the resistance of the separator can be kept low. Therefore, excellent CCA performance can be ensured. From the viewpoint of ensuring higher CCA performance, the first pore volume Vt is preferably 0.9 cm 3 / g or more, more preferably 1.0 cm 3 / g or more or 1.05 cm 3 / g or more. The first pore volume Vt is, for example, 2.2 cm 3 / g or less. From the viewpoint that the effect of reducing the initial defect occurrence rate by increasing the ratio R is more likely to be exerted, the first pore volume Vt is preferably 2.0 cm 3 / g or less, more preferably 1.9 cm 3 / g or less.

[0029] The first pore volume Vt is 0.8 cm 3 / g or more and 2.2 cm 3 / g or less (or 2.0 cm3 less than 0.9 cm per g 3 2.2 cm or more per g 3 less than 2.0 cm per g (or 3 less than 1.0 cm per g 3 2.2 cm or more per g 3 less than 2.0 cm per g (or 3 less than 1.05 cm per g 3 2.2 cm or more per g 3 less than 2.0 cm per g (or 3 less than 0.8 cm per g 3 0.9 cm or more per g (or 3 1.9 cm or more per g 3 less than 1.0 cm per g, or 3 1.05 cm or more per g (or 3 1.9 cm or more per g 3 It may be less than per g.

[0030] The separator contains a polymer material (hereinafter also referred to as the base polymer). Since the separator contains a crystalline region, the base polymer usually contains a crystalline polymer. The separator 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).

[0031] 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 separator 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 this large, the strength of the separator tends to be low. However, even in such a case, in order to make the ratio R within the above range, high strength can be ensured and the initial defect occurrence rate can be suppressed low.

[0032] Polyolefins include, for example, homopolymers of olefins, copolymers containing different olefin units, and copolymers containing olefin units and copolymerizable monomer units. The copolymer containing olefin units and copolymerizable monomer units may contain one or more olefin units. Further, the copolymer containing olefin units and copolymerizable monomer units may contain one or more copolymerizable monomer units. The copolymerizable monomer unit is a monomer unit derived from a polymerizable monomer other than olefins and copolymerizable with olefins.

[0033] Examples of polyolefins include polymers containing at least C 2-3 polymers containing 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). Polyolefins containing ethylene units (such as polyethylene and ethylene-propylene copolymers) may be used in combination with other polyolefins.

[0034] The separator preferably contains oil. When the separator contains oil, the effect of suppressing the oxidative degradation of the separator can be further enhanced, which is advantageous in terms of extending the service life. 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. Mineral oils, synthetic oils, etc. are preferred as oils. 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.

[0035] The oil content in the separator may be 11% by mass or more, or may be 12% by mass or more. The oil content may be 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 enhanced, which is advantageous in terms of extending the service life. Also, the resistance of the separator can be kept relatively low.

[0036] The separator may be in a sheet form. 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 with the bag-shaped separator.

[0037] The separator may have ribs or may not have ribs. The separator having ribs includes, for example, a base portion and ribs standing from the surface of the base portion. The ribs may be provided only on one surface of the separator or each base portion, or may be provided on both surfaces respectively. Note that the base portion of the separator is a portion excluding protrusions such as ribs among the constituent parts of the separator, and refers to the sheet-shaped portion defining the outer shape of the separator.

[0038] The thickness of the separator is, for example, 90 μm or more. From the viewpoint of further reducing the initial defect rate, 100 μm or more or 150 μm or more is preferable. 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 a base portion and ribs standing from 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 (mat, pasting paper, etc.) is attached to the separator, the thickness of the attachment member is not included in the thickness of the separator.

[0039] The thickness of the separator may be 90 μm or more and 300 μm or less (or 250 μm or less), 90 μm or more and 200 μm or less, 100 μm or more (or 150 μm or more) and 300 μm or less, 100 μm or more (or 150 μm or more) and 250 μm or less, or 100 μm or more (or 150 μm or more) and 200 μm or less.

