JP2022186312A - Separator for lead storage battery and lead storage battery including the same - Google Patents

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

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

Lead-acid batteries are used in a variety of applications, including in-vehicle use and industrial use. A lead-acid battery includes a positive plate and a negative plate, a separator interposed therebetween, and an electrolyte. Various performances are required for separators of lead-acid batteries.

US Pat. No. 5,300,000 is a separator for lead-acid batteries comprising a polyolefin microporous membrane, said polyolefin microporous membrane comprising polyethylene, preferably ultra high molecular weight polyethylene, a particulate filler, and a treated plasticizer. and wherein the particulate filler is present in an amount of 40% or more by weight, and the polyethylene comprises a shish kebab forming comprising a plurality of extended chain crystals (shish forming) and a plurality of folded chain crystals (kebab forming). wherein the average repetition or period of said kebab formation is between 1 nm and 150 nm, preferably less than 120 nm.

Japanese Patent Publication No. 2019-514173

As the pore volume of the separator increases, the resistance decreases, so CCA (cold cranking current) performance can be enhanced. However, when the pore volume increases, the strength of the separator decreases, so the separator is damaged during the manufacturing process of the lead-acid battery. may increase.

One aspect of the present invention is a lead-acid battery separator,
the separator includes a crystalline region and an amorphous region;
In the X-ray diffraction spectrum of the separator, the ratio R represented by A ₁ /(A ₁ +A ₂ ) is 0.60 or more,
A ₁ is the area of the first diffraction peak having the maximum peak height among the diffraction peaks corresponding to the crystalline region,
_A2 is the area of the second diffraction peak with the second highest peak height among the diffraction peaks corresponding to the crystalline region,
It relates to a lead-acid battery separator, wherein the total volume Vt of pores having a pore diameter of 0.005 μm or more and 10 μm or less (hereinafter sometimes referred to as first pores) is 0.8 cm ³ /g or more.

Provided is a separator capable of ensuring high CCA performance and reducing the rate of initial failures in a lead-acid battery.

BRIEF DESCRIPTION OF THE DRAWINGS It is a partially cutaway perspective view which shows the external appearance and internal structure of the lead storage battery which concerns on one Embodiment of this invention. 4 is an X-ray diffraction spectrum of the lead-acid battery separator of Example 1. FIG. 5 is a graph showing the relationship between the total Vt of the first pore volume of the separator and the initial failure rate and CCA performance in lead-acid batteries of Examples and Comparative Examples.

In the lead-acid battery separator, when the total volume Vt of the pores (first pores) having a pore diameter of 0.005 μm or more and 10 μm or less is 0.8 cm ³ /g or more, high diffusibility of the electrolytic solution is obtained. In addition, 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 Vt of the volume of the first pores is 0.8 cm ³ /g or more, the physical strength of the separator is reduced, so that short circuits are likely to occur due to breakage. In the manufacturing process of the electrode plate, the corner may be deformed due to interference with the manufacturing equipment. When a lead-acid battery is manufactured using a deformed electrode plate, the corners of the electrode plate easily break through the separator at the initial stage, resulting in a short circuit. Therefore, when the total Vt of the volume of the first pores is 0.8 cm ³ /g or more, a short circuit occurs in the lead-acid battery in the initial stage, and the short circuit occurrence rate (initial failure rate) increases. Tend. Increasing the thickness of the separator increases the strength and reduces the initial failure rate. However, due to the increased resistance, the CCA performance is degraded. Therefore, it is difficult to keep the initial failure 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.

In view of the above, a lead-acid battery separator 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 A ₁ /(A ₁ +A ₂ ) is 0.60 or more. Here, A1 is the area of the diffraction peak ( _first diffraction peak) having the maximum peak height among the diffraction peaks corresponding to the crystalline region. _A2 is the area of the diffraction peak having the second highest peak height (second diffraction peak) 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 /g or more.

The ratio R indicates the degree of crystallinity of the separator. Conventional separators, for example, tend to have a relatively low ratio R of approximately 0.58 or less. On the other hand, the ratio R of the side separator is 0.60 or more, and the crystallinity of the separator is higher than that of the conventional separator. By increasing the crystallinity of the separator, the strength of the separator itself can be improved, so that the initial failure rate can be reduced compared to the conventional case. 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 increasing the first pore volume Vt to 0.8 cm ³ /g or more, the effect of improving the diffusibility of the electrolytic solution and the effect of reducing the resistance are sufficiently exhibited, thereby maintaining high CCA performance. can be done.

