JP6714973B2 - Separator for water-based electrolyte storage battery, and water-based electrolyte storage battery using the same - Google Patents

Description

The present invention relates to an aqueous electrolyte storage battery separator and an aqueous electrolyte storage battery using the same.

In recent years, with the diversification of electronic devices, higher performance has been demanded for various storage batteries. Of these storage batteries using aqueous electrolyte is present in a wide variety of lead-acid batteries using sulfuric acid aqueous, nickel-cadmium batteries that use A alkaline aqueous systems include alkaline batteries such as nickel-hydrogen batteries, high capacity, Longer life and smaller size are required.

Nonwoven fabrics, microporous membranes, etc. have been widely used as storage battery separators. The functions of the separator are physical contact between electrodes, electrical insulation to prevent short circuit, excellent wettability to electrolyte, excellent liquid retention, and chemical stability to electrolyte. It has, has an appropriate strength, and the like. For example, in alkaline battery separators, a polyolefin-based wet non-woven fabric is used.

In Patent Document 1 below, “(1) fiber diameter is 3 μm or less, ultrafine fibers, (2) fiber diameter (circular conversion value) is 3 to 5 μm (3 μm is not included), and cross-sectional shape is non-circular. A quasi-ultrafine shaped fiber, and (3) a composite high-strength polypropylene fiber having a tensile strength of 4.5 cN/dtex or more, which is provided with a fusion component on the surface, and the fusion component of the composite high-strength polypropylene fiber Is a battery separator containing a fused non-woven fabric, wherein the separator has a maximum pore diameter of 25 μm or less.

In addition, in Patent Document 2 below, "an alkaline battery separator comprising a wet-laid nonwoven fabric having a multilayer structure composed of an alkali-resistant cellulose fiber, an alkali-resistant synthetic fiber, and a binder component, wherein the wet-laid nonwoven fabric has an average pore diameter Of 10 μm or less” is disclosed.

Japanese Patent No. 5006546 JP, 2014-26877, A

However, the battery separator described in Patent Document 1 is a battery separator containing a polypropylene-based nonwoven fabric and has one of the characteristics that the maximum pore size is 25 μm or less, but there is no description about the minimum pore size. According to the study by the inventors of the present application, if the pore size of the nonwoven fabric is too small, the nonwoven fabric becomes too dense and the ion permeability deteriorates, so that the internal resistance increases, and the capacity retention ratio, which is considered to affect the ion permeability, also decreases. It became clear to do. Further, since the non-woven fabric used in the battery separator described in Patent Document 1 is a short fiber non-woven fabric formed by a wet method, the present inventors have found that the base fabric strength in the electrolytic solution is unstable. Therefore, it has been found that it is difficult to maintain the battery characteristics and the cycle life tends to be shortened against physical vibration, environmental changes, and temporal changes.

Further, the battery separator described in Patent Document 2 is a short fiber non-woven fabric formed by a wet method, and by including a fusion component, a binder component, etc., is excellent in dimensional stability in an electrolytic solution and is excellent. Although it is described as a dense separator exhibiting ion permeability, the fusion component, the binder component, etc. are eluted into the electrolytic solution after a long time, which shortens the cycle life of the storage battery. It became clear by the examination of the people.

Under such circumstances, the problems to be solved by the present invention include excellent ion permeability, wettability and liquid retention of an electrolytic solution, and a separator for an aqueous electrolyte battery having electrical insulation, and high capacity and low capacity. An object of the present invention is to provide a water-based electrolytic solution storage battery having resistance, long cycle life, and high reliability.

As a result of intensive studies and experiments to solve the above problems, the inventors of the present invention unexpectedly found that the above problems can be solved by the following constitutions, and completed the present invention. .. That is, the present invention is as follows.
[1] The following formulas (1) to (4):
Dmax≦20 μm. ． ． (1)
0.1 μm≦Dmin. ． ． (2)
Dmax/Dave<3.00. ． ． (3)
Dmax/Dmin<5.00. ． ． (4)
{In the formula, Dmax is the maximum pore diameter (μm), Dave is the average pore diameter (μm), and Dmin is the minimum pore diameter (μm). ] A lead-acid battery composed of a non-woven fabric having a pore size distribution satisfying the following conditions and having an average fiber diameter of 0.1 μm or more and 5.0 μm or less and a fiber length of 150 mm or more, and having a formation variation coefficient of 100 or less. Alternatively, a separator for an aqueous electrolyte storage battery, which is either an alkaline battery.
[2] The separator for an aqueous electrolyte storage battery according to [1], wherein the nonwoven fabric has an average pore diameter (Dave) of 10 μm or less.
[3] The separator for an aqueous electrolyte storage battery according to the above [1] or [2], wherein the nonwoven fabric has a minimum pore diameter (Dmin) of 5 μm or less.
[4] The separator for an aqueous electrolyte storage battery according to any of [1] to [3], wherein the non-woven fabric is a non-woven fabric composed of thermoplastic resin fibers.
[5] The separator for an aqueous electrolyte storage battery according to any of [1] to [4], wherein the nonwoven fabric is a hydrophilically treated nonwoven fabric.
[6] The separator for an aqueous electrolyte storage battery according to any one of [1] to [5], wherein the nonwoven fabric has a thickness of 10 to 300 μm and a basis weight of 5 to 100 g/m ² .
[7] The separator for an aqueous electrolyte storage battery according to any of [1] to [6], wherein the nonwoven fabric has a porosity of 30 to 95%.
[8] A laminated non-woven fabric having at least two non-woven fabric layers in which a non-woven fabric is further laminated on the non-woven fabric , the following formulas (1) to (4):
Dmax≦20 μm. ． ． (1)
0.1 μm≦Dmin. ． ． (2)
Dmax/Dave<3.00. ． ． (3)
Dmax/Dmin<5.00. ． ． (4)
{In the formula, Dmax is the maximum pore diameter (μm), Dave is the average pore diameter (μm), and Dmin is the minimum pore diameter (μm). } The pore size distribution which satisfy|fills}, and the formation variation coefficient is 100 or less, and is comprised, The separator for aqueous electrolyte storage batteries in any one of said [1]-[7].
[9] The separator for an aqueous electrolyte storage battery according to any one of [1] to [8], wherein the nonwoven fabric is a calendered nonwoven fabric or a laminated nonwoven fabric.
[10] A water-based electrolyte storage battery having the water-based electrolyte storage battery separator according to any one of [1] to [9].
[11] An alkaline secondary battery including the separator for an aqueous electrolyte solution storage battery according to any one of [1] to [9].