[0040] 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).

[0041] 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.

[0042] The separator 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 separator (or the resin composition used for manufacturing the separator) may contain inorganic particles. The sheet-shaped separator is dried as necessary after removing the pore former. For example, the ratio R is adjusted by adjusting at least one selected from the group consisting of the cooling rate of the sheet during extrusion molding, the stretching ratio during 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 ratio R 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.

[0043] In the separator having ribs, the ribs may be formed on the sheet when the resin composition is extrusion-molded. 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.

[0044] The pore structure and the first pore volume Vt in the separator can be adjusted by adjusting the affinity between the base polymer and the pore-forming agent and / or the penetration agent, adjusting the dispersibility of the pore-forming agent, selecting the type and / or particle diameter of the inorganic particles, selecting the type of the penetration agent, adjusting the amount of the inorganic particles, the amount of the pore-forming agent, and / or the amount of the penetration agent, and / or adjusting the amount of functional groups and / or atoms present on the surface of the inorganic particles.

[0045] 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. 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.

[0046] As the liquid pore-forming agent, the above-mentioned oil is preferable. Examples of the solid pore-forming agent include polymer powder.

[0047] The amount of the pore-forming agent in the separator may vary depending on the type. The amount of the pore-forming agent in the separator is, for example, 30 parts by 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.

[0048] For example, a separator containing oil is formed by extracting and removing part of the oil from a sheet formed using oil as a pore former with a solvent. The solvent is selected according to, for example, the type of 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 separator is adjusted.

[0049] As the surfactant as a penetrant, for example, either an ionic surfactant or a nonionic surfactant may be used. The surfactant may be used alone or in combination of two or more.

[0050] The content of the penetrant in the separator is, for example, 0.01% by mass or more, and may be 0.1% by mass or more. The content of the penetrant in the separator may be 10% by mass or less.

[0051] 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.

[0052] The content of the inorganic particles in the separator may be, for example, 40% by mass or more. The content of the inorganic particles is, for example, 80% by mass or less, and may be 70% by mass or less.

[0053] (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-acid battery at the initial stage of use is used. The separator taken out from the lead-acid battery is washed and dried prior to analysis or measurement.

[0054] The cleaning and drying of the separator removed from the lead-acid battery are performed according to the following procedure. The separator removed 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 dry it.

[0055] 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 charged until it shows a constant value with three significant figures continuously for three times. The state of being fully charged is the fully charged state. The numerical value described as the rated capacity is a numerical value with the unit of Ah. The unit of the current set based on the numerical value described as the rated capacity is A.

[0056] 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).

[0057] In this specification, the battery in the initial stage of use is a battery that has not elapsed much time and has hardly deteriorated after the start of use.

[0058] (XRD spectrum) The XRD spectrum of the separator is measured by irradiating X-rays from a direction perpendicular to the surface of the separator. The sample for measurement is prepared by processing the portion of the separator facing the electrode material into a strip shape. In the case of a separator having ribs, 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 conditions. (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).

[0059] (First pore volume Vt) Process the part of the separator facing the electrode material into a strip shape of 20 mm × 5 mm to prepare a sample (hereinafter referred to as sample A). For a separator with ribs, the base part is processed into a strip shape so as not to include the ribs to prepare sample A. For sample A, the pore distribution is determined under the following conditions using a mercury porosimeter, and Vt is obtained by summing the volumes of the first pores. Mercury porosimeter: AutoPore IV9510, manufactured by Shimadzu Corporation Measurement pressure range: 4 psia (≈27.6 kPa) or more and 60,000 psia (≈414 MPa) or less Pore distribution: 0.01 μm or more and 50 μm or less

[0060] (Separator thickness and rib height) The thickness of the separator is determined by measuring the thickness at five arbitrarily selected locations in the cross-sectional photograph of the separator and averaging them.

[0061] The height of the rib is determined by averaging the height from one surface of the base part of the rib measured at ten arbitrarily selected locations of the rib in the cross-sectional photograph of the separator.

