JP2002279958A - Separator for battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a separator for a battery that can smoothly generate electromotive reaction, without shortening the life time of the battery, even when the temperature of the battery becomes high and moreover, causing no problem of short circuit or the like, when forming an electrode plate group. SOLUTION: This separator for the battery is formed of nonwoven fabric, comprising polyphenylene sulfide fiber at 30-77 mass%, fiber with the Young's modulus of 6,000 kg/mm<2> or higher at 3-30 mass%, and fused fiber at 20-50 mass%, with only the fused fiber being fused. Each of the fibers constituting the nonwoven fabric is not fibrillated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a battery separator.

[0002]

2. Description of the Related Art Conventionally, a positive electrode and a negative electrode of an alkaline battery are separated so as to prevent a short circuit and to maintain an electrolytic solution so that an electromotive reaction can be carried out smoothly. A separator is used.

As such a separator, a non-woven fabric made of polyamide fibers such as 6 nylon fibers,
Nonwoven fabrics made of polyolefin fibers such as polypropylene fibers have been developed. Such a separator could be used satisfactorily for ordinary nickel-cadmium batteries and nickel-hydrogen batteries.For example, nickel-cadmium batteries and nickel-hydrogen batteries for power tools requiring high-rate discharge characteristics are required. Since the battery temperature may reach 180 ° C. or more depending on the use conditions, the separator using 6 nylon fibers or the like having a softening temperature of about 180 ° C. is softened and deformed and decomposed, and the melting point is 160 ° C.
In some cases, a separator using polypropylene fibers of a certain degree may shorten the battery life, for example, due to melting and deformation, short-circuiting, and reduced permeability of oxygen generated from the positive electrode to the negative electrode. .

[0004] Therefore, it is considered that the above-mentioned problem can be solved by using a heat-resistant fiber which does not soften or melt at a temperature of about 180 ° C. As such heat-resistant fibers, there are polyphenylene sulfide fibers, and battery separators using the fibers have been proposed (for example, Japanese Patent Application Laid-Open Nos. Hei 7-262980 and Hei 9-92).
67786, JP-A-10-64502, etc.).

[0005] However, conventionally proposed separators are composed of 100% polyphenylene sulfide fibers, and are, for example, nonwoven fabrics in which expanded polyphenylene sulfide fibers are fixed by thermocompression bonding of undrawn polyphenylene sulfide fibers. This non-woven fabric is made of the same resin composition, despite the difference between being stretched and unstretched. Of the separator. Since this paper-like separator is not elastic and cannot be in close contact with the electrode plates, it is difficult not only to cause a smooth electromotive reaction, but also to arrange the separators between the electrode plates to form an electrode plate group. In such a case, cracks are easily formed due to burrs and edges of the electrode plate, and short-circuits are easily caused.

On the other hand, battery separators using polyphenylene sulfide fibers and fibrillated pulp-like aramid fibers have also been proposed (see, for example, Japanese Patent Application Laid-open No.
01-40597).

Since this battery separator contains pulp-like aramid fibers in addition to polyphenylene sulfide fibers, it is more elastic than one made of 100% polyphenylene sulfide fibers and can be in close contact with the electrode plate. However, since the blended fibers are pulp-like aramid fibers, the permeability of oxygen generated from the positive electrode to the negative electrode is reduced as in the case where the separator is melt-deformed, which may shorten the battery life. Was. This was remarkable in batteries requiring high-rate discharge characteristics.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems. Even when the temperature of the battery becomes high, the electromotive reaction can be smoothly generated without shortening the battery life. It is an object of the present invention to provide a battery separator which can be operated and has no problem such as a short circuit when forming an electrode plate group.

[0009]

The battery separator of the present invention (hereinafter simply referred to as "separator") has a polyphenylene sulfide fiber (hereinafter referred to as "PPS fiber") of 30 to 77 mass% and a Young's modulus of 30% to 77%. 6000k
g / mm ² or more fiber (hereinafter referred to as “high Young's modulus fiber”) 3 to 30% by mass and fused fiber 20 to 50 m
as non-woven fabric, wherein the non-woven fabric contains only the fused fibers, and the fibers constituting the non-woven fabric are not fibrillated.

[0010] The separator of the present invention is provided with heat resistance by containing PPS fibers, so that the battery life is not shortened even when the battery becomes hot. By the combination of relatively non-fused relatively soft PPS fiber and rigid high Young's modulus fiber, it is possible to form an elastic separator that is not paper-like, so that it can be in close contact with the electrode plate, A smooth electromotive reaction can be caused. In addition to being not paper-like, the high Young's modulus fiber can resist burrs and edges of the electrode plate due to its rigidity, and thus is a separator in which a short circuit is unlikely to occur when forming the electrode plate group. Furthermore, the nonwoven fabric forming the separator is made of non-fibrillated fibers and does not impede oxygen permeability, so that the battery life is also excellent in this respect.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The nonwoven fabric constituting the separator of the present invention, which contains PPS fibers, imparts heat resistance to the separator. As a result, even when the battery is heated to a high temperature of 200 ° C. or higher. It can function as a separator without deterioration.

