JP2003142065A - Separator for electrochemical element and method for producing the same - Google Patents

Abstract

(57) [Problem] To provide a separator for an electrochemical element which realizes an electrochemical element having a low resistance, a small leakage current and an excellent life characteristic. The melting point or the thermal decomposition temperature is 250 ° C. or more,
What is claimed is: 1. A separator for an electrochemical element comprising a nonwoven fabric containing a polymer at least partially fibrillated to a fiber diameter of 1 μm or less, wherein the total amount of cationic impurities (Na, K, Mg, Ca) contained in said nonwoven fabric is A separator for an electrochemical element having a concentration of less than 1000 ppm. The contents of Na, K, Mg, and Ca are each 10 pp.
m, 5 ppm or less, 5 ppm or less, 5 ppm or less, a raw material is dispersed in pure water having a concentration of 10 ppm or less, and the pure water is used for water production to produce a separator for an electrochemical element. .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrochemical device separator capable of realizing an electrochemical device having a low resistance, a small leakage current and excellent life characteristics, and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, the development of an environment-friendly electrochemical device has become indispensable, and prolonging the life of the electrochemical device has become an issue. For that purpose, it is necessary to improve not only the electrode material, the current collector, and the electrolytic solution, but also the separator for the electrochemical element.

One of the factors that shorten the life of the electrochemical device
One of them is a cation type impurity (Na, K, Mg, Ca) contained in the separator for electrochemical device.
For example, in a non-aqueous electrolyte battery in which carbon is used as an electrode active material and Li salt is used as an electrolyte, these cation-type impurities enter into the carbon and disturb the layer structure of the carbon to lower the capacity or reduce the internal resistance. The rise of
The life characteristics deteriorate. In an electric double layer capacitor that uses activated carbon as an electrode active material, the decomposition products of the electrolytic solution that have been partially decomposed during use due to voltage conditions, etc. are further reduced on the activated carbon by the catalytic action of these cation-type impurities, and become gas. Occurs. This gas fills the pores of the activated carbon, resulting in a decrease in capacity and an increase in internal resistance, which deteriorates life characteristics. Also, due to the generation of gas, the internal pressure may increase with time, and the safety valve may operate. In an electrolytic capacitor using a metal foil as an electrode, the metal foil is corroded by these cation-type impurities, causing an increase in leakage current and a decrease in capacity, which deteriorates life characteristics.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above problems found in the prior art. That is, an object of the present invention is to provide a separator for an electrochemical device, which realizes an electrochemical device having a low resistance, a small leakage current and an excellent life characteristic.

[0005]

In order to solve the above problems, the inventors of the present invention have conducted extensive studies on the content of cation-type impurities, and as a result, have found that electrochemical resistance is low, leakage current is small, and life characteristics are excellent. The inventors have invented a separator for an electrochemical device that realizes the device.

That is, the present invention relates to a separator for an electrochemical element, which comprises a nonwoven fabric having a melting point or a thermal decomposition temperature of 250 ° C. or higher and at least a part of which has a polymer fibrillated to a fiber diameter of 1 μm or less, The separator for an electrochemical element is characterized in that the total amount of cationic impurities (Na, K, Mg, Ca) contained in the nonwoven fabric is less than 1000 ppm.

In the present invention, the Ca content is 400 p
It is preferably less than pm and the K content is less than 100 ppm.

Na content of less than 400 ppm and M
It is preferable that the g content is less than 100 ppm.

The present invention has a melting point or thermal decomposition temperature of 250.
At least a part of the polymer contains fibrillated polymer having a fiber diameter of 1 μm or less at a temperature of ℃ or more, and a cationic impurity (N
a, K, Mg, Ca) is a method for producing a separator for an electrochemical element, which comprises a nonwoven fabric having a total content of less than 1000 ppm, wherein the content of Na, K, Mg, Ca is 10 ppm or less and 5 ppm or less, respectively. 5ppm or less, 1
In the production method, the raw material is dispersed in pure water of 0 ppm or less and the pure water is used for water-making to produce by a wet papermaking method.