A separator for a lead-acid battery has a relatively large thickness, unlike a separator for a lithium-ion secondary battery. In addition, the thicker the separator, the more difficult it is to increase the crystallinity, and the higher the crystallinity, the harder and more brittle the separator tends to be. From this point of view, the crystallinity has not been controlled in conventional separators for lead-acid batteries. In contrast to such conventional common sense, in the lead-acid battery separator of one aspect of the present invention, when the first pore volume Vt is 0.8 cm ³ /g or more, the ratio R is set to 0.60 or more. , high strength of the separator can be ensured while suppressing an increase in the resistance of the separator. Therefore, a high CCA can be ensured, and the initial failure rate can be suppressed.

The total Vt of the volume of the first pores in the separator (first pore volume Vt) is the first pores in the separator (pores having a pore diameter of 0.005 μm or more and 10 μm or less) obtained by the mercury porosimetry. is the sum of the volumes of

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

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

The separator preferably contains a polyolefin, more preferably a polyolefin containing at least ethylene units. Such a separator tends to have relatively low strength, but the ratio R can be adjusted relatively easily, and the strength of the separator can be increased by adjusting the ratio R. Therefore, the initial failure rate can be further reduced. When the separator comprises a polyolefin containing at least ethylene units, the first diffraction peak corresponds to the (110) plane due to the crystalline regions and the second diffraction peak corresponds to the (200) plane due to the crystalline regions.

The thickness of the separator is preferably 100 μm or more and 300 μm or less. When the thickness is within such a range, higher strength of the separator can be ensured, so the effect of reducing the rate of initial failures is enhanced. In addition, since the resistance of the separator can be kept relatively low, excellent CCA performance can be easily obtained.

The separator preferably contains oil. In this case, the effect of suppressing oxidative deterioration of the separator is enhanced, which is advantageous in terms of prolonging the life of the separator.

The present invention also includes a lead-acid battery containing the lead-acid battery separator described above. A lead-acid battery includes at least one cell that includes a plate assembly and an electrolyte, and the plate assembly includes a positive plate, a negative plate, and the above separator interposed between the positive plate and the negative plate. By using the separator described above, high CCA performance can be ensured while reducing the initial failure rate of the lead-acid battery. By increasing the strength of the separator, it is possible to suppress permeation short circuits or short circuits due to bending of the electrode plates. Therefore, life performance can be improved.

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

In this specification, the vertical direction of a lead-acid battery or components of a lead-acid battery (electrode plate, container, separator, etc.) means the vertical direction of the lead-acid battery when the lead-acid battery is used. Each of the positive electrode plate and the negative electrode plate has an ear portion for connection with an external terminal. there is

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, separators and lead-acid batteries 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.

(separator)
The separator includes a crystalline region in which the molecules of the constituent material of the separator are arranged relatively regularly (that is, highly ordered) and an amorphous region in which the molecules are poorly arranged. Therefore, in the XRD spectrum of the separator, a diffraction peak due to the crystalline region is observed, and scattered light due to the amorphous region is observed as a halo. When the ratio R represented by A ₁ /(A ₁ +A ₂ ) in the XRD spectrum of the separator is 0.60 or more, high strength of the separator can be obtained. Here, A1 is the area of the diffraction peak ( _first diffraction peak) having the maximum peak height among the diffraction peaks corresponding to the crystalline region, and _A2 is the area of the diffraction peak corresponding to the crystalline region. It is the area of the diffraction peak (second diffraction peak) having the second highest peak height.

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 of 2θ from 20° to 22.5°. A diffraction peak corresponding to the (200) plane is observed in the range of 2θ from 23° to 24.5°. A halo in the amorphous region is observed in the range of 2θ from 17° to 27°. Among the diffraction peaks due to the crystalline region, the diffraction peak corresponding to the (110) plane has the highest peak height and corresponds to the first diffraction peak. The diffraction peak corresponding to the (200) plane has the second highest peak height and corresponds to the second diffraction peak.

The ratio R is 0.60 or more, and may be 0.70 or more from the viewpoint of ensuring higher strength of the separator. The ratio R may be 0.90 or less, 0.85 or less, or 0.80 or less. When the ratio R is within such a range, it is easy to secure the flexibility of the separator, and the production is easy.

The ratio R is 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 0.90 or less. It may be 80 or less.

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 equation.