The PPS fiber is a fiber composed of a polymer in which 90 mol% or more of the constituent units are composed of [-C ₆ H ₄ S-].

If the amount of the PPS fiber is small, the heat resistance is poor and the PPS fiber cannot be used in a battery which may be heated to a high temperature.
It must occupy 0 mass% or more, and more preferably occupies 50 mass% or more. The upper limit is set at 7 from the viewpoint of the balance with the high Young's modulus fiber and the fusion fiber described later.
It is 7 mass%, and more preferably 70 mass%.

The fineness of this PPS fiber is 0.5 dtex or more.
It is preferably 3.5 dtex, and 0.5 dtex or more.
More preferably, it is 2.2 dtex. Further, the fiber length varies depending on the form of the nonwoven fabric. When the nonwoven fabric is a wet nonwoven fabric, the length is preferably about 1 to 20 mm, more preferably 2 to 15 mm. On the other hand, when it is made of a dry nonwoven fabric, it is preferably 20 to 100 mm, more preferably 20 to 60 mm. The PPS fiber preferably has no crimp when the nonwoven fabric is a wet nonwoven fabric, and preferably has a crimp of 6 ridges / 25 mm to 24 ridges / 25 mm when the nonwoven fabric is a dry nonwoven fabric.

The nonwoven fabric constituting the separator of the present invention has a Young's modulus of 6,000 k in addition to the above-mentioned PPS fiber.
g / mm ² or higher. By including this high Young's modulus fiber, the separator is not paper-like and can be closely adhered to an elastic electrode plate, so that an electromotive reaction can be smoothly generated and has elasticity. In addition, since it is possible to resist burrs and edges of the electrode plate, it is possible to prevent a short circuit at the time of forming the electrode plate group.

The higher the Young's modulus is, the more excellent the effect is. Therefore, the Young's modulus is more preferably 7000 kg / mm ² or more. On the other hand, the upper limit is not particularly limited, but about 10,000 kg / mm ² is appropriate. The “Young's modulus” in the present invention is JIS L 101
5 means the value of apparent Young's modulus calculated from the initial tensile resistance measured by the chemical fiber staple test method.

As the high Young's modulus fiber, for example, a para-based wholly aromatic polyamide fiber or an average molecular weight of 1,000,000 to 5
Ultra-high molecular weight polyethylene fibers of about one million can be mentioned. Examples of the former para-based wholly aromatic polyamide fibers include, for example, poly-p-phenylene terephthalamide,
Poly-p-benzamide, poly-p-amide hydrazide, poly-p-phenylene terephthalamide-3,4-
Fibers composed of a resin component such as diphenyl ether terephthalamide can be mentioned.

Such a high Young's modulus fiber is 3 mass% of the whole nonwoven fabric constituting the separator so that it can be used as an elastic separator, and short-circuiting is hardly caused by burrs and edges of the electrode plate. It must be contained in the above amount, more preferably 5% by mass or more, even more preferably 10% by mass or more. On the other hand, the upper limit is 30 mass%, more preferably 20 mass%, in consideration of the above-mentioned PPS fiber and fusion fiber.

The nonwoven fabric constituting the separator of the present invention further contains a fusion fiber. The fused fibers maintain the nonwoven fabric form or impart tensile strength and rigidity to the nonwoven fabric by fusing.

This fused fiber is made of PPS so as not to soften or fuse even PPS fiber or high Young's modulus fiber.
It preferably contains a fusion component that can be fused at a temperature lower than the softening temperature of the fiber or the high Young's modulus fiber. For example, when the high Young's modulus fiber is a para-based wholly aromatic polyamide fiber, since the para-based wholly aromatic polyamide fiber has no melting point, only the PPS fiber may be considered, and the PPS fiber has a softening temperature of about 270 ° C. Therefore, it is preferable to use a fusion fiber containing a fusion component having a melting point lower than 270 ° C. When this fusion component is made of a resin having an amide bond (for example, polyamide resin such as 6 nylon and 6-6 nylon), it has excellent fusion property with para-based wholly aromatic polyamide fiber and PPS fiber. The coating component is a polyolefin resin (for example, polyethylene, polypropylene, ethylene-butene-propylene copolymer, etc.)
, It is easy to obtain the battery characteristics without being affected by the electrolytic solution.