The present invention has a melting point or thermal decomposition temperature of 250.
At least a part of the polymer contains fibrillated polymer having a fiber diameter of 1 μm or less at a temperature of ℃ or more, and a cationic impurity (N
a, K, Mg, Ca) is a method for producing a separator for an electrochemical element, which comprises a non-woven fabric having a total content of less than 1000 ppm, characterized in that the non-woven fabric is produced by a pure water stream treatment. It is a method for manufacturing a device separator.

In the present invention, the electrochemical device is preferably a non-aqueous electrolyte battery.

In the present invention, the electrochemical device is preferably an electric double layer capacitor.

In the present invention, the electrochemical device is preferably an electrolytic capacitor.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The separator for an electrochemical device of the present invention will be described in detail below.

The electrochemical device in the present invention means a manganese dry battery, an alkali manganese battery, a silver oxide battery, a lithium battery, a lead storage battery, a nickel-cadmium storage battery, a nickel-hydrogen storage battery, a nickel-zinc storage battery, a silver oxide-zinc storage battery, Lithium ion batteries, lithium polymer batteries, various gel electrolyte batteries, zinc-air storage batteries, iron-air storage batteries, aluminum-air storage batteries, fuel cells, solar cells, sodium sulfur batteries, polyacene batteries, electrolytic capacitors, electric double layer capacitors, etc. Refers to. The electrodes of the electrolytic capacitor and the electric double layer capacitor may be a combination of a pair of polarizable electrodes, one polarizable electrode and the other nonpolarizable electrode.

The electrolytic solution used in these electrochemical devices may be either an aqueous solution type or an organic solvent type electrolytic solution.
Examples of the organic solvent-based electrolytic solution include dimethyl carbonate, diethyl carbonate, ethylene carbonate,
Propylene carbonate, acetonitrile, propionitrile, γ-butyrolactone, α-methyl-γ-butyrolactone, β-methyl-γ-butyrolactone, γ-valerolactone, 3-methyl-γ-valerolactone, dimethyl sulfoxide, diethyl sulfoxide, dimethyl. Formamide, diethylformamide, tetrahydrofuran, dimethoxyethane, dimethylsulfolane, sulfolane, ethylene glycol, propylene glycol, methylcellosolve dissolved in an ion-dissociable salt in an organic solvent, ionic liquid (solid molten salt), etc. However, the present invention is not limited to these.

The melting point or the thermal decomposition temperature in the present invention is 2
As the polymer at 50 ° C. or higher, nylon 66, wholly aromatic polyamide, wholly aromatic polyester, wholly aromatic polyesteramide, wholly aromatic polyether, wholly aromatic polyazomedine, polyphenylene sulfide (PPS), poly-
p-phenylene benzobis thiazole (PBZT), poly-p-phenylene benzobisoxazole (PB
O), polybenzimidazole (PBI), polyetheretherketone (PEEK), polyamide-imide (P
AI), polyimide, polytetrafluoroethylene (P
TFE) and the like, and these may be used alone or in combination of two or more kinds. PBZT is a transformer type,
Any of cis type may be used. Further, among aromatic polyamides and aromatic polyesters which are not wholly aromatic, there are those whose melting point or thermal decomposition temperature is 250 ° C. or higher depending on the kind and ratio of the monomers, and these can be used. Among these, wholly aromatic polyamides, which are likely to be fibrillated due to liquid crystallinity, are particularly preferable to be para-type wholly aromatic polyamides and wholly aromatic polyesters. Wholly aromatic polyester is
It is also preferable because it has a feature that the moisture absorption rate is extremely low.

The para-type wholly aromatic polyamide is poly-p-
Examples thereof include, but are not limited to, phenylene terephthalamide, poly-p-benzamide, poly-p-amide hydrazide, poly-p-phenylene terephthalamide-3,4-diphenyl ether terephthalamide, and the like.