[0062] (Oil content in the separator) Process the part of the separator facing the electrode material into a strip shape to prepare a sample (hereinafter referred to as sample B). For a separator with ribs, the base part is processed into a strip shape so as not to include the ribs to prepare sample B.

[0063] Collect about 0.5 g of Sample B, accurately weigh it, and determine the mass (m0) of the initial sample. Put the weighed Sample B into a glass beaker of appropriate size, and add 50 mL of n-hexane. Then, apply ultrasonic waves to the sample in the beaker for about 30 minutes to elute the oil content contained in Sample B into n-hexane. Next, take out the sample from n-hexane, dry it in the air at room temperature (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 according to the following formula. Determine the oil content for 10 samples of Sample B and calculate the average value. Take the obtained average value as the oil content in the separator. Oil content (mass %) = (m0 - m1) / m0 × 100

[0064] (Content of inorganic particles in the separator) Collect a part of Sample B prepared in the same manner as above, accurately weigh it, then put it into a platinum crucible, and heat it with a Bunsen burner until no white smoke comes out. Next, heat the obtained sample in an electric furnace (in an oxygen stream, 550°C ± 10°C) for about 1 hour to incinerate it, and weigh the incinerated product. Calculate the ratio (percentage) of the mass of the incinerated product to the mass of Sample B, and take it as the content of the above inorganic particles (mass %). Determine the content of inorganic particles for 10 samples of Sample B and calculate the average value. Take the obtained average value as the content of inorganic particles in the separator.

[0065] (Content of penetrant in the separator) A part of Sample B prepared in the same manner as described above is collected, accurately weighed, and then dried 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. The dried product is placed in a platinum cell, set in a thermogravimetric analyzer, and heated from room temperature to 800°C ± 1°C at a heating rate of 10 K / min. The mass reduction amount when heating 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. The content rates of the penetrant are determined for 10 samples of Sample B, and the average value is calculated. The obtained average value is used as the content rate of the penetrant in the separator.

[0066] (Positive electrode plate) As the positive electrode plate, a pasty positive electrode plate is used. The pasty positive electrode plate includes a positive electrode current collector and a positive electrode electrode material. The positive electrode electrode material is held by the positive electrode current collector. The positive electrode electrode material is the part of the positive electrode plate excluding the positive electrode current collector. Note that members such as a mat and pasting paper may be attached to the electrode plate. Since such a member (also referred to as an attached member) is used integrally with the electrode plate, it is included in the electrode plate. When the positive electrode plate includes an attached member, the positive electrode electrode material is the part of the positive electrode plate excluding the positive electrode current collector and the attached member.

[0067] The positive electrode current collector included in the positive electrode plate may be formed by casting lead (Pb) or a lead alloy, or may be formed by processing a lead or lead alloy sheet. Examples of the processing method include expand processing or punching processing. It is preferable to use a lattice-shaped current collector as the positive electrode current collector because it is easy to carry the positive electrode electrode material.

[0068] As the lead alloy used for the positive electrode current collector, Pb-Ca-based alloys and Pb-Ca-Sn-based alloys are preferable 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 one layer or multiple layers.

[0069] The positive electrode material contained in the positive electrode plate includes a positive electrode active material (lead dioxide or lead sulfate) that exhibits capacitance through a redox reaction. The positive electrode material may contain other additives (such as reinforcing materials) as required.

[0070] 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.

[0071] 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.

[0072] The unformed paste-type positive electrode plate can be 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 other additives (such as reinforcing materials) as required and kneading them.

[0073] The positive electrode plate can be obtained by forming the unformed positive electrode plate. The forming can be performed by charging the electrode plate group including the unformed positive electrode plate in a state where it is immersed in an electrolytic solution containing sulfuric acid in the battery case of a lead storage battery. However, the forming may be performed before assembling the lead storage battery or the electrode plate group.