When the high Young's modulus fiber is made of ultra-high molecular weight polyethylene fiber, the softening temperature of the ultra-high molecular weight polyethylene fiber is lower than that of the PPS fiber. Since the softening temperature of ultra-high molecular weight polyethylene is about 130 ° C., a melting component having a melting point lower than 130 ° C. (for example, low-density polyethylene, acrylic acid-ethylene copolymer, methacrylic acid-ethylene It is preferable to use a fused fiber containing a polymer or the like. Among these fused fibers, ultra high molecular weight polyethylene fibers and PP
It is preferable to use a fusion fiber containing a fusion component made of low-density polyethylene, which is excellent in fusion property with the S fiber.

Such a fused fiber may be composed of a single component. However, in order not to reduce the retention of the electrolyte and the oxygen permeability, a non-fused component other than the fused component is used. It is preferable to use a fusion fiber containing a fusion component. When the fusion fiber is composed of two or more resin components, the cross-sectional shape of the fusion fiber is, for example, a core-sheath type, a side-by-side type,
It can be sea-island type, multiple bimetal type, orange type. Among them, a core-sheath type or a sea-island type having a large fusion area is preferable.

In order to maintain the form of the non-woven fabric constituting the separator and to impart tensile strength and rigidity to the non-woven fabric, the fused fibers need to be contained in the whole non-woven fabric constituting the separator by 20 mass or more. . On the other hand, the upper limit is 50 mass% in view of the balance with the PPS fiber and the high Young's modulus fiber, and more preferably 30 mass%.

The nonwoven fabric constituting the separator of the present invention can contain fibers other than the above-mentioned PPS fibers, high Young's modulus fibers, and fusion fibers (hereinafter, referred to as “other fibers”). As this other fiber, for example,
Fibers having an ethylene-vinyl alcohol copolymer on the fiber surface and ultrafine fibers having a fiber diameter of 5 μm or less can be contained. When the former fiber is included, the hydrophilicity of the separator is improved, so that the retention of the electrolytic solution is improved. When the latter ultrafine fiber is included, a micro short circuit can be prevented or the electrolyte can be retained. Performance can be improved.

The ultrafine fibers having a fiber diameter of 5 μm or less are
For example, a fiber composed of two or more resin components can be obtained by a melt blow method or a mechanical action (for example, a fluid flow) and / or a chemical action (for example, swelling or extraction with a solvent).

The other fibers must be 47 mass% or less of the non-woven fabric fibers constituting the separator, and more preferably 20 mass% or less.

The constituent fibers (for example, PPS fiber, high Young's modulus fiber, fused fiber, etc.) of the non-woven fabric constituting the separator of the present invention are not fibrillated. The present invention can also be applied to batteries that require characteristics. In particular,
Since the high Young's modulus fiber is not fibrillated, the separator can be more elastic because it is a more elastic separator, and has the effect of being able to resist burrs and edges of the electrode plate.

The term "non-fibrillated fiber" means that the fiber is not a fiber branched into fine fibers. For example, fibers beaten by a beater or a refiner, pulp and the like are fibrillated fibers.

Although the nonwoven fabric of the present invention is composed of the above-mentioned fibers, only the fused fibers are in a fused state.
That is, since the PPS fiber and the high Young's modulus fiber are not in a fused state, they are not in the form of a paper but have a moderate elasticity due to the softness of the PPS fiber and the rigidity of the high Young's modulus fiber.

Such a state can be expressed by a thickness holding ratio, and the thickness holding ratio is preferably 85% or more and 95% or less. When the thickness retention is less than 85%, the separator is easily crushed, the electrolyte is easily released from the separator, the retention of the electrolyte is low, the liquid is easily withered, and the battery life is easily shortened. A more preferable thickness retention is 90% or more. On the other hand, when the thickness retention rate exceeds 95%, since the separator is paper-like, the followability of the separator to the electrode plate is poor, and the internal pressure of the battery increases.
Since the battery capacity is low or the high-rate charge and discharge tend to be inferior, the more preferable thickness retention rate is 93% or less.

The thickness retention is a percentage of the thickness under a load of 1000 g measured by a micrometer with respect to the thickness under a load of 500 g. That is, it means a value obtained by the following equation. (Thickness retention,%) = (T ₁₀₀₀ / T ₅₀₀ ) × 10
0 Here, T ₁₀₀₀ is ₁₀₀₀ by a micrometer.
g means the thickness when a load is applied, and T ₅₀₀ means the thickness when a 500 g load is applied by a micrometer.

The nonwoven fabric of the present invention has an areal density of 30 to 100 g.
Is preferably from / m ^2, and more preferably 40 and 80 g / m ^2. When the areal density is less than 30 g / m ² ,
If the tensile strength exceeds 100 g / m ² , the nonwoven fabric becomes too thick and it is difficult to increase the capacity of the battery. Further, the thickness is preferably 0.08 to 0.3 mm.