The wholly aromatic polyester is synthesized by combining monomers such as aromatic diol, aromatic dicarboxylic acid and aromatic hydroxycarboxylic acid and changing the composition ratio. Examples thereof include a copolymer of p-hydroxybenzoic acid and 2-hydroxy-6-naphthoic acid, but the copolymer is not limited thereto.

The melting point or the thermal decomposition temperature in the present invention is 2
At least a part of the polymer having a temperature of 50 ° C. or higher is fibrillated. The fibril in the present invention refers to a fiber mainly having a very finely divided portion in a direction parallel to the fiber axis, and at least a portion of which has a fiber diameter of 1 μm or less. In the present invention, the aspect ratio of length and width is distributed in the range of 20: 1 to 100000: 1,
Canadian standard freeness is in the range of 0 ml to 500 ml. The weight average fiber length of the fibrils is preferably 2 mm or less.

Examples of the method for producing polymer fibrils include a method of treating polymer fibers with a high-pressure homogenizer or a refiner, and a method of hydroentangling a nonwoven fabric.

Here, the high-pressure homogenizer means at least 10 kg / cm ² or more, preferably 200
~ 1000 kg / cm ² , more preferably 400-1
It is an apparatus capable of fibrillating an object with a shearing force generated by applying a pressure of 000 kg / cm ² and passing through an orifice, and then rapidly depressurizing and decelerating. In the case of a polymer, this shearing force tears mainly in the direction parallel to the fiber axis and is given as a loosening force, and gradually fibrillates. Specifically, polymer fibers or pellets with a length of 5 mm or less, preferably 3 mm
The material cut below or made into a pulp beforehand is used as a raw material, and this is dispersed in water to obtain a suspension. The concentration of the suspension is up to 25% by mass, preferably 1 to 1
It is 0%, and more preferably 1 to 2%. The suspension is introduced into a high pressure homogenizer and at least 10
kg / cm ² , preferably 200 to 1000 kg / c
A pressure of m ² , more preferably 400 to 1000 kg / cm ² , is applied, and this operation is repeated several times to several tens of times and passed through the high pressure homogenizer. In some cases, a chemical such as a surfactant may be added for treatment.

In the case of the water entanglement treatment, the nozzle diameter for injecting the water flow is preferably in the range of 10 to 500 μm.
The nozzle pitch is preferably 10 to 1500 μm. The nozzle plate needs to have a range that covers the width of the slurry being conveyed in the direction orthogonal to the conveying direction. In the transport direction, considering the fiber type, basis weight, papermaking speed, and water pressure,
The number of nozzle heads can be changed and used. The nozzle arrangement in one nozzle plate may be one row,
Multiple rows of two or more rows may be used. In the case of multiple rows, holes in adjacent rows are arranged alternately, so-called zigzag pattern,
The holes in the adjacent rows may be arranged in the same position or may be irregular. In the hydroentangling treatment of the present invention, 10 mmH ₂ O to 1
It is preferable to squeeze water in the range of 000 mmH ₂ O. The pressure of the water flow is 10 kg / cm ^{2 to} 200 kg / c
A range of m ² is preferred.

In the polymer used in the present invention, which has a melting point or thermal decomposition temperature of 250 ° C. or higher and at least a part of which is fibrillated to a fiber diameter of 1 μm or less, generation of pinholes is suppressed and leakage current is reduced. effective. The content of the polymer in the electrochemical device separator of the present invention is preferably 3% or more and 80% or less, and 10% or more, 7% or less.
0% or less is more preferable. When the content is less than 3%, pinholes are likely to be formed, and when it is more than 80%, the strength of the electrochemical device separator is likely to be insufficient.