Since the pore size distribution of the separator for an aqueous electrolyte storage battery of the present invention is highly controlled, it has excellent ion permeability, liquid retention, electrical insulation, and chemical stability. Further, the water-based electrolyte storage battery of the present invention, by having the separator for the water-based electrolyte storage battery of the present invention, in a stable production process, good yield, can be produced at low cost, high capacity and low resistance, cycle Long life and high reliability. It should be noted that the above description does not disclose all the embodiments of the present invention and all advantages related to the present invention.

Hereinafter, more detailed description will be given for the purpose of illustrating representative embodiments of the present invention, but the present invention is not limited to these embodiments.
The separator for an aqueous electrolyte storage battery of the present embodiment has the following formulas (1) to (4):
Dmax≦20 μm. ． ． (1)
0.1 μm≦Dmin. ． ． (2)
Dmax/Dave<3.00. ． ． (3)
Dmax/Dmin<5.00. ． ． (4)
{In the formula, Dmax is the maximum pore diameter (μm), Dave is the average pore diameter (μm), and Dmin is the minimum pore diameter (μm). } It is a separator for water-based electrolyte solution storage batteries comprised from the nonwoven fabric which has the pore size distribution which satisfy|fills.

The maximum pore diameter (Dmax) of the nonwoven fabric that constitutes the separator for an aqueous electrolyte storage battery of the present embodiment is 20 μm or less. When the maximum pore diameter is 20 μm or less, the possibility of short circuit can be reduced. The upper limit of the maximum pore diameter (Dmax) may be 20 μm or less, and from the viewpoint of reducing the possibility of short circuit, it is preferably 18 μm or less, 15 μm or less, 10 μm or less, or 5 μm or less. The lower limit of the maximum pore diameter (Dmax) is not limited, but from the viewpoint of electrolyte impregnation and ion permeability, for example, it can be 1 μm or more, 2 μm or more, or 3 μm or more. The range of the maximum pore diameter (Dmax) can be, for example, 1 μm or more and 20 μm or less, preferably 2 μm or more and 18 μm or less, and more preferably 3 μm or more and 15 μm or less.

The minimum pore diameter (Dmin) of the nonwoven fabric that constitutes the separator for an aqueous electrolyte storage battery of the present embodiment is 0.1 μm or more. When the minimum pore diameter is 0.1 μm or more, the ion permeability is good, the internal resistance is low, and the capacity retention ratio, which is considered to affect the ion permeability, is improved. The lower limit of the minimum pore diameter (Dmin) may be 0.1 μm or more, and is preferably 0.3 μm or more, 0.5 μm or more, or 1.0 μm or more from the viewpoint of electrolyte impregnation property and ion permeability. be able to. The upper limit of the minimum pore diameter (Dmin) is not limited, but from the viewpoint of reducing the possibility of short circuit, for example, it can be 5 μm or less, 4 μm or less, 3 μm or less, or 2 μm or less. The range of the minimum pore diameter (Dmin) can be, for example, 0.1 μm or more and 5 μm or less, preferably 0.3 μm or more and 4 μm or less, and more preferably 1 μm or more and 3 μm or less.

The average pore diameter (Dave) of the nonwoven fabric that constitutes the separator for an aqueous electrolyte storage battery of the present embodiment is preferably 10 μm or less. When it is 10 μm or less, the possibility of short circuit can be reduced. The upper limit of the average pore diameter (Dave) may be 10 μm or less, and from the viewpoint of more effectively reducing the possibility of short circuit, for example, 8 μm or less, 5 μm or less, 4 μm or less, 3 μm or less, or 2 μm or less. be able to. The lower limit of the average pore diameter (Dave) is not limited, but from the viewpoint of electrolyte impregnation and ion permeability, for example, 0.1 μm or more, 0.5 μm or more, 1.0 μm or more, 1.5 μm or more, or 2 It can be 0.0 μm or more.