The separator has a first pore volume Vt of 0.8 cm ³ /g or more. By setting the first pore volume Vt within such a range, high diffusibility of the electrolytic solution 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. The first pore volume Vt is preferably 2.0 cm ³ /g or less, more preferably 1.9 cm ³ /g or less, from the viewpoint that the effect of reducing the initial failure rate by increasing the ratio R is more likely to be exhibited. .

The first pore volume Vt is 0.8 cm ³ /g or more and 2.2 cm ³ /g or less (or 2.0 cm ³ /g or less), 0.9 cm ³ /g or more and 2.2 cm ³ /g or less (or 2 0 cm ³ /g or less), 1.0 cm ³ /g or more and 2.2 cm ³ /g or less (or 2.0 cm ³ /g or less), 1.05 cm ³ /g or more and 2.2 cm ³ /g or less (or 2 .0 cm ³ /g or less), 0.8 cm ³ /g or more (or 0.9 cm ³ /g or more), 1.9 cm ³ /g or less, or 1.0 cm ³ /g or more (or 1.05 cm ³ /g or more) ) may be 1.9 cm ³ /g or less.

The separator includes a polymer material (hereinafter also referred to as base polymer). Since the separator contains crystalline regions, the base polymer usually contains a crystalline polymer. The separator includes, for example, polyolefin. A polyolefin is a polymer containing at least olefinic units (that is, a polymer containing at least monomeric units derived from an olefin).

A polyolefin and another base polymer may be used in combination as the base polymer. The ratio of polyolefin to the entire base polymer contained in the separator is, for example, 50% by mass or more, may be 80% by mass or more, or may be 90% by mass or more. The proportion of polyolefin is, for example, 100% by mass or less. The base polymer may consist of polyolefin only. When the ratio of polyolefin is such high, the strength of the separator tends to be low. The defect rate can be kept low.

Polyolefins include, for example, homopolymers of olefins, copolymers containing different olefinic units, and copolymers containing olefinic units and copolymerizable monomeric units. A 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. A copolymerizable monomer unit is a monomer unit derived from a polymerizable monomer other than an olefin and copolymerizable with an olefin.

Polyolefins include, for example, polymers containing at least C _2-3 olefins as monomer units. The C _2-3 olefin includes at least one selected from the group consisting of ethylene and propylene. More preferred polyolefins are, for example, polyethylene, polypropylene, and copolymers containing C _2-3 olefins as monomer units (eg, ethylene-propylene copolymers). Among polyolefins, it is preferable to use polyolefins containing at least ethylene units (polyethylene, ethylene-propylene copolymer, etc.). Polyolefins containing ethylene units (polyethylene, ethylene-propylene copolymers, etc.) may be used in combination with other polyolefins.

The separator preferably contains oil. When the separator contains oil, the effect of suppressing oxidation deterioration of the separator can be further enhanced, which is advantageous in terms of prolonging the life of the separator. Oil refers to a hydrophobic substance that is liquid at room temperature (20° C. or higher and 35° C. or lower) and separates from water. Oils include naturally derived oils, mineral oils, and synthetic oils. Mineral oil, synthetic oil and the like are preferable as the oil. Examples of oils include paraffin oil and silicone oil. The separator may contain one type of oil or may contain two or more types in combination.

The content of oil in the separator may be 11% by mass or more or 12% by mass or more. The oil content may be 18% by mass or less. When the oil content is within this range, the effect of suppressing oxidation deterioration of the separator is enhanced, which is advantageous in terms of prolonging the life of the separator. Also, the resistance of the separator can be kept relatively low.

The separator may be sheet-like. Also, a sheet that is bent into a bellows shape may be used as the separator. The separator may be shaped like a bag. Either one of the positive electrode plate and the negative electrode plate may be wrapped in a bag-shaped separator.

The separator may or may not have ribs. A separator having ribs includes, for example, a base portion and ribs erected 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. In addition, the base portion of the separator is a portion excluding projections such as ribs among constituent portions of the separator, and refers to a sheet-like portion that defines the outer shape of the separator.

The thickness of the separator is, for example, 90 μm or more. From the viewpoint of further reducing the initial failure rate, the thickness is preferably 100 μm or more or 150 μm or more. The thickness of the separator is, for example, 300 μm or less. From the viewpoint of keeping the resistance of the separator low, the thickness of the separator may be 250 μm or less or 200 μm or less. The thickness of the separator means the average thickness of the portion of the separator facing the electrode material. When the separator has a base portion and ribs erected from at least one surface of the base portion, the thickness of the separator is the average thickness of the base portion. When a sticking member (mat, pasting paper, etc.) is stuck to the separator, the thickness of the sticking member is not included in the thickness of the separator.