The non-woven fabric containing the polymer used in the present invention is manufactured by forming the polymer into a sheet at the same time as forming the fiber, or forming the sheet into a sheet after forming the fiber. The nonwoven fabric used in the present invention has a melting point or thermal decomposition temperature of 250 ° C.
As described above, an organic material other than a polymer in which at least a part thereof is fibrillated may be contained. Examples thereof include polyamide such as nylon 6, polyester, polyacryl, polyether sulfone (PES), polyvinylidene fluoride and the like. These organic materials are preferably fibrous and may be fibrillated. Fiber is
Any of a single fiber, a composite fiber, and a splittable composite fiber may be used. Fineness is preferably as fine as 3.3 dtex or less, and 1 dte
x or less is more preferable.

The electrochemical device separator of the present invention comprises:
It may contain heat-fusible fibers. As the heat-fusible fiber, fibers having polyester, acrylic, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, ethylene-vinyl acetate alcohol copolymer, low melting point polyester (modified polyester), etc. Can be mentioned. As the structure of the heat-fusible fiber, in addition to the single fiber composed only of the heat-fusible component, side-by-side type, core-sheath type, parallel multi-layer type, sea-island type, multi-core type, radiating type, hollow radiating type, mosaic type , Nebula type, multi-core type, multi-core sea-island type, etc., in which both the heat-sealing component and the non-fusing component are arranged are also preferable. The core-sheath type and the multi-core sea-island type are preferable because the adhesive strength between the fibers is likely to be strong without impairing the uniformity of the separator. The fineness of the heat-fusible fiber is preferably 3.3 dtex or less. When the fineness is thicker than 3.3 dtex, uneven thickness and uneven texture of the separator for electrochemical device are likely to occur. The length of the heat-fusible fiber is preferably 15 mm or less, 5 mm
The following is more preferable. If it is longer than 15 mm, it may be entangled and become lumpy, which may cause uneven thickness or uneven texture of the separator for electrochemical element.

When the heat-fusible fiber is heat-fused, the mechanical strength such as tensile strength, puncture strength and tear strength of the separator for electrochemical device is increased. When the separator for an electrochemical device of the present invention contains the heat-fusible fiber, the content is preferably 3% or more, and is preferably as large as possible so that pinholes cannot be formed.

The electrochemical device separator of the present invention comprises:
It may contain fibrillated cellulose or bacterial cellulose. The fibrillated cellulose in the present invention, various pulp including linter, lint, solvent-spun cellulose and the like as a raw material, for example, high-pressure homogenizer, refiner, beater, those fibrillated using a grinding device, At least a part thereof has a fiber diameter of 1 μm or less and an average fiber length of 2 mm or less, preferably 1 mm or less. The fibrillated cellulose is excellent in improving the tensile strength and puncture strength of the separator for electrochemical device even in a small amount.

The separator for electrochemical device of the present invention is
Bacterial cellulose refers to bacterial cellulose produced by microorganisms. This bacterial cellulose contains cellulose and a heteropolysaccharide having cellulose as a main chain, and β-1,3 β-1,2 and other glucans. In the case of a heteropolysaccharide, the constituent components other than cellulose are hexoses such as mannose, fructose, galactose, xylose, arabinose, rhamnose, and glucuronic acid, pentacarbons, and organic acids. These polysaccharides may be composed of a single substance, but may be composed of two or more kinds of polysaccharides bonded by a hydrogen bond or the like, and any of them can be used.

The bacterial cellulose-producing microorganisms of the present invention include Acetobacter aceti subsp. Xylinum (Acetobacter a).
ceti subsp. xylinum) ATCC 1
0821, the same Pastorian (A. pasteuria
n), A. lanceens, Sarcina ventriculu
i), Bacterium xyloides
m xyloides), a bacterium belonging to the genus Judomonas, a bacterium belonging to the genus Agrobacterium, and the like, which produce bacterial cellulose can be used, but the present invention is not limited thereto.

Bacterial cellulose has a much higher binding ability between fibers than other celluloses, so that a separator for an electrochemical element having high tensile strength and puncture strength can be obtained by mixing a small amount thereof.