The ratio (Dmax/Dave) of the maximum pore diameter (Dmax) to the average pore diameter (Dave) of the nonwoven fabric that constitutes the separator for an aqueous electrolyte solution storage battery of this embodiment is less than 3.00. When Dmax/Dave is less than 3.00, the pore size distribution becomes uniform, the ion permeability in the separator becomes uniform, and the capacity retention rate and the possibility of short circuit due to partial precipitation are reduced. can do. The upper limit of Dmax/Dave may be less than 3.00, and is less than 2.75, less than 2.50, and less than 2.50 from the viewpoint of more effectively reducing the possibility of a decrease in capacity retention rate and short circuit. It can be less than 10, less than 2.00, less than 1.90, less than 1.80, or less than 1.70.

The ratio (Dmax/Dmin) of the maximum pore diameter (Dmax) to the minimum pore diameter (Dmin) of the nonwoven fabric that constitutes the separator for an aqueous electrolyte solution storage battery of the present embodiment is less than 5.00. When it is less than 5.00, the pore size distribution becomes uniform, and the reduction in capacity retention rate and the possibility of short circuit can be reduced. The upper limit of Dmax/Dmin may be less than 5.00, and is less than 4.50, less than 4.25, 4.00 from the viewpoint of more effectively reducing the possibility of a decrease in capacity retention rate and short circuit. Can be less than, less than 3.50, or less than 3.00.

In the separator for a water-based electrolyte storage battery of the present embodiment, it is preferable that the nonwoven fabric is made of ultrafine fibers having an average fiber diameter of 0.1 μm or more and 5.0 μm or less. When the thickness is 0.1 μm or more, the strength of the nonwoven fabric becomes high and it does not become too dense, so that the permeability of the electrolytic solution and the ion permeability are good, and the internal resistance can be lowered. On the other hand, when the thickness is 5.0 μm or less, local variations in the compactness are reduced, excellent electrical insulation can be obtained, and the possibility of short circuit can be reduced. The average fiber diameter of the ultrafine fibers may be, for example, 0.2 μm or more and 3 μm or less, 0.3 μm or more and 2 μm or less, 0.3 μm or more and 2.5 μm or less, or 0.3 μm or more and 2.0 μm or less.

In the separator for an aqueous electrolyte storage battery of the present embodiment, it is preferable that the non-woven fabric is made of ultrafine fibers having a fiber length of 150 mm or more. When the fiber length of the ultrafine fibers is 150 mm or more, the strength and processability of the nonwoven fabric are improved. More preferably, the fiber length of the ultrafine fibers is 200 mm or more.

In the separator for an aqueous electrolyte storage battery of the present embodiment, it is preferable that the non-woven fabric is composed of continuous long fibers. In the present specification, the continuous continuous fiber refers to a fiber defined by JIS-L0222. In the separator for a water-based electrolyte storage battery of the present embodiment, it is more preferable that the non-woven fabric is composed of continuous filaments of ultrafine fibers.

In the separator for a water-based electrolyte storage battery of the present embodiment, it is preferable that the non-woven fabric is composed of thermoplastic resin fibers. The thermoplastic resin is not limited, polyolefin resin, polyester resin, polyamide resin, polyphenylene sulfide resin, polyvinyl chloride, polyimide, ethylene vinyl acetate copolymer, polyacrylonitrile, polycarbonate, polystyrene, ionomer, Included are polyphenylene sulfide (PPS), and mixtures thereof. Examples of the polyolefin resin include homopolymers or copolymers of α-olefins such as ethylene, propylene, 1-butene, 1-hexene, 4-methyl-1-pentene and 1-octene; high pressure low density polyethylene. , Linear low density polyethylene (LLDPE), high density polyethylene, polypropylene (propylene homopolymer), polypropylene random copolymer, poly 1-butene, poly 4-methyl-1-pentene, ethylene/propylene random copolymer, Examples thereof include ethylene-1-butene random copolymer and propylene-1-butene random copolymer. Examples of polyester resins include polyethylene terephthalate (PET), polybutylene terephthalate, and polyethylene naphthalate. Examples of the polyamide-based resin include nylon-6 (Ny), nylon-66, polymeta-xylene adipamide and the like.

The thermoplastic resin fiber is preferably polypropylene (PP), nylon-6 (Ny), polyphenylene sulfide (PPS), and polyethylene terephthalate from the viewpoints of electrolyte permeability, chemical stability, electrical insulation, and the like. It is at least one selected from the group consisting of (PET). Among them, the thermoplastic resin fiber is preferably at least one selected from the group consisting of polypropylene (PP) and nylon-6 (Ny) from the viewpoint of solution resistance.

In the aqueous electrolyte storage battery separator of the present embodiment, it is preferable that the nonwoven fabric is subjected to hydrophilic treatment. When the non-woven fabric is hydrophilized, it becomes easier to impregnate the voids of the non-woven fabric with the electrolytic solution, so more electrolyte can be taken into the separator, and the ion permeability and liquid retention of the electrolytic solution can be improved. It is preferable because it is possible to provide an excellent separator for a water-based electrolyte storage battery, which can be used to provide a higher-performance water-based electrolyte storage battery. Examples of the hydrophilic treatment method include a physical treatment method, for example, hydrophilic treatment by corona treatment or plasma treatment; and a chemical treatment method, for example, introduction of a surface functional group, for example, sulfonic acid group or carboxylic acid by oxidative treatment. Introducing a group or the like; a water-soluble polymer such as PVA, polystyrene sulfonic acid, or polyglutamic acid, and/or a surfactant such as a nonionic surfactant, an anionic surfactant, a cationic surfactant. Processing with a treatment agent such as an activator or a zwitterionic surfactant can be employed. A person skilled in the art can select an appropriate hydrophilization processing method and conditions, for example, the usage amount of the treating agent and the introduction amount of the functional group in consideration of the affinity with the electrolytic solution.