The thickness of the separator is 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. It may be below.

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

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

For the separator, for example, a resin composition containing a base polymer, a pore-forming agent, and a penetrating agent (surfactant) is extruded into a sheet, stretched, and then at least part of the pore-forming agent is removed. obtained by Removal of at least a portion of the pore-forming agent forms micropores in the matrix of the base polymer. The separator (or the resin composition used for producing the separator) may contain inorganic particles. After removing the pore-forming agent, the sheet-like separator is dried if necessary. For example, the ratio R is adjusted by adjusting at least one selected from the group consisting of the cooling rate of the sheet during extrusion, the draw ratio during stretching, and the temperature during drying. For example, the ratio R tends to increase when the sheet is rapidly cooled during extrusion molding, the draw ratio is increased, or the temperature during drying is decreased. The stretching treatment may be carried out by biaxial stretching, but is usually carried out by uniaxial stretching. The sheet-like separator may be bent into a bellows shape or processed into a bag shape, if necessary.

In separators having ribs, the ribs may be formed into the sheet during extrusion of the resin composition. Alternatively, the ribs may be formed by pressing the sheet with a roller having grooves corresponding to the ribs after molding the resin composition into a sheet or after removing the pore-forming agent.

The pore structure and the first pore volume Vt in the separator control the affinity between the base polymer and the pore-forming agent and/or the penetrating agent, control the dispersibility of the pore-forming agent, and determine the type of inorganic particles. and/or select the particle size, select the type of penetrant, adjust the amount of the inorganic particles, the amount of the pore-forming agent, and/or the amount of the penetrant, and/or the surface of the inorganic particles can be adjusted by adjusting the amount of functional groups and/or atoms present in .

Pore-forming agents include liquid pore-forming agents and solid pore-forming agents. The pore-forming agent preferably contains at least oil. By using oil, an oil-containing separator can be obtained, and the effect of suppressing oxidative deterioration is further enhanced. The pore-forming agents may be used singly 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. At room temperature (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 as a solid pore-forming agent.

As the liquid pore-forming agent, the oils mentioned above are preferred. Solid pore formers include, for example, polymer powders.

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

For example, a separator containing oil is formed by extracting and removing a portion of the oil using a solvent from a sheet formed using oil as a pore-forming agent. A solvent is selected, for example, according to the type of oil. For example, the oil content in the separator can be adjusted by adjusting the type and composition of the solvent, extraction conditions (extraction time, extraction temperature, speed of supplying the solvent, etc.).

Surfactants as penetrants may be, for example, ionic surfactants or nonionic surfactants. Surfactants may be used alone or in combination of two or more.

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 penetrant content in the separator may be 10% by mass or less.

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

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

(separator analysis or size measurement)
(Preparation of separator)
An unused separator or a separator removed from a fully charged lead-acid battery in the initial stage of use is used for analysis or size measurement of the separator. Separators removed from lead-acid batteries are washed and dried prior to analysis or measurement.

The cleaning and drying of the separator removed from the lead-acid battery are performed according to the following procedures. The separator taken out from the lead-acid battery is immersed in pure water for 1 hour to remove the sulfuric acid in the separator. Next, the separator is taken out from the liquid in which it was immersed, left to stand in an environment of 25° C.±5° C. for 16 hours or longer, and dried.

In this specification, the fully charged state of a lead-acid battery is defined by the definition of JIS D 5301:2019. More specifically, the terminal voltage (V ) or the fully charged state is the state in which the electrolyte solution density converted to temperature at 20° C. is charged three times consecutively until it shows a constant value with three significant digits. The numerical value described as the rated capacity is a numerical value whose unit is Ah. The unit of current set based on the numerical value described as the rated capacity is A.

A fully-charged lead-acid battery is a lead-acid battery obtained by fully charging an existing chemical lead-acid battery. The lead-acid battery may be fully charged immediately after the formation as long as it is after the formation, or after some time has passed since the formation. may be used).

In this specification, the term "battery in the early stage of use" means a battery in which not much time has passed since the start of use and which has hardly deteriorated.

(XRD spectrum)
The XRD spectrum of the separator is measured by irradiating X-rays in a direction perpendicular to the surface of the separator. A sample for measurement is produced by processing the portion of the separator facing the electrode material into a strip shape. For separators with ribs, samples are prepared by processing the base portion into strips so as not to include ribs. Measurement and fitting of the XRD spectrum are performed under the following conditions.
(Measurement condition)
Measuring device: RINT-TTR2, manufactured by Rigaku Fitting: FT (step scan) method Measuring angle range: 15-35°
Step width: 0.02°
Measurement speed: 5°/min
XRD data processing: using XRD pattern analysis software (PDXL2, manufactured by Rigaku).