The electrochemical device separator of the present invention comprises:
The total amount of cationic impurities is less than 1000 ppm. The cation-type impurities in the present invention refer to Na, K, Mg, and Ca, and the content of each cation-type impurity is obtained by ashing 2 g of the separator for an electrochemical device and heating and dissolving with 0.1 N nitric acid. Is a value obtained by ionizing and quantitatively analyzing with an ion chromatograph.
If the total amount of these cation-type impurities is 1000 ppm or more, depending on the type of electrochemical device, gas may be generated due to a catalytic reaction, or the electrode foil may be corroded to increase the leakage current, resulting in a decrease in capacity or voltage. It causes deterioration and shortens the service life. If the total amount is less than 1000 ppm, these phenomena are suppressed, and the life of the electrochemical device is unlikely to be shortened.

In the present invention, when the Ca content is less than 400 ppm and the K content is less than 100 ppm, a separator for an electrochemical device having better characteristics can be obtained.

In the present invention, when the content of Na is less than 400 ppm and the content of Mg is less than 100 ppm, a separator for electrochemical device having better characteristics can be obtained.

The method for producing a separator for an electrochemical device of the present invention has a Na, K, Mg, and Ca contents of 1 each.
0ppm or less, 5ppm or less, 5ppm or less, 10pp
It is characterized in that the raw material is dispersed in pure water of m or less, and the pure water is used for water-making to produce by a wet papermaking method. By preparing a raw material using such pure water and performing wet papermaking, a separator for an electrochemical device having a small amount of cationic impurities can be obtained. Pure water having Na, K, Mg, and Ca contents of 10 ppm or less, 5 ppm or less, 5 ppm or less, and 10 ppm or less, respectively, can be obtained by treating water with an ion exchange resin. When water having a cation content exceeding this value is used, these cation-type impurities are concentrated in the separator for electrochemical elements, resulting in a separator for electrochemical elements having a large amount of cation-type impurities.

In the present invention, pure water having a cation content adjusted as described above has a solid content concentration of 0.01% to 5%.
After disintegrating and dispersing the raw material so that the amount becomes 100%, the pure water is further added to dilute it to about 0.001% to 0.1%. Wet papermaking is performed by using a paper machine, an inclined type paper machine, a combination machine composed of a combination thereof, or the like to make one layer or two or more layers. When a raw material is prepared by adding a chemical such as a dispersion aid or an antifoaming agent, it is preferable to use a nonionic (nonionic) chemical in order to prevent the incorporation of cationic impurities. You may add a suitable amount of a thickener as needed.

Synthetic fibers are catalysts for polymer synthesis,
Na, K, Mg, etc. can be used for dope and oil used during spinning.
Since a salt or solution containing Ca is used, these cation-type impurities are mixed and adhered inside or on the fiber surface.
By disintegrating and dispersing such fibers in the pure water described above and performing wet papermaking with the pure water, it is possible to prevent mixing of cationic impurities from water and to adhere to the fiber surface. Since the cationic impurities can be removed, a separator for an electrochemical element containing less of these cationic impurities can be obtained.

The method for producing a separator for an electrochemical device of the present invention is also characterized in that the non-woven fabric is treated with pure water. Pure water in this case has a conductivity of 30 μS / cm.
Use the following: There is no limitation on the temperature of pure water, but a higher temperature is preferable because the effect of cleaning cationic impurities is large. Examples of the pure water flow treatment include a method of flowing pure water from a nozzle plate and a method of ejecting pure water from the nozzle plate at a certain pressure. The number of nozzle plates is not limited to one, and it is preferable to use a plurality of nozzle plates.
The pressure for spraying pure water is preferably less than 10 kg / cm ² when the fibers of the non-woven fabric are not entangled, and preferably 10 kg / cm ² or more when entangled, which is required for the separator for electrochemical element. The condition may be selected according to the characteristics, but it is preferably less than 10 kg / cm ^{2 from the} viewpoint of preventing the formation of pinholes. The form such as the hole diameter and pitch of the nozzle plate is not particularly limited as long as the entire nonwoven fabric is hit by the water flow. A mesh wire is preferably used as the support for carrying the non-woven fabric, and the material thereof may be metal such as stainless steel or bronze, or one made of various resins. The mesh is preferably 20 mesh or more fine, and more preferably 80 mesh or more.