In the aqueous electrolyte storage battery separator of the present embodiment, the thickness of the nonwoven fabric is preferably 10 to 300 μm. When the thickness of the non-woven fabric is in this range, the strength, handling property and electric resistance value of the non-woven fabric can be further reduced, which is preferable. The thickness of the non-woven fabric can be, for example, 20 to 250 μm, 30 to 225 μm, 40 to 200 μm, 50 to 200 μm, or more than 50 to 200 μm.

In the separator for an aqueous electrolyte storage battery of the present embodiment, the basis weight of the nonwoven fabric is preferably 5 to 100 g/m ² . When the basis weight of the nonwoven fabric is within this range, it is preferable from the viewpoint of strength, electric resistance value, ion permeability and the like of the nonwoven fabric. The basis weight of the nonwoven fabric can be, for example, 7 to 90 g/m ² , 10 to 80 g/m ² , or 10 to 50 g/m ² .

In the separator for a water-based electrolyte storage battery of the present embodiment, it is preferable that the non-woven fabric has a porosity of 30 to 95%. When the porosity of the non-woven fabric is in this range, it is preferable from the viewpoint of permeability of the electrolytic solution, ion permeability, liquid retention amount, cycle life, and prevention of short circuit. The porosity of the nonwoven fabric may be, for example, 40 to 90%, 45 to 85%, 50 to 80%.

In the separator for a water-based electrolyte storage battery of the present embodiment, it is preferable that the formation coefficient of the nonwoven fabric is 100 or less from the viewpoints of separator unevenness, prevention of short circuit, stability of battery performance, reduction of defective rate and the like. The formation coefficient of the non-woven fabric can be, for example, 90 or less, 80 or less, 70 or less, or 60 or less.

The separator for a water-based electrolyte storage battery of the present embodiment preferably has a non-woven fabric suction height of 10 mm or more from the viewpoint of the electrolyte impregnation property and the battery capacity. The suction height of the nonwoven fabric can be, for example, 30 mm or more, 50 mm or more, 60 mm or more, or 70 mm or more.

From the viewpoint of capacity characteristics and cycle life, the separator for an aqueous electrolyte storage battery of the present embodiment preferably has a liquid retaining property of 150% or more. The liquid retention of the non-woven fabric can be, for example, 200% or more, 250% or more, or 300% or more.

In the separator for an aqueous electrolyte storage battery of the present embodiment, it is preferable that the nonwoven fabric has a tensile strength of 3 N/15 mm or more from the viewpoints of handling property, reduction of defective rate and the like. The tensile strength of the nonwoven fabric can be, for example, 5 N/15 mm or more, 6 N/15 mm or more, 7 N/15 mm or more, or 10 N/15 mm or more.

In the separator for an aqueous electrolyte storage battery of the present embodiment, it is preferable that the volume resistance of the non-woven fabric is 1.0×10 ⁸ Ω·cm or more from the viewpoint of prevention of short circuit and the like. The volume resistance of the non-woven fabric is, for example, 1.0×10 ¹⁰ Ω·cm or more, 1.0×10 ¹³ Ω·cm or more, 1.0×10 ¹⁴ Ω·cm or more, or 1.0×10 ¹⁵ Ω·. It can be not less than cm.

In the aqueous electrolyte storage battery separator of the present embodiment, it is preferable that the nonwoven fabric is formed by a melt blow method. The melt-blowing method generally involves sending a molten thermoplastic resin to a melt-blown spinneret, discharging a plurality of spinneret nozzle holes from one or a plurality of spinneret nozzle holes arranged in a row, and forming a row of spinneret nozzle holes. The fibers are thinned by being pulled by the high-speed and high-speed spinning gas ejected from the air gap provided so as to sandwich the fiber. Then, by collecting the fine fibers on a collector net having a suction fan at the bottom, an extremely fine and uniform meltblown nonwoven fabric can be manufactured. By adopting the melt blow method, it becomes easy to achieve a highly controlled pore distribution in the separator for an aqueous electrolyte storage battery of the present embodiment.

The separator for an aqueous electrolyte solution storage battery of the present embodiment may be a laminated non-woven fabric composed of two or more non-woven fabrics. As a constitution of the laminated nonwoven fabric, a laminated body obtained by laminating a meltblown nonwoven fabric on a spunbonded nonwoven fabric (hereinafter also referred to as SM), a laminated body in which a meltblown nonwoven fabric is sandwiched between two spunbonded nonwoven fabric layers (hereinafter, SMS). Will also be referred to as). By stacking the non-woven fabrics, it becomes possible to improve the dispersibility and uniformity of the non-woven fabrics and reinforce the strength. As the constitution of the laminated non-woven fabric other than SM and SMS, for example, a constitution in which a knitted fabric, a woven fabric, a film, an inorganic composite material layer and the like are laminated on the non-woven fabric; Examples include a structure in which spun nonwoven fabric, opened nonwoven fabric, and the like are laminated. As a method for laminating, heat embossing, heat fusion method such as ultrasonic fusion, mechanical entanglement method such as needle punch and water jet, hot melt adhesive, method using adhesive such as urethane adhesive, extrusion Various known methods such as laminating can be adopted.