Since the separator of the present invention is provided with the above-mentioned nonwoven fabric, it has excellent heat resistance, elasticity and oxygen permeability, can generate an electromotive reaction smoothly, and can form an electrode plate group. Sometimes a short circuit hardly occurs.

The separator of the present invention may be composed of only the nonwoven fabric as described above, or may be provided with a porous material such as a net, a microporous film, or a mesh in addition to the nonwoven fabric.

The separator of the present invention has an oxygen and / or sulfur-containing functional group (for example, a sulfonic acid group, a sulfonic acid group) on the surface of a separator constituent material (particularly, the surface of a non-woven fabric constituent fiber) so as to have excellent electrolyte retention. , A sulfofluoride group, a carboxyl group, a carbonyl group, etc.), a hydrophilic monomer is graft-polymerized, a surfactant is attached, or a hydrophilic resin is attached. .

The separator of the present invention can be manufactured, for example, as follows.

First, a non-fibrillated PPS fiber, a high Young's modulus fiber and a fused fiber are prepared. The fiber length of these fibers varies depending on the method of forming the fiber web, and when forming the fiber web by the wet method, it is 1 to 20 m.
When using a fiber of about m length and forming a fiber web by a dry method such as a card method or an air lay method, 20 to 1
A fiber having a length of about 00 mm is used.

Next, the PPS fiber is 30 to 77 mass
%, The fiber web is blended so that the high Young's modulus fiber is 3 to 30 mass% and the fused fiber is 20 to 50 mass%. As a method of forming this fiber web,
For example, there are a wet method and a dry method (for example, a card method, an air-lay method, and the like). A nonwoven fabric may be manufactured from these single fiber webs, or the same or different fiber webs 2 may be used.
Although a nonwoven fabric may be manufactured from more than one sheet, the use of a fiber web containing fibers having a long fiber length can increase the strength of the separator, and therefore the fiber web formed by a dry method is included. preferable. When uniform dispersion of fibers is also required, it is preferable to laminate a fiber web formed by a dry method and a fiber web formed by a wet method. When two or more different types of fiber webs are laminated (for example, when a fiber web formed by a dry method and a fiber web formed by a wet method are laminated), the battery performance is substantially reduced so as not to deteriorate. It is preferable to mix the fibers sufficiently so that the fibers consist of one layer. As the mixing method, a treatment with a fluid flow can be mentioned.

Next, the fused fibers constituting the formed fiber web are fused to produce a nonwoven fabric. The fusion treatment of the fused fibers may be performed under no pressure, may be performed under pressure, or may be performed after melting under no pressure, but in order to impart elasticity to the nonwoven fabric. It is preferable to press after melting under no pressure, and more preferably, immediately after melting under no pressure.

When heating and pressurization are performed simultaneously, the heating temperature is preferably in the range from the softening temperature of the fusion component of the fusion fiber to the melting point. When the pressure is applied after melting under no pressure, the softening temperature of the adhesive component of the fusion-bonded fiber may be lower than the melting point by 20%.
It is preferred that the temperature be in the range of not less than ° C. and up to a high temperature. The pressurizing conditions include a linear pressure of 5 to 30 N / cm.
It is preferred to be on the order of magnitude.

In the present invention, the "softening temperature" refers to a temperature at which a differential scanning calorimeter is used to give a starting point of a melting endothermic curve obtained by raising the temperature from room temperature at a temperature rise rate of 10 ° C./min. It refers to the temperature at which the maximum value of the melting endothermic curve obtained by raising the temperature from room temperature at a temperature rise rate of 10 ° C./min using a differential scanning calorimeter is given.

If the nonwoven fabric constituting the separator of the present invention is entangled by a fluid flow prior to the above-mentioned fusion treatment, a nonwoven fabric having further excellent strength can be obtained.
The processing conditions by this fluid flow include, for example, a fluid flow having a pressure of 1 MPa to 30 MPa from a nozzle plate in which nozzles are arranged in one or more rows at a nozzle diameter of 0.05 to 0.3 mm and a pitch of 0.2 to 3 mm. Just squirt. Such a fluid stream is ejected at least once onto one or both sides of the fiber web. When the non-opening portion of the support for supporting the fiber web is thick when entangling by the fluid flow, the obtained nonwoven fabric has large holes, and a short circuit easily occurs. It is preferable to use a support having a thickness of 0.25 mm or less.

The thus obtained nonwoven fabric can be used as a separator as it is, or the nonwoven fabric produced as described above can be used, for example, in a net, a microporous film,
It may be integrated with a porous body such as a mesh. As the integration method, for example, a method utilizing the fusion property of the fusion fibers and / or the porous material constituting the nonwoven fabric, a method of entanglement by applying a fluid flow, or the like, alone or in combination Can be implemented. In addition, these integration methods may be performed after forming the nonwoven fabric from the fiber web, instead of after forming the nonwoven fabric.