(First pore volume Vt)
A sample (hereinafter referred to as sample A) is prepared by processing the portion of the separator facing the electrode material into a strip of 20 mm×5 mm. In the case of a separator having ribs, sample A is produced by processing the base portion into a strip shape so as not to include ribs. For sample A, the pore size distribution is determined using a mercury porosimeter under the following conditions, and Vt is determined by totaling the volumes of the first pores.
Mercury porosimeter: Autopore IV9510, manufactured by Shimadzu Corporation Pressure range for measurement: 4 psia (≈27.6 kPa) to 60,000 psia (≈414 MPa) Pore distribution: 0.01 μm to 50 μm

(Separator thickness and rib height)
The thickness of the separator is obtained by measuring the thickness at five arbitrarily selected points in a cross-sectional photograph of the separator and averaging the thicknesses.

The height of the rib is obtained by averaging the heights from one surface of the base portion of the rib measured at 10 arbitrarily selected locations of the rib in the cross-sectional photograph of the separator.

(Oil content in separator)
A sample (hereinafter referred to as sample B) 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, Sample B is produced by processing the base portion into a strip shape so as not to include ribs.

About 0.5 g of sample B is taken and weighed accurately to determine the initial sample mass (m0). Place the weighed sample B in an appropriately sized glass beaker and add 50 mL of n-hexane. Next, ultrasonic waves are applied to each beaker for about 30 minutes to elute the oil contained in sample B into n-hexane. Next, a sample is removed from n-hexane, dried in the air at room temperature (20° C. or higher and 35° C. or lower), and weighed to determine the mass (m1) of the sample after oil removal. Then, the oil content is calculated by the following formula. The oil content is determined for 10 samples B, and the average value is calculated. The obtained average value is taken as the oil content in the separator.
Oil content (% by mass) = (m0-m1)/m0 x 100

(Content of inorganic particles in separator)
A portion of sample B prepared in the same manner as described above is sampled, accurately weighed, placed in a platinum crucible, and heated with a Bunsen burner until white smoke is no longer produced. Next, the resulting sample is heated in an electric furnace (550° C.±10° C. in an oxygen stream) for about 1 hour to be ashed, and the ashed matter is weighed. The ratio (percentage) of the mass of the ash to the mass of the sample B is calculated and defined as the inorganic particle content (% by mass). The content of inorganic particles is determined for 10 samples B, and the average value is calculated. Let the obtained average value be the content rate of the inorganic particle in a separator.

(Content of penetrant in separator)
A portion of Sample B prepared in the same manner as described above is sampled, weighed accurately, and dried at room temperature (20° C. or higher and 35° C. or lower) under a reduced pressure environment lower than atmospheric pressure for 12 hours or more. The dried material is placed in a platinum cell, set in a thermogravimetry device, and heated from room temperature to 800° C.±1° C. at a temperature elevation rate of 10 K/min. The amount of weight loss when the temperature is raised from room temperature to 250°C ± 1°C is taken as the mass of the penetrant, and the ratio (percentage) of the mass of the penetrant to the mass of sample B is calculated, and the content of the above penetrant. (% by mass). As a thermogravimetry device, T.I. A. Q5000IR manufactured by Instruments is used. The penetrant content is determined for 10 samples B, and the average value is calculated. The obtained average value is taken as the penetrant content in the separator.

(Positive plate)
A paste-type positive plate is used as the positive plate. The pasted positive plate comprises a positive current collector and a positive electrode material. A positive electrode material is held by a positive current collector. The positive electrode material is a portion of the positive electrode plate excluding the positive current collector. In addition, members such as mats and pasting paper may be attached to the electrode plates. Such a member (also referred to as a sticking member) is included in the electrode plate because it is used integrally with the electrode plate. When the positive electrode plate includes the sticking member, the positive electrode material is the portion of the positive electrode plate excluding the positive current collector and the sticking member.

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. Processing methods include, for example, expanding processing and punching processing. It is preferable to use a grid-like current collector as the positive electrode current collector because it facilitates carrying the positive electrode material.

Pb--Ca alloys and Pb--Ca--Sn alloys are preferable as the lead alloy used for the positive electrode current collector in terms of corrosion resistance and mechanical strength. The positive electrode current collector may have lead alloy layers with different compositions, and the alloy layer may be a single layer or a plurality of layers.