In the case of pure water stream treatment, 10 mmH ₂ O
It is preferable to squeeze water in the range of 1000 mmH ₂ O.
By squeezing water, water is efficiently removed from the nonwoven fabric, so that it is possible to suppress the residual cationic impurities. The pure water stream treatment may be performed on only one side of the nonwoven fabric, but it is preferable that both sides are treated. By performing the pure water stream treatment, the cationic impurities existing on the surface of the nonwoven fabric and the interstices of the fibers are washed away, so that a separator for an electrochemical element having less cationic impurities can be obtained.

The basis weight of the electrochemical device for separator of the present invention is not particularly limited but is preferably 5 to 50 g / m ^2, is used more preferably 10 to 30 g / m ^2.

The thickness of the separator for an electrochemical element in the present invention is not particularly limited, but it is preferable that it is thin from the viewpoint that the electrochemical element can be downsized and the electrode area that can be accommodated can be increased to increase the capacity. Specifically, the thickness is 10 to 300 μm, preferably 20 to 100 μm, which has strength enough not to break during assembly of the electrochemical device, has no pinholes, and has high uniformity. If it is less than 10 μm, the short-circuit failure rate at the time of manufacturing the electrochemical element increases, which is not preferable. On the other hand, 300
If the thickness is more than μm, the area of the electrode that can be accommodated in the electrochemical device decreases, and the electrochemical device has a low capacity. The separator for electrochemical device of the present invention may be used as one sheet, or as a laminate of two or more sheets.
From the viewpoint of suppressing pinholes, it is preferable to use two or more sheets in a stack.

The electrochemical device separator of the present invention comprises:
Heat treatment, calender treatment, hot pressure treatment, etc. are carried out according to the purpose of adjusting the thickness, improving strength, removing impurities, and imparting dimensional stability to body heat.

[0043]

The present invention will be described in detail below with reference to examples, but the contents of the present invention are not limited to the examples.

<Preparation of fibrillated polymer 1> Para-type wholly aromatic polyamide fiber (fineness: 2.5 dtex, fiber length: 3)
(mm) was dispersed in water to an initial concentration of 5%, and a double disc refiner was used to repeatedly beat 15 times while narrowing the clearance each time the number of times was repeated, and then 500 kg / cm ² of a high pressure homogenizer was used. Repeated 30 times under the conditions, average fiber length 0.45mm
Then, a fibrillated para-type wholly aromatic polyamide in which at least a part thereof was fibrillated to have a fiber diameter of 1 μm or less was produced. Hereinafter, this is referred to as fibrillated polymer 1.

<Preparation of fibrillated polymer 2> A pellet of wholly aromatic polyester (length: 2 mm, width: 1 mm) was dispersed in water to an initial concentration of 5%, and the number of clearances was adjusted by using a double disc refiner. After repeatedly beating 15 times while narrowing each time, the fibrillated wholly aromatic polyester having an average fiber length of 0.32 mm was prepared by repeating 15 times using a high-pressure homogenizer under the condition of 500 kg / cm ² . Hereinafter, this is referred to as fibrillated polymer 2.

<Preparation of fibrillated cellulose 1> Linters were dispersed in water to an initial concentration of 5%, beaten repeatedly 10 times using a double disc refiner, and then 500 kg / cm using a high pressure homogenizer.
Repeated 20 times under condition ² and average fiber length 0.4m
A fibrillated cellulose 1 in which at least a part of the fibers had a fiber diameter of 1 μm or less was produced.

<Pure water 1> The contents of Na, K, Mg and Ca are 0.4 ppm, 0.06 ppm and 0.1 p, respectively.
Ion-exchanged water of pm, 0.3 ppm was used as pure water 1.

<Pure water 2> The contents of Na, K, Mg and Ca are 2.6 ppm, 0.5 ppm and 0.7 pp, respectively.