When the electrolyte retention of the nonwoven fabric thus produced is insufficient, it is preferable to carry out a hydrophilic treatment in order to improve the electrolyte retention. In particular, when the high Young's modulus fiber is made of ultra-high molecular weight polyethylene and the fusion component of the fusion fiber is made of a polyolefin resin,
Since the retention of the electrolyte tends to be insufficient, it is preferable to perform a hydrophilic treatment.

As the hydrophilic treatment, for example, at least one hydrophilic treatment such as a sulfonation treatment, a fluorine gas treatment, a graft treatment, a surfactant treatment, a discharge treatment, and a hydrophilic resin adhesion treatment is carried out. An oxygen and / or sulfur-containing functional group (for example, a sulfonic acid group, a sulfonate group, a sulfofluoride group, a carboxyl group, a carbonyl group, etc.) is introduced into the fiber surface, a hydrophilic monomer is graft-polymerized, It is preferable to attach an activator or a hydrophilic resin. Such a hydrophilization treatment may be performed at the fiber stage (that is, at a stage before the formation of the nonwoven fabric), but the hydrophilization treatment after the formation of the nonwoven fabric is more excellent in workability. When the separator contains a material other than the nonwoven fabric, it is preferable that the material other than the nonwoven fabric is subjected to a hydrophilic treatment. The non-woven fabric and the material other than the non-woven fabric can be simultaneously subjected to the hydrophilic treatment, or can be separately subjected to the hydrophilic treatment. Hereinafter, a method of performing the hydrophilic treatment after the formation of the nonwoven fabric will be described, but in other cases, the method can be performed in exactly the same manner.

As the sulfonation treatment, for example, the above-mentioned nonwoven fabric is immersed in a solution containing fuming sulfuric acid, sulfuric acid, chlorosulfuric acid or sulfuryl chloride to introduce sulfonic acid groups, There is a method of introducing a sulfonic acid group by contacting the nonwoven fabric as described above, or a method of introducing a sulfonic acid group by causing discharge in the presence of a sulfur monoxide gas or a sulfur dioxide gas.

As the fluorine gas treatment, for example, a fluorine gas diluted with an inert gas (eg, nitrogen gas, argon gas, etc.) and at least one kind selected from oxygen gas, carbon dioxide gas, sulfur dioxide gas, etc. The nonwoven fabric can be made hydrophilic by exposing the nonwoven fabric to a mixed gas with the above gas.

Examples of the graft polymerization treatment of the vinyl monomer include a method in which the nonwoven fabric is immersed in a solution containing the vinyl monomer and a polymerization initiator and heated, a method in which the nonwoven fabric is coated with the vinyl monomer and then irradiated with radiation, and a method in which the nonwoven fabric is irradiated with radiation. A method of contacting with a vinyl monomer after irradiation with radiation,
There is a method in which a vinyl monomer solution containing a sensitizer is applied to a nonwoven fabric and then irradiated with ultraviolet rays. As the vinyl monomer, for example, acrylic acid, methacrylic acid, acrylic acid ester, methacrylic acid ester, vinylpyridine, vinylpyrrolidone or styrene can be used. In addition, when styrene is graft-polymerized, it is preferable to sulfonate so as to have an excellent affinity with an electrolytic solution. In addition, when the nonwoven fabric is modified by ultraviolet irradiation, corona discharge, plasma discharge, or the like before the vinyl monomer solution is brought into contact with the nonwoven fabric, affinity with the vinyl monomer solution is increased, so that graft polymerization can be performed efficiently.

As the treatment with a surfactant, for example, an anionic surfactant (for example, an alkali metal salt of a higher fatty acid, an alkyl sulfonate, or a sulfosuccinate), or a nonionic surfactant (for example,
The nonwoven fabric can be immersed in a solution of a polyoxyethylene alkyl ether or a polyoxyethylene alkylphenol ether, or the solution can be applied to the nonwoven fabric or sprayed on the nonwoven fabric.

Examples of the discharge treatment include a corona discharge treatment, a plasma treatment, a glow discharge treatment and an electron beam treatment. In addition, under the atmospheric pressure in the air, between the pair of electrodes each carrying a dielectric, a nonwoven fabric is arranged so as to be in contact with both of these dielectrics, an AC voltage is applied between these two electrodes, With the method of generating discharge in the internal voids of the nonwoven fabric, the surface of the fiber inside the nonwoven fabric can be hydrophilized, so that a separator having excellent internal pressure characteristics can be manufactured.