The positive electrode material contained in the positive electrode plate includes a positive electrode active material (lead dioxide or lead sulfate) that develops capacity through an oxidation-reduction reaction. The positive electrode material may contain other additives (such as reinforcing materials) as necessary.

Examples of reinforcing materials include fibers (inorganic fibers, organic fibers, etc.). Examples of resins (or polymers) constituting organic fibers include acrylic resins, polyolefin resins (polypropylene resins, polyethylene resins, etc.), polyester resins (including polyalkylene arylates (polyethylene terephthalate, etc.)). , and celluloses (cellulose, cellulose derivatives (cellulose ether, cellulose ester, etc.)). Celluloses also include rayon.

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

An unformed paste-type positive electrode plate is obtained by filling a positive electrode current collector with a positive electrode paste, followed by aging and drying. The positive electrode paste is prepared by adding water and sulfuric acid to lead powder, an antimony compound, and optionally other additives (reinforcing material, etc.) and kneading them.

A positive electrode plate is obtained by chemically forming an unformed positive electrode plate. Formation can be performed by charging the electrode plate group including the unformed positive electrode plate while immersing the electrode plate group in an electrolytic solution containing sulfuric acid in the battery case of the lead-acid battery. However, formation may be performed before assembly of the lead-acid battery or the electrode plate assembly.

(negative plate)
A negative electrode plate of a lead-acid battery is composed of a negative current collector and a negative electrode material. The negative electrode material is a portion of the negative electrode plate excluding the negative electrode current collector. 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 plate includes the sticking member, the negative electrode material is the portion of the negative plate excluding the negative current collector and the sticking member.

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 an expanding process.

In particular, an electrode plate using a current collector formed by expansion processing is likely to be deformed during the manufacturing process of the electrode plate, and short circuits are likely to occur in the initial stage, so the rate of initial failure tends to increase. According to the above aspect, since the crystallinity of the separator is increased and the strength is improved, the initial failure rate can be reduced even when at least one of the positive electrode plate and the negative electrode plate includes an expanded lattice. .

The lead alloy used for the negative electrode current collector may be any of Pb--Sb-based alloy, Pb--Ca-based alloy, and 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 electrode current collector may have lead alloy layers with different compositions, and the alloy layer may be a single layer or a plurality of layers.

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

Examples of organic shrink-proofing agents include lignin, ligninsulfonic acid, synthetic organic shrink-proofing agents (formaldehyde condensates of phenolic compounds, etc.), and the like. The negative electrode material may contain one kind or two or more kinds of organic expanders.

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

Examples of carbonaceous materials 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 may contain two or more types.

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

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

The reinforcing material includes, for example, fibers (inorganic fibers, organic fibers (eg, organic fibers made of a resin described for the reinforcing material of the positive electrode material), etc.).

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

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

The negative electrode plate can be formed by filling a negative electrode current collector with a negative electrode paste, aging and drying to prepare an unformed negative electrode plate, and then forming the unformed negative electrode plate. The negative electrode paste is prepared by adding water and sulfuric acid to lead powder, an organic anti-shrinking agent, and optionally various additives, and kneading the mixture. In the aging step, the unformed negative electrode plate is preferably aged at a temperature and humidity higher than room temperature.

Formation can be performed by charging the electrode plate group including the unformed negative electrode plate while the electrode plate group is immersed in an electrolytic solution containing sulfuric acid in the battery case of the lead-acid battery. However, formation may be performed before assembly of the lead-acid battery or the electrode plate assembly. Formation produces spongy lead.

(Electrolyte)
The electrolyte is an aqueous solution containing sulfuric acid. The electrolytic solution may be gelled if necessary.

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.

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. It should be noted that these specific gravities are values for the electrolytic solution of a lead-acid battery in a fully charged state.

The method for evaluating each characteristic will be described below.

(1) CCA Performance Based on JIS D 5301:2006, the startability of a lead-acid battery is evaluated according to the current value at which the terminal voltage becomes 7.2 V or higher 30 seconds after the start of discharge, according to the following procedure. A higher current value means a higher startability and a lower resistance of the separator.
(a) Place the storage battery in a cooling room at -18°C ± 1°C for at least 16 hours after full charge is complete.
(b) After confirming that the temperature of the electrolyte in one of the cells in the center is -18°C ± 1°C, discharge with CCA390A for 30 seconds.
(c) Record the terminal voltage 30 seconds after the start of discharge.