[0074] (Negative electrode plate) The negative electrode plate of the lead-acid battery is composed of a negative current collector and a negative electrode material. The negative electrode material is the part of the negative electrode plate excluding the negative current collector. Note that in some cases, the above-mentioned sticking member may be stuck to the negative electrode plate. In this case, the sticking member is included in the negative electrode plate. When the negative electrode plate includes the sticking member, the negative electrode material is the part of the negative electrode plate excluding the negative current collector and the sticking member.

[0075] The negative current collector can be formed in the same manner as the positive current collector. At least one of the positive current collector and the negative current collector may be a current collector formed by expansion processing.

[0076] In particular, for a plate using a current collector formed by expansion processing, deformation is likely to occur in the manufacturing process of the plate, and an initial short circuit is likely to occur. Therefore, the initial defect occurrence rate tends to increase. According to the above aspect, since the strength is improved by increasing the crystallinity of the separator, even when at least one of the positive electrode plate and the negative electrode plate includes an expanded lattice, the initial defect occurrence rate can be reduced.

[0077] The lead alloy used for the negative current collector may be any of a Pb-Sb-based alloy, a Pb-Ca-based alloy, and a Pb-Ca-Sn-based alloy. These lead or lead alloys may further contain at least one selected from the group consisting of Ba, Ag, Al, Bi, As, Se, Cu, etc. as an additive element. The negative current collector may have lead alloy layers with different compositions, and the alloy layer may be one layer or multiple layers.

[0078] The negative electrode material included in the negative electrode plate contains a negative active material (lead or lead sulfate) that exhibits capacitance through an oxidation-reduction reaction, and may also 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 required.

[0079] Examples of the organic anti-shrinking agent include lignin, lignin sulfonic acid, synthetic organic anti-shrinking agents (such as formaldehyde condensates of phenolic compounds), etc. The negative electrode material may contain one kind of the organic anti-shrinking agent or may contain two or more kinds.

[0080] The content rate of the organic anti-shrinking agent in the negative electrode material is, for example, 0.01% by mass or more. The content rate of the organic anti-shrinking agent is, for example, 1% by mass or less.

[0081] Examples of the carbonaceous material include carbon black, graphite (artificial graphite, natural graphite, etc.), hard carbon, soft carbon, etc. The negative electrode material may contain one kind of the carbonaceous material or may contain two or more kinds.

[0082] 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.

[0083] 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.

[0084] 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.).

[0085] 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.

[0086] The negative electrode active material in the charged state is spongy lead, but the unformed negative electrode plate is usually produced using lead powder.

[0087] 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 prepared by adding water and sulfuric acid to lead powder, an organic shrinkage inhibitor, 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 a high humidity.

[0088] Formation can be carried out by charging a group of electrode plates including an unformed negative electrode plate in a state where the group of electrode plates is immersed in an electrolytic solution containing sulfuric acid in the battery case of a lead storage battery. However, formation may be carried out before the assembly of the lead storage battery or the group of electrode plates. Spongy lead is generated by formation.

[0089] (Electrolytic solution) The electrolytic solution is an aqueous solution containing sulfuric acid. The electrolytic solution may be gelled as required.

[0090] 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.

[0091] The specific gravity of the electrolytic solution at 20°C is, for example, 1.10 or more. The specific gravity of the electrolytic solution at 20°C may be 1.35 or less. These specific gravities are values for the electrolytic solution of a fully charged lead storage battery.

[0092] Hereinafter, the evaluation methods for each characteristic will be described.

[0093] (1) CCA performance In accordance with JIS D 5301:2006, the starting performance of the lead storage battery is evaluated by the current value at which the terminal voltage becomes 7.2 V or more 30 seconds after the start of discharge according to the following procedure. The larger the current value, the higher the starting performance, which means that the resistance of the separator is low. (a) After the completion of full charge, place the storage battery in a cooling chamber at -18°C ± 1°C for at least 16 hours. (b) After confirming that the electrolyte temperature of any cell in the center is -18°C ± 1°C, discharge for 30 seconds with CCA390A. (c) Record the terminal voltage at the 30th second after the start of discharge.