As the hydrophilic resin application treatment, for example, a hydrophilic resin such as carboxymethyl cellulose, polyvinyl alcohol, crosslinkable polyvinyl alcohol, or polyacrylic acid can be attached. After dissolving or dispersing these hydrophilic resins in a suitable solvent, the nonwoven fabric can be immersed in the solvent, or the solvent can be applied or sprayed on the nonwoven fabric and dried to adhere.

The crosslinkable polyvinyl alcohol includes, for example, polyvinyl alcohol in which a part of the hydroxyl group is substituted with a photosensitive group. More specifically, a styrylpyridinium-based photosensitive group, styrylquinolinium And polyvinyl alcohols in which some of the hydroxyl groups are substituted with styrylbenzothiazolium-based compounds.
This crosslinkable polyvinyl alcohol can also be crosslinked by irradiating light after adhering to the nonwoven fabric in the same manner as other hydrophilic resins. Such a polyvinyl alcohol in which a part of the hydroxyl group is substituted by a photosensitive group is excellent in alkali resistance and contains a large amount of a hydroxyl group capable of forming a chelate with an ion. It forms a chelate with ions before the metal is deposited, and can prevent short-circuiting between electrodes, so that it can be suitably used.

The separator of the present invention can smoothly generate an electromotive reaction without shortening the battery life even when the temperature of the battery becomes high, and does not cause a problem such as a short circuit at the time of forming the electrode plate group. Things. Therefore, the separator of the present invention, for example, alkaline manganese batteries, mercury batteries, silver oxide batteries, primary batteries such as air batteries, nickel-
Cadmium battery, silver-zinc battery, silver-cadmium battery,
It can be used for a secondary battery such as a nickel-zinc battery and a nickel-hydrogen battery, and can be particularly suitably used for a nickel-cadmium battery and a nickel-hydrogen battery requiring high-rate discharge characteristics.

Examples of the separator of the present invention will be described below, but the present invention is not limited to these examples.

[0055]

(Example 1) Poly-p-phenylene terephthalate
Luamide fiber (Young's modulus: 7320 kg / mm ², Fiber
Degree: 1.7 dtex, fiber length: 38 mm, fibrillation
Not made), the core component is made of 66 nylon,
6 minutes nylon (melting point: 215 ° C, softening temperature: 180
C) core-sheath type composite fused fiber (fineness: 1.7 dte
x, fiber length: 38 mm, not fibrillated)
PPS fiber (fineness: 2.2 dtex, fiber length: 51 m
m, number of crimps: 12 peaks / 25 mm, softening temperature: 270
° C, not fibrillated).

Next, 10 mass% of poly-p-phenylene terephthalamide fiber and core-sheath type composite fusion fiber 35
Mass% and 55 mass% of PPS fibers were blended and then carded to form a unidirectional fiber web.

Next, the unidirectional fiber web was heated at a temperature of 2 ° C.
Immediately after heating to 20 ° C., pressure was applied at a linear pressure of 9.8 N / cm to fuse only the sheath component of the core-sheath composite fused fiber.
A separator having an areal density of 65 g / m ² and a thickness of 0.13 mm was produced.

Example 2 Ultra high molecular weight polyethylene fiber (Young's modulus: 10,000 kg / mm ² , fineness: 1 dte)
x, fiber length: 38 mm, not fibrillated)
Core-sheath composite fused fibers (fineness: 1.7 dtex, fiber length: 51 mm, non-fibrillated) composed of polypropylene as the core component and low-density polyethylene as the sheath component (melting point: 115 ° C., softening temperature: 110 ° C.) ) And PPS fibers (fineness: 2.2 dtex, fiber length: 51 mm, number of crimps: 12 peaks / 25 mm, softening temperature: 270 ° C., not fibrillated).

Next, the ultra high molecular weight polyethylene fiber 10
mass%, core-sheath type composite fused fiber 50 mass%,
After mixing with 40 mass% of PPS fibers, carding was performed to form a unidirectional fiber web.

Next, the unidirectional fiber web was heated at a temperature of 1
Immediately after heating to 20 ° C., pressure was applied at a linear pressure of 9.8 N / cm to fuse only the sheath component of the core-sheath composite fused fiber.
A fused nonwoven fabric having an areal density of 65 g / m ² and a thickness of 0.13 mm was produced.

Next, the fused nonwoven fabric is placed in a container filled with a mixed gas comprising fluorine gas (3 vol%), oxygen gas (5 vol%), sulfur dioxide gas (5 vol%) and nitrogen gas (87 vol%). The separator of the present invention (surface density: 65 g / m ² , thickness: 100 g) supplied with the fused nonwoven fabric and brought into contact with the mixed gas for 120 seconds (temperature: 20 ° C.) to introduce a sulfofluoride group on the fiber surface. 0.1
3 mm 2).