(2) Initial short circuit rate (initial failure rate)
(a) Seven unformed negative electrode plates and six unformed positive electrode plates accommodated in bag-like separators are alternately stacked to assemble an electrode plate group having unformed negative electrode plates at both ends. At this time, it is visually confirmed whether or not there is a hole in the separator due to bending of the current collector.
(b) Each of the six electrode plate groups for which holes in the separator could not be confirmed in (a) was accommodated in each cell chamber of a battery case, an electrolytic solution was injected, and a lead-acid battery was subjected to chemical conversion treatment. to make.
(c) The chemically treated lead-acid battery is discharged for 2.5 seconds at a current (A) that is 8.3 times the numerical value in Ah, which is described as the rated capacity. If the voltage after discharge is 9.5 V (1.58 V/cell) or less, it is determined that the discharge is defective.
(d) Total the number of bag-shaped separators confirmed to have holes in (a) and the number of bag-shaped separators confirmed to have holes in the electrode plate group judged to be defective in (c). By doing so, the number n1 of defective bag-shaped separators is obtained.
(e) By dividing the number n1 of bag-shaped separators with defects by the total number N of bag-shaped separators produced, the ratio of bag-shaped separators with defects is obtained, and the initial failure rate (initial battery short circuit percentage) (ppm). The total number N of bag-shaped separators produced is the number of lead-acid batteries produced in (b) (= mass production quantity (eg, 100,000)) and the number of all bag-shaped separators contained in one lead-acid battery (= 7 × 6=42) and the total number of bag-shaped separators included in the electrode plate group including separators for which holes were confirmed in (a).

FIG. 1 shows the appearance of an example of a lead-acid battery according to an embodiment of the present invention.
A lead-acid battery 1 includes a battery case 12 that accommodates an electrode plate group 11 and an electrolytic solution (not shown). The interior of the container 12 is partitioned into a plurality of cell chambers 14 by partition walls 13 . Each cell chamber 14 accommodates one electrode plate group 11 . The opening of the container 12 is closed with 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 rehydrating, the rehydration liquid is replenished by removing the liquid port plug 18. - 特許庁The liquid port plug 18 may have a function of discharging the gas generated inside the cell chamber 14 to the outside of the battery.

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

The matters described in this specification can be combined arbitrarily.

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

<<Lead-acid batteries E1 to E15 and C1 to C9>>
Each lead-acid battery was produced in the following procedure.
(1) Preparation of Separator A resin composition containing 100 parts by mass of polyethylene, about 160 parts by mass of silica particles, about 80 parts by mass of paraffinic oil as a pore-forming agent, and 2 parts by mass of a penetrating agent was prepared into a sheet. A microporous membrane having ribs on one side was produced by extruding the membrane into a single layer, stretching the membrane, and removing part of the pore-forming agent. At this time, the cooling rate and stretching ratio of the extruded sheet were adjusted so that the ratio R of the separator obtained by the above-described procedure was the value shown in Table 1. In addition, the amount of silica particles and the amount of pore-forming agent relative to polyethylene were adjusted so that the first pore volume Vt obtained by the procedure described above was the value shown in Table 1.

The oil content determined by the procedure described above was about 15% by mass, and the silica particle content was 60% by mass. The rib height determined by the procedure described above was 0.6 mm. The thickness of the separator (thickness of the base portion) determined by the above procedure was 0.2 mm.

Next, the sheet-like microporous membrane was folded in two so that ribs were arranged on the outer surface to form a bag, and the overlapped ends were crimped to obtain a bag-like separator.

The ratio R of the separator, the first pore volume Vt, the oil content, the silica particle content, the thickness of the base portion, and the height of the rib are the values obtained for the separator before the production of the lead-acid battery. However, it is almost the same as the value measured by the above-described procedure for the separator taken out from the manufactured lead-acid battery.

(2) Production of positive electrode plate A positive electrode paste was prepared by mixing lead oxide, reinforcing material (synthetic resin fiber), water and sulfuric acid. The positive electrode paste was filled in the mesh part of an expanded lattice made of a Pb-Ca-Sn alloy containing no antimony, and then aged and dried to obtain an unformed unformed grid with a width of 100 mm, a height of 110 mm, and a thickness of 1.6 mm. A positive plate was obtained.