The nonwoven fabric that constitutes the separator for an aqueous electrolyte storage battery of the present embodiment is preferably a calendered nonwoven fabric. A non-woven fabric can be favorably formed by heat-bonding the fibers in the non-woven fabric layer by calendering. Examples of calendering include a method in which a non-woven fabric layer is pressure-bonded with a hot roll. This method can be carried out in a continuously integrated production line, and is suitable for the purpose of obtaining a uniform non-woven fabric with a low basis weight. .. The heat-bonding step can be performed, for example, at a temperature 50° C. to 120° C. lower than the melting point of the thermoplastic resin and a linear pressure of 100 to 1000 N/cm. The linear pressure in the calendering is preferably in the above range from the viewpoint of the strength of the nonwoven fabric, the reduction of the deformation of the fibers, the reduction of the apparent density, etc., and the highly controlled pores in the separator for the aqueous electrolyte storage battery of the present embodiment. Distribution is easier to achieve.

The hot roll used in calendering may be a roll having an uneven surface, such as an embossed or satin finished pattern, or a smooth flat roll. The surface pattern of the roll having irregularities on the surface is not limited as long as the fibers can be bonded by heat, such as an embossed pattern, a satin pattern, a rectangular pattern, and a line pattern.

The nonwoven fabric that constitutes the separator for an aqueous electrolyte storage battery of the present embodiment may have an inorganic composite material layer on the nonwoven fabric. When the inorganic composite material layer is provided on the nonwoven fabric, the possibility of short circuit can be further reduced. The inorganic composite material layer may contain inorganic particles. As the inorganic composite material layer, a porous layer containing a material capable of closing the pores of the inorganic composite material layer by melting at a predetermined temperature can be used. The porous layer can be provided, for example, as a porous planar structure on the nonwoven fabric. Examples of the method of combining the inorganic material with the non-woven fabric include a method of impregnating the non-woven fabric with a slurry containing inorganic particles, and coating such as transfer.

Examples of the inorganic particles include oxide particles of Al, Si, and/or Zr element having an average particle diameter of 0.5 to 10 μm, and specific examples thereof include iron oxide, SiO ₂ (silica), and Al. ₂ O _{3 (alumina)} oxide particles such as TiO 2, BaTiO _2, ZrO; aluminum nitride, nitrides microparticles such as silicon nitride; calcium fluoride, barium fluoride, poorly soluble ionic crystal fine particles such as barium sulfate; Fine particles of covalent bond such as silicon and diamond; Fine particles of clay such as talc and montmorillonite; Mineral resource-derived substances such as boehmite, zeolite, apatite, kaolin, mullite, spinel, olivine, sericite, bentonite, mica or their artificial products And the like, and these can be used alone or in combination. Examples of the inorganic particles include metal particles; oxide particles such as SnO ₂ and tin-indium oxide (ITO); carbonaceous particles such as carbon black and graphite; The particles may be electrically insulating by being coated with a material having a property (for example, a material forming the above-mentioned non-electrically conductive inorganic particles).

The formation of the inorganic composite material layer can be performed by preparing a slurry in which inorganic particles, a binder, heat-meltable fine particles, etc. are dispersed/dissolved in a solvent, and applying the obtained slurry onto a non-woven fabric and drying. .. The solvent may be any one that can uniformly disperse the inorganic fine particles and the heat-meltable fine particles, and can also dissolve or disperse the binder uniformly. For example, aromatic hydrocarbons such as toluene, methyl ethyl ketone, methyl isobutyl ketone, etc. Organic solvents such as ketones may be used. Water may be used as a solvent when the binder is water-soluble or when it is used as an emulsion. The interfacial tension may be controlled by adding alcohols or propylene oxide-based glycol ethers to these solvents.

The separator for an aqueous electrolyte storage battery of the present embodiment can be used as a separator for an aqueous electrolyte storage battery, for example, an alkaline secondary battery.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Hereinafter, unless otherwise specified, the length direction of the nonwoven fabric is the MD direction (machine direction), and the width direction is the direction perpendicular to the length direction.

[Example 1]
A non-woven fabric was produced by the following melt blow method (MB). Polypropylene (PP) resin was used as the fiber material. A polypropylene (PP) resin melted by an extruder was extruded from a spinneret having a spinneret diameter of 0.30 mm. Continuous long fibers of polypropylene (PP) ultrafine fibers are obtained by appropriately selecting the melting temperature of the polypropylene (PP) resin in the extruder, the spinning gas temperature, the single-hole discharge amount of the molten resin, and pulling and thinning the thermoplastic resin. A meltblown nonwoven fabric (PP-MB) composed of Furthermore, the thickness and the apparent density were adjusted with an embossing roll so as to have a desired thickness, and a PP-MB nonwoven fabric was produced. The obtained PP-MB non-woven fabric was subjected to hydrophilic processing by plasma processing to produce the separator of Example 1. The plasma treatment was performed by reducing the pressure in the plasma treatment apparatus to 10 to 5 Torr and then supplying oxygen gas at a flow rate of 10 cc/min.

[Examples 2 to 17]
As shown in Table 1 below, by changing the fiber material, non-woven fabric composition, etc., and by appropriately selecting the single hole discharge rate, line speed, and spinning gas conditions, various basis weights, apparent densities, etc. can be obtained. The separators of Examples 2 to 17 composed of continuous filaments of ultrafine fibers were produced.