(Example 3) The same core-sheath type as in Example 1 except that the fiber length was 5 mm, the same as in Example 1, except that the fiber length was 5 mm, and the poly-p-phenylene terephthalamide fiber was 10 mass%. Composite fused fiber 35 mass
%, And a wet fiber web was formed by a wet papermaking method from a slurry in which 55 mass% of PPS fibers were dispersed as in Example 1 except that the fiber length was 5 mm and there was no crimp.

Next, the wet fiber web was heated to a temperature of 220 ° C.
Immediately after heating to ℃, pressurized at a linear pressure of 9.8 N / cm to fuse only the sheath component of the core-sheath type composite fused fiber to form a separator having an areal density of 65 g / m ² and a thickness of 0.13 mm. Manufactured.

(Comparative Example 1) PPS fiber (fineness: 2.2d)
tex, fiber length: 51 mm, number of crimps: 12 peaks / 25
mm, softening temperature: 270 ° C, not fibrillated)
And unstretched PPS fiber (fineness: 2.2 dtex, fiber length: 51 mm, number of crimps: 12 peaks / 25 mm, softening temperature: 270 ° C., not fibrillated) were prepared.

Next, 60 mass% of the PPS fiber and 40 mass% of the undrawn PPS fiber were mixed and then carded to form a unidirectional fiber web.

Next, the unidirectional fiber web was heated at a temperature of 2 ° C.
Immediately after heating to 15 ° C., pressure was applied at a linear pressure of 9.8 N / cm, and the unstretched PPS fiber was pressed to have an area density of 65 g / cm 2.
A separator having m ² and a thickness of 0.13 mm was produced.

(Comparative Example 2) 66 nylon fiber (fineness: 1.7 dtex, fiber length: 38 mm, number of crimps: 12 peaks / 25 mm, softening temperature: 240 ° C, not fibrillated) instead of PPS fiber 55 mass% 55 ma
A separator having an areal density of 65 g / m ² and a thickness of 0.13 mm was produced in the same manner as in Example 1 except that ss% was used.

Comparative Example 3 Ultra-high molecular weight polyethylene fiber (Young's modulus: 10,000 kg / mm ² , fineness: 1 dte)
x, fiber length: 38 mm, not fibrillated) 10
mass%, the core component is made of polypropylene, and the sheath component is low-density polyethylene (melting point: 115 ° C., softening temperature:
110 ° C.) core-sheath composite fused fiber (fineness: 1.7)
dtex, fiber length: 51 mm, not fibrillated) 90% by mass was mixed to form a unidirectional fiber web, except that a unidirectional fiber web was formed. A separator (area density: 65 g / m ² , thickness: 0.13 mm ² ) was produced by fusing only the sheath component of the composite fused fiber and introducing a sulfofluoride group with a mixed gas.

Comparative Example 4 The same poly-p-phenylene terephthalamide fiber as in Example 1 was used at 80 mass%, and the same 66 nylon / 6 nylon core-sheath composite fusible fiber as at Example 1 was used at 5 mass%. 1 PPS fiber same as 1
A separator having an areal density of 65 g / m ² and a thickness of 0.13 mm was produced in exactly the same manner as in Example 1 except that 5 mass% was used.

Comparative Example 5 The same poly-p-phenylene terephthalamide fiber as in Example 1 was used at 20 mass%, and the same 66 nylon / 6 nylon core-sheath composite fusible fiber as at Example 1 was used at 10 mass%. A separator having an areal density of 65 g / m ² and a thickness of 0.13 mm was produced in exactly the same manner as in Example 1, except that the same PPS fiber as in Example 1 was used at 70 mass%.

(Comparative Example 6) Pulp prepared by fibrillating poly-p-phenylene terephthalamide fiber (JIS P
8121 "Freeness measured according to the Canadian standard form measurement method of pulp freeness test method": 210 ml), 66 core nylon component, 6 nylon sheath component (melting point: 2)
Core-sheath composite fused fibers (15 ° C., softening temperature: 180 ° C.) (fineness: 1.7 dtex, fiber length: 5 mm, not fibrillated) and PPS fibers (fineness: 2.2 dt)
ex, fiber length: 5 mm, softening temperature: 270 ° C., not fibrillated).

Then, 10 mass% of poly-p-phenylene terephthalamide pulp was mixed with the core-sheath composite fused fiber 3
A wet fiber web was formed from a slurry in which 5 mass% and PPS fibers 55 mass% were dispersed by a wet papermaking method.

Next, the wet fiber web was heated to a temperature of 220 ° C.
Immediately after heating to ℃, pressurized at a linear pressure of 9.8 N / cm to fuse only the sheath component of the core-sheath type composite fused fiber to form a separator having an areal density of 65 g / m ² and a thickness of 0.13 mm. Manufactured.

(Measurement of Thickness Retention) The thickness retention of each separator was measured by the method described above. The results were as shown in Table 1.