(3) Preparation 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 in the mesh part of an expanded lattice made of a Pb-Ca-Sn alloy containing no antimony, and then aged and dried to obtain an unformed unformed grid with a width of 100 mm, a height of 110 mm, and a thickness of 1.3 mm. A negative plate was obtained. The amounts of carbon black, barium sulfate, lignin and synthetic resin fiber used were such that the content of each component in the negative electrode plate taken out from a fully charged lead-acid battery was 0.3% by mass, 2.1% by mass and 0.3% by mass, respectively. It was adjusted to be 1% by mass and 0.1% by mass.

(4) Preparation of lead-acid battery An unchemically formed negative electrode plate was placed in a bag-like separator and laminated with a positive electrode plate to form an electrode plate group with seven unchemically formed negative electrode plates and six unchemically formed positive electrode plates. .

The ears of the positive electrode plate and the ears of the negative electrode plate were welded to the shelf of the positive electrode and the shelf of the negative electrode by a cast-on-strap (COS) method, respectively. The electrode plate group is inserted into a polypropylene battery case, the electrolyte is injected, and chemical conversion is performed in the battery case so that the rated voltage is 12 V and the rated capacity is 30 Ah (5 hour rate capacity (Ah described in the rated capacity). A liquid lead-acid battery with a capacity when discharged at a current (A) that is 1/5 of the value of )) was assembled. Six electrode plate groups are connected in series in the container.

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

(5) Evaluation FIG. 2 shows the XRD spectrum of the separator of Example 1 measured by the procedure described above. As shown in FIG. 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 the diffraction peak corresponding to the (200) plane was observed. A peak was observed in the range 2θ=23° to 24.5°. A broad halo due to the amorphous region was observed over a wide range of 2θ=17° to 27°.

Using the obtained lead-acid battery, the CCA performance and the initial failure rate were evaluated by the procedure described above. The CCA performance was evaluated by the ratio (%) of the terminal voltage at 30 seconds of each lead-acid battery when the terminal voltage at 30 seconds of lead-acid battery C1 was defined as 100.

Evaluation results are shown in Table 1 and FIG. E1 to E15 in Table 1 are examples. C1-C9 are comparative examples.

As shown in Table 1 and FIG. 3, high CCA performance can be ensured regardless of the ratio R when the first pore volume Vt is 0.8 cm ³ /g or more. 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 There is a tendency for the failure rate to decrease (compare C1 with C2 to C6). On the other hand, when the ratio R is 0.60 or more, the initial failure rate can be greatly reduced even when the first pore volume Vt is 0.8 cm ³ /g or more. It is considered that this is because the strength of the separator is improved by increasing the crystallinity of the separator.

The lead-acid battery separator according to the above aspect of the present invention is suitable, for example, for IS applications (lead-acid batteries for ISS vehicles, etc.), starting power sources for various vehicles (automobiles, motorcycles, etc.). In addition, the lead-acid battery separator can be suitably used as a power source for industrial power storage devices such as electric vehicles (forklifts, etc.). It should be noted that these uses are merely exemplary. Applications of the lead-acid battery separator and the lead-acid battery according to the above aspects of the present invention are not limited to these.

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

Claims (8)

A lead-acid battery separator,
the separator includes a crystalline region and an amorphous region;
In the X-ray diffraction spectrum of the separator, the ratio R represented by A ₁ /(A ₁ +A ₂ ) is 0.60 or more,
A ₁ is the area of the first diffraction peak having the maximum peak height among the diffraction peaks corresponding to the crystalline region,
_A2 is the area of the second diffraction peak with the second highest peak height among the diffraction peaks corresponding to the crystalline region,
A separator for a lead-acid battery, wherein 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. 2. The lead-acid battery separator according to claim 1, wherein said ratio R is 0.70 or more. 3. The lead-acid battery separator according to claim 1, wherein the total volume Vt is 1.0 cm< ³ >/g or more. The lead-acid battery separator according to any one of claims 1 to 3, comprising polyolefin. The polyolefin contains at least ethylene units,
the first diffraction peak corresponds to the (110) plane of the crystalline region;
5. The lead-acid battery separator according to claim 4, wherein said second diffraction peak corresponds to the (200) plane of said crystalline region. The lead-acid battery separator according to any one of claims 1 to 5, having a thickness of 100 µm or more and 300 µm or less. The lead-acid battery separator according to any one of claims 1 to 6, which contains oil. A lead-acid battery,
The lead-acid battery includes at least one cell including an electrode group and an electrolyte,
The electrode plate group includes a positive electrode plate, a negative electrode plate, and a separator interposed between the positive electrode plate and the negative electrode plate,
A lead-acid battery, wherein the separator is the lead-acid battery separator according to any one of claims 1 to 7.

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