[0094] (2) Initial short - circuit occurrence rate (initial defect occurrence rate) (a) Stack seven unformed negative plates and six unformed positive plates alternately, which are accommodated in a bag - shaped separator, to assemble a plate group with unformed negative plates at both ends. At this time, visually check whether there are holes in the separator due to the bending of the current collector. (b) Place six plate groups in which no holes in the separator were confirmed in (a) into each cell chamber of the battery tank respectively, inject electrolyte, and perform formation treatment to fabricate lead - acid batteries. (c) Discharge the formed lead - acid battery for 2.5 seconds with a current (A) that is 8.3 times the numerical value described as the rated capacity in units of Ah. If the voltage after discharge is 9.5 V (1.58 V / cell) or less, it is judged as a discharge defect. (d) By summing the number of bag - shaped separators with holes confirmed in (a) and the number of bag - shaped separators with holes confirmed in the plate group judged as having a discharge defect in (c), obtain the number n1 of bag - shaped separators in which defects occurred. (e) Divide the number n1 of bag - shaped separators in which defects occurred by the total number N of bag - shaped separators fabricated to obtain the ratio of bag - shaped separators in which defects occurred, and use it as the initial defect occurrence rate (initial battery short - circuit ratio) (ppm). The total number N of bag - shaped separators fabricated is the sum of the value obtained by multiplying the number of lead - acid batteries fabricated in (b) (= mass - production quantity (for example, 100,000)) by the number of all bag - shaped separators included in one lead - acid battery (= 7×6 = 42) and the total number of bag - shaped separators included in the plate group equipped with the separator with holes confirmed in (a).

[0095] 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 houses a plate group 11 and an electrolyte (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 port plug 18 for each cell chamber. When replenishing water, the liquid port plug 18 is removed and replenishing liquid is supplied. The liquid port plug 18 may have a function of discharging gas generated in the cell chamber 14 to the outside of the battery.

[0096] The plate group 11 is formed by stacking a plurality of negative plates 2 and positive plates 3 via separators 4. Here, a bag-shaped separator 4 for housing the negative 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 case 12, a negative plate rack portion 6 for connecting a plurality of negative plates 2 in parallel is connected to a through-connector 8, and a positive plate rack portion 5 for connecting a plurality of positive plates 3 in parallel is connected to a positive electrode post 7. The positive electrode post 7 is connected to the positive terminal 17 outside the lid 15. In the cell chamber 14 located at the other end of the battery case 12, a negative electrode post 9 is connected to the negative plate rack portion 6, and a through-connector 8 is connected to the positive plate rack portion 5. The negative electrode post 9 is connected to the negative terminal 16 outside the lid 15. Each through-connector 8 passes through a through-hole provided in the partition wall 13 and connects the plate groups 11 of adjacent cell chambers 14 in series.

[0097] The matters described in this specification can be arbitrarily combined.

[0098] [Examples] Hereinafter, the present invention will be specifically described based on examples and comparative examples, but the present invention is not limited to the following examples.

[0099] 《Lead-acid batteries E1 to E15 and C1 to C9》 Each lead-acid battery was manufactured according to the following procedure. (1) Manufacture of separator A resin composition containing 100 parts by mass of polyethylene, approximately 160 parts by mass of silica particles, approximately 80 parts by mass of paraffinic oil as a pore-forming agent, and 2 parts by mass of a penetrant was extrusion-molded into a sheet shape, subjected to a stretching treatment, and then a part of the pore-forming agent was removed to produce a microporous 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 separator ratio R obtained by the above-described procedure became the values shown in Table 1. Further, the amount of silica particles and the amount of the pore-forming agent with respect to polyethylene were adjusted so that the first pore volume Vt obtained by the above-described procedure became the values shown in Table 1.

[0100] The oil content obtained by the above-described procedure was approximately 15% by mass, and the content of silica particles was 60% by mass. The height of the ribs obtained by the above-described procedure was 0.6 mm. The thickness of the separator (the thickness of the base portion) obtained by the above-described procedure was 0.2 mm.