[0075]

[Table 1] # 2: Ratio based on penetration force of Comparative Example 2 # 3: Ratio based on internal pressure of Comparative Example 1

(Measurement of High-Temperature Life Characteristics) As a current collector of an electrode, a paste-type nickel positive electrode (33 mm wide, 182 mm long) using a foamed nickel base material and a paste-type hydrogen storage alloy negative electrode (mesh metal alloy, 33 mm 247m in width
m length).

Next, each separator was 33 mm wide and 41 mm wide.
After cutting to a length of 0 mm, each was sandwiched between a positive electrode and a negative electrode and spirally wound to form an SC (sub-C) type electrode group. This electrode group was housed in an outer can, and 5N potassium hydroxide and 1N lithium hydroxide were injected into the outer can as an electrolytic solution, sealed, and the capacity was 2,000 m.
An Ah cylindrical nickel-hydrogen battery was prepared.

Next, for each cylindrical nickel-metal hydride battery, (1) charging at 120% at 0.2 C;
(2) A charge / discharge cycle consisting of discharging to a final voltage of 1 V at 10 C was repeated at a temperature of 80 ° C., and the number of cycles until the capacity reached 50% of the initial capacity was defined as the life.

The results are as shown in Table 1. As is clear from Table 1, the thickness retention of the present invention is 90 to 90%.
The battery using the 93% separator had a long battery life even at high temperatures.

(Edge Type Penetration Resistance) The separators are overlapped with each other to have a thickness of about 2 mm in total, and a handy compression tester (manufactured by Kato Tech Co., Ltd., K
ES-G5) with a stainless steel jig (thickness: 0.5 mm, tip edge angle: 60 °) at 0.0
The piercing was performed vertically at a speed of 1 cm / s, and the force required to cut the uppermost separator (penetrating force) was measured. Table 1 shows the ratio of the penetration force required to cut each separator when the penetration force required to cut the separator of Comparative Example 2 was taken as a reference (100) as the penetration resistance index (%) of the separator. It was shown to. From these results, it was predicted that the separator of the present invention was not likely to cause a short circuit because the burr of the electrode plate penetrated the separator or the separator was not easily torn by the edge of the electrode plate when manufacturing the battery. .

(Battery Internal Pressure Test) A cylindrical nickel-hydrogen battery formed in the same manner as that used in the above (measurement of high-temperature life characteristics) was charged at 20 ° C. at 0.5 ° C.
The battery internal pressure at 50% was measured. Table 1 shows the ratio when the internal pressure of the battery using the separator of Comparative Example 1 was set as a reference (100). From these results, it was found that the separator of the present invention had excellent air permeability, and thus the internal pressure of the battery was low.

(Measurement of tensile strength in longitudinal direction) Each separator cut to a width of 50 mm was placed in a tensile strength tester (Tensilon UTM-III-1 manufactured by Orientec).
00) between chucks (distance between chucks: 100 mm)
, And under the condition of a tensile speed of 300 mm / min,
The tensile strength in the longitudinal direction of each separator was measured. The results were as shown in Table 1. As described above, since the separator of the present invention has excellent tensile strength, it has been found that the battery can be efficiently manufactured without being broken even by the tension at the time of manufacturing the battery.

[0083]

The battery separator of the present invention is provided with heat resistance by containing PPS fibers, so that the battery life is not shortened even when the battery becomes hot. By the combination of relatively non-fused relatively soft PPS fiber and rigid high Young's modulus fiber, it is possible to form an elastic separator that is not paper-like, so that it can be in close contact with the electrode plate, A smooth electromotive reaction can be caused. In addition to being not paper-like, high Young's modulus fibers are
It is a separator that can resist burrs and edges of the electrode plate and is therefore less likely to cause a short circuit. Furthermore, the nonwoven fabric constituting the separator is made of non-fibrillated fibers,
Since the oxygen permeability is not impaired, the battery life is also excellent in this respect.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) D21H 13/26 D21H 13/26 27/12 27/12

Claims (4)

[Claims] 1. A polyphenylene sulfide fiber of 30
~ 77 mass% and Young's modulus is 6000 kg / mm ²
3 to 30% by mass of the above fibers and 20 to 30% of the fused fibers
A battery separator comprising: a nonwoven fabric containing 50 mass%, wherein only the fusion fibers are fused, and none of fibers constituting the nonwoven fabric is fibrillated. 2. The battery separator according to claim 1, wherein the thickness retention is 85% or more and 95% or less. 3. The battery separator according to claim 1, wherein the fibers having a Young's modulus of 6000 kg / mm ² or more are para-based wholly aromatic polyamide fibers. 4. The battery separator according to claim 1, wherein the fibers having a Young's modulus of 6000 kg / mm ² or more are ultrahigh molecular weight polyethylene fibers.