In Example 7, the obtained PP-MB non-woven fabric was subjected to a sulfonation treatment to give a hydrophilic treatment. The sulfonation treatment was carried out in dry air containing sulfur trioxide gas until the sulfur content of the nonwoven fabric reached 0.25% by mass.

In Example 8, the web was laminated directly on the continuous long-fiber nonwoven fabric (fiber diameter: 15 μm) produced by the spunbond method by the same melt-blowing method as described above to form a PP-SM structure. Furthermore, the PP-SM structure was obtained by integrating with an embossing roll and adjusting the thickness and apparent density so as to obtain a desired thickness.

In Examples 13, 14, and 17, the continuous long-fiber nonwoven fabric (fiber diameter: 15 μm) produced by the spunbond method was directly laminated with the web by the same melt-blowing method as described above, and then the spunbond method was used. A continuous long fiber nonwoven fabric (fiber diameter 15 μm) was laminated to obtain a Ny-SMS structure, a PPS-SMS structure, or a PET-SMS structure. Further, they were integrated with an embossing roll, and the thickness and apparent density were adjusted so as to obtain a desired thickness, to obtain each laminated nonwoven fabric.

In Example 17, after producing a PET-SMS nonwoven fabric, the slurry of the following method was applied and dried at 100° C. to produce the separator of Example 17. The slurry was prepared by adding 1000 g of water, 1000 g of spherical silica as inorganic particles, and SBR latex as a binder to a container such that the SBR solid content was 3 parts by mass with respect to 100 parts by mass of spherical silica, and stirring with a three-one motor for 1 hour. It was obtained by dispersing. Application of the slurry was performed by pulling a nonwoven fabric through the slurry.

[Comparative Example 1]
Using polypropylene (PP) (manufactured by Nippon Polypro), by the spunbond method (SB), at a spinning temperature of 300° C., filament filaments are extruded onto a moving collection net at a spinning speed of 4500 m/min. The fiber was spun, charged to about 3 μC/g by corona charging, and sufficiently opened to form a PP-SB long fiber web on the collecting net. After thermally bonding the obtained PP-SB long fiber web with a flat roll, corona discharge machining was carried out, and the calender roll was used to adjust the thickness to a desired thickness and to adjust the apparent density. A separator of Comparative Example 1 was produced.

[Comparative Example 2]
A polypropylene (PP) short fiber having a fiber diameter of 8.5 μm and a fiber length of 5 mm was collected on a net by a papermaking method so as to have a basis weight of 50 g/m ² to obtain a web. The web was dehydrated and dried, and then thermocompression-bonded with a calender roll to prepare a separator of Comparative Example 2.

[Comparative Example 3]
A separator of Comparative Example 3 was produced in the same manner as in Comparative Example 2 except that cellulose (Cel) short fibers having a fiber diameter of 5.3 μm and a fiber length of 5 mm were used and the basis weight was 80 g/m ² .

(1) Measurement of average fiber diameter (μm) of ultrafine fibers A nonwoven fabric was cut into 10 cm×10 cm, pressed on an iron plate at 60° C. above and below at a pressure of 0.30 MPa for 90 seconds, and then the nonwoven fabric was vapor-deposited with platinum. An SEM device (JSM-6510 manufactured by JEOL Ltd.) was used to take an image under the conditions of an accelerating voltage of 15 kV and a working distance of 21 mm. The photographing magnification was 10,000 times for yarns having an average fiber diameter of less than 0.5 μm, 6000 times for yarns having an average fiber diameter of 0.5 μm or more and less than 1.5 μm, and 4000 times for yarns having an average fiber diameter of 1.5 μm or more. The imaging field of view at each imaging magnification was 12.7 μm×9.3 μm at 10000×, 21.1 μm×15.9 μm at 6000×, and 31.7 μm×23.9 μm at 4000×. 100 or more fibers were photographed at random and all fiber diameters were measured. However, the fibers fused in the yarn length direction were excluded from the measurement target. The following formula:
Dw=ΣWi·Di=Σ(Ni·Di ² )/(Ni·Di)
{Wherein Wi=weight fraction of fiber diameter Di=Ni·Di/ΣNi·Di. }, and the weight average fiber diameter (Dw) determined as the average fiber diameter (μm).

A non-woven fabric was produced by producing a single-hole spinneret having only one hole and using a single-hole spinneret to photograph the behavior of the yarn during spinning in the area of the present invention with a high-speed camera. It was confirmed that the constituent fibers were continuous long fibers. In the conventional melt blown method, it is considered that the fineness due to the fiber separation and the fineness due to the drawing are mixed, but according to the above-mentioned spinning conditions, the fiber is not separated but the single fiber is drawn. It turned out that it can be made fine. It is very difficult to control the fiber diameter and the fiber diameter distribution in the separation, but if the fibers are finely made with one thread, a non-woven fabric composed of fibers having high uniformity and a desired average fiber diameter is obtained. It becomes possible. Therefore, it becomes easy to achieve a highly controlled pore distribution in the separator for an aqueous electrolyte storage battery of the present invention.

(2) Measurement of basis weight (g/m ² ) According to the method specified in JIS L-1906, a test piece measuring 20 cm in length and 25 cm in width is provided at 3 locations per 1 m in the width direction of the sample and 3 locations per 1 m in the length direction. Nine places were sampled per 1 m×1 m in total, the mass was measured, and the average value was converted into the mass per unit area.