[0101] Next, the sheet-shaped microporous membrane was folded in half so that ribs were arranged on the outer surface to form a bag, and both ends that were overlapped were crimped to obtain a bag-shaped separator.

[0102] Note that the separator ratio R, the first pore volume Vt, the oil content, the content of silica particles, the thickness of the base portion, and the height of the ribs are values obtained for the separator before the production of the lead-acid battery, and 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.

[0103] (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 performing 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.

[0104] (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.

[0105] (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 group consisting of seven unformed negative electrode plates and six unformed positive electrode plates.

[0106] 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.

[0107] The electrolyte used was an aqueous sulfuric acid solution. The specific gravity of the electrolyte after formation at 20°C was 1.285.

[0108] (5) Evaluation The XRD spectrum of the separator of Example 1 measured by the above-mentioned procedure 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°.

[0109] Using the obtained lead-acid battery, the CCA performance and the initial defect occurrence rate were evaluated by the above-described procedure. The CCA performance was evaluated by the ratio (%) of the terminal voltage at 30 seconds of each lead-acid battery when the terminal voltage of the lead-acid battery C1 at 30 seconds was set to 100.

[0110] The evaluation results are shown in Table 1 and FIG. 3. E1 to E15 in Table 1 are examples. C1 to C9 are comparative examples.

[0111]

Table 1

[0112] As shown in Table 1 and FIG. 3, when the first pore volume Vt is 0.8 cm 3 / g or more, high CCA performance can be ensured regardless of the ratio R. On the other hand, when the ratio R is the conventional 0.55, when the first pore volume Vt is 0.8 cm 3 / g or more, the initial defect occurrence rate tends to decrease compared to the case where it is less than 0.8 cm 3 / g (comparison between C1 and C2 to C6). In contrast, when the ratio R is 0.60 or more, even when the first pore volume Vt is 0.8 cm 3 / g or more, the initial defect occurrence rate can be greatly reduced. This is considered to be due to the improvement of the strength of the separator by the increase in the crystallinity of the separator.

Industrial Applicability

[0113] The separator for a lead-acid battery according to the above aspect of the present invention is suitable for, for example, IS applications (such as lead-acid batteries for ISS vehicles), starting power sources for various vehicles (such as automobiles and motorcycles), etc. Further, the separator for a lead-acid battery can also be suitably 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 according to the above aspect of the present invention are not limited to these.

Explanation of Signs

[0114] 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, wherein the separator contains a polyolefin and includes a crystalline region and an amorphous region, In the X-ray diffraction spectrum of the separator, A １ / (A １ + A ２ ) is 0.60 or more, A １ is the area of the first diffraction peak with the maximum peak height among the diffraction peaks corresponding to the crystalline region, A ２ is the area of the second diffraction peak with the second highest peak height among the diffraction peaks corresponding to the crystalline region, the first diffraction peak corresponds to the (110) plane of the crystalline region, the second diffraction peak corresponds to the (200) plane of the crystalline region, The total volume Vt of pores having a pore diameter of 0.005 μm or more and 10 μm or less is 0.8 cm ３ / g or more, a separator for a lead storage battery.

2. The separator for a lead-acid battery according to Claim 1, wherein the ratio R is 0.70 or more.

3. The total volume Vt is 1.0 cm ３ / g or more, and the separator for a lead storage battery according to claim 1 or 2.

4. The separator for a lead-acid battery according to Claim 1, wherein the polyolefin contains at least an ethylene unit.

5. The separator for a lead-acid battery according to any one of Claims 1 to 4, having a thickness of 100 μm or more and 300 μm or less.

6. The separator for a lead-acid battery according to any one of Claims 1 to 5, containing oil.

7. A lead-acid battery, wherein the lead-acid battery includes at least one cell containing 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, and the separator is the separator for a lead-acid battery according to any one of Claims 1 to 6.

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