(3) Measurement of Thickness (μm) According to the method specified in JIS L-1906, the thickness at 10 points per 1 m of width was measured, and the average value was obtained.

(4) Measurement of apparent density (g/cm ³ ) Using the basis weight (g/m ² ) measured in ( ² ) above and the thickness (μm) measured in (3) above, the following formula:
Apparent density=(weight)/(thickness)
It was calculated by

(5) Measurement of porosity (%) Using the apparent density (g/cm ³ ) calculated in (4) above, the following formula:
Porosity={1-(apparent density)/(resin density)}/100
Calculated from

(6) Measurement of maximum pore diameter (Dmax), minimum pore diameter (Dmin), and average pore diameter (Dave) of nonwoven fabric A Palm Porometer (model: CFP-1200AEX) manufactured by PMI was used as a measuring device. This measurement device uses a non-woven fabric as a sample, dips the non-woven fabric in an immersion liquid with a known surface tension in advance, and applies pressure to the non-woven fabric from a state in which all pores of the non-woven fabric are covered with the immersion liquid, and the liquid film This is to measure the pore diameter of the pores calculated from the pressure at which is destroyed and the surface tension of the immersion liquid. Using PMI's Silwick as the immersion liquid, the non-woven fabric was immersed in the immersion liquid and sufficiently deaerated, and then the following formula:
d=C·r/P
{In the formula, d (unit: μm) is the pore size of the filter, r (unit: N/m) is the surface tension of the immersion liquid, and P (unit: Pa) is the liquid film of that pore size is destroyed. It is a pressure, and C is a constant determined by the wetting tension of the immersion liquid, the contact angle, and the like. } Was used to determine the pore size.

The flow rate (wetting flow rate, unit: L/min) when the pressure P applied to the filter immersed in the immersion liquid was continuously changed from low pressure to high pressure was measured. At the initial pressure, even the liquid film with the largest pores is not destroyed, so the flow rate is 0 L/min. As the pressure is increased, the liquid film with the largest pores is destroyed and a flow rate is generated (bubble point). The pore diameter (μm) obtained by substituting the pressure at the bubble point into the above formula was defined as the maximum pore diameter (Dmax). When the pressure was further increased, the flow rate increased with the pressure. The flow rate at the pressure when the liquid film of the smallest pores is broken matches the flow rate when the nonwoven fabric is in a dry state (dry flow rate). Therefore, the pore diameter (μm) obtained by substituting the value of the pressure when the dry flow rate was matched was taken as the minimum pore diameter (Dmin). In this measuring method, the value obtained by dividing the wetting flow rate at a certain pressure P by the dry flow rate at the same pressure is called the cumulative filter flow rate (unit: %). The pore size of the liquid film that is destroyed at the pressure at which the cumulative filter flow rate becomes 50% is called the average flow pore size (μm). This average flow pore diameter (μm) was defined as the average pore diameter (Dave).

(7) Measurement of coefficient of variation of formation Measurement device model: FMT-MIII manufactured by Nomura Trading Co., Ltd. was used. With the sample (nonwoven fabric) not set, the amount of transmitted light when the light source was turned on/off was measured with a CCD camera. Subsequently, the amount of transmitted light was measured in the same manner with the non-woven fabric cut into A4 size set, and the average transmittance, the average absorbance, and the standard deviation (variation of the absorbance) were obtained. The coefficient of variation of formation was calculated by standard deviation÷average absorbance×10. The formation index has a very high correlation with visual observation and directly represents the formation of the nonwoven fabric. Further, the coefficient of variation of formation becomes smaller as the formation becomes better and becomes larger as the formation becomes worse.

(8) Measurement of suction height (mm) Three points per 1 m in the width direction of the non-woven fabric, a test piece (width of about 2.5 cm x length of 20 cm) were sampled and used for the water absorption test method of JIS L-1907 textile products. The measurement was performed according to the described Bayrec method. A standard solution having a wetting index standard solution of 50 mN/m was used as the wicking solution. A mark was made at a length of 2 cm from one end of the test piece, and one end of the mark was impregnated with the standard liquid up to the mark (2 cm) and allowed to stand for 10 minutes. The test piece was pulled up from the reference liquid, the suction height (the length from the mark of the test piece to the end of the sucked liquid) was measured, and the average value was taken as the suction height (mm).

(9) Measurement of liquid retention (%) A non-woven fabric test piece (150 mm x 150 mm) was prepared and its dry mass (Wa) was measured. The test piece was spread and dipped in a KOH aqueous solution, pulled out from the aqueous solution after 1 hour, and allowed to stand in a windless room with a relative humidity of 65% for 10 minutes, and the mass (Wb) of the test piece was measured to determine the electrolyte retention rate (%). The following formula:
Electrolytic solution retention rate (%)=(Wa-Wb)/Wa×100
It was calculated by

(10) Measurement of Tensile Strength (N/15 mm) Except for 10 cm at each end of the non-woven fabric, test pieces each having a width of 15 mm and a length of 200 mm were sampled at 5 locations per 1 m in the width direction of the non-woven fabric. A load was applied until the test piece broke, and the average value of the strength of the test piece in the MD direction at the maximum load was obtained.

(11) Measurement of volume resistance (Ω·cm) Measuring device: HIOKI's Digital Super Megohmmeter and HIOKI's flat plate sample electrode SME-831 1 were used. A 100 mm×100 mm test piece (nonwoven fabric) was prepared, and the volume resistance value (Ω·cm) was measured under the measurement conditions of voltage 10 V and measurement time: 60 seconds.

[Production of electrode group]
Spiral with the separator of the above-mentioned Example and Comparative Example interposed between a paste-like nickel positive electrode (40 mm width) using a foamed nickel base material as a current collector of a battery and a paste-like hydrogen storage alloy negative electrode (40 mm) It was wound into a shape and an electrode group was prepared.

[Production of battery]
The electrode group manufactured as described above was housed in a cylindrical outer can, and an electrolytic solution (10% KOH aqueous solution) was injected. The outer can was sealed to produce a cylindrical nickel-hydrogen battery (capacity: 1.7 Ah). In order to form the obtained nickel-hydrogen battery, the battery was charged at 0.1° C. for 15 minutes at 25° C., and charging was repeated 5 times until the final voltage reached 0.8V.

(12) Measurement of defective rate (%) When manufacturing a battery, it was determined that a battery was electrically connected between electrodes due to a burr at an electrode end and a battery short-circuited due to a separator penetrating and breaking. The rate of defects per 1000 pieces was defined as the defect rate (%).

(13) Measurement of capacity retention rate (%) Using the formed nickel-hydrogen battery obtained as described above, the discharge capacity (Ca) after charging at 1 C and the storage capacity at 40° C. for 7 days The discharge capacity (Cb) was measured and the capacity retention rate (%) was calculated by the following formula:
Capacity retention rate (%)=(Cb/Ca)×100
It was calculated by

(14) Evaluation of cycle characteristics Using the nickel-metal hydride battery that has been formed and obtained as described above, the battery is charged at 0.1 C, rested for 15 minutes, and discharged at a discharge rate of 0.2 C until the final voltage reaches 0.8 V. Charging and discharging with one cycle of discharging was repeated, and the number of cycles when the initial capacity was less than 80% was measured. It indicates that the larger the number of cycles, the better the cycle characteristics. When the number of cycles was 499 times or less, it was designated as "x", 500 cycles or more was designated as "O", and 800 cycles or more was designated as "A".

Aqueous electrolyte storage battery separator of the present invention, ion permeability, electrolyte wettability and liquid retention, and, because it is excellent in electrical insulation, by using it as an aqueous electrolyte storage battery separator, high capacity and It is possible to manufacture a highly reliable aqueous electrolyte storage battery with low resistance, long cycle life, and high reliability. Therefore, the present invention can be suitably used in a wide range of fields such as in-vehicle nickel hydrogen batteries.

Claims (11)

Formulas (1) to (4) below:
Dmax≦20 μm. ． ． (1)
0.1 μm≦Dmin. ． ． (2)
Dmax/Dave<3.00. ． ． (3)
Dmax/Dmin<5.00. ． ． (4)
{In the formula, Dmax is the maximum pore diameter (μm), Dave is the average pore diameter (μm), and Dmin is the minimum pore diameter (μm). ] A lead-acid battery composed of a non-woven fabric having a pore size distribution satisfying the following conditions and having an average fiber diameter of 0.1 μm or more and 5.0 μm or less and a fiber length of 150 mm or more, and having a formation variation coefficient of 100 or less. Alternatively, a separator for an aqueous electrolyte storage battery, which is either an alkaline battery. The separator for an aqueous electrolyte storage battery according to claim 1, wherein the nonwoven fabric has an average pore diameter (Dave) of 10 μm or less. The separator for an aqueous electrolyte storage battery according to claim 1, wherein the nonwoven fabric has a minimum pore diameter (Dmin) of 5 μm or less. The separator for an aqueous electrolyte storage battery according to any one of claims 1 to 3, wherein the non-woven fabric is a non-woven fabric composed of thermoplastic resin fibers. The separator for an aqueous electrolyte storage battery according to any one of claims 1 to 4, wherein the nonwoven fabric is a hydrophilically treated nonwoven fabric. The separator for an aqueous electrolyte storage battery according to claim 1, wherein the nonwoven fabric has a thickness of 10 to 300 μm and a basis weight of 5 to 100 g/m ² . The separator for an aqueous electrolyte storage battery according to claim 1, wherein the nonwoven fabric has a porosity of 30 to 95%. A laminated non-woven fabric having at least two non-woven fabric layers in which a non-woven fabric is further laminated on the non-woven fabric , the following formulas (1) to (4):
Dmax≦20 μm. ． ． (1)
0.1 μm≦Dmin. ． ． (2)
Dmax/Dave<3.00. ． ． (3)
Dmax/Dmin<5.00. ． ． (4)
{In the formula, Dmax is the maximum pore diameter (μm), Dave is the average pore diameter (μm), and Dmin is the minimum pore diameter (μm). } The pore size distribution which satisfy|fills}, and the formation variation coefficient is comprised from 100 or less, The separator for aqueous electrolyte storage batteries of any one of Claims 1-7. The separator for an aqueous electrolyte storage battery according to any one of claims 1 to 8, wherein the nonwoven fabric is a calendered nonwoven fabric or a laminated nonwoven fabric. An aqueous electrolytic solution storage battery comprising the aqueous electrolytic solution storage battery separator according to claim 1. An alkaline secondary battery comprising the separator for an aqueous electrolyte storage battery according to claim 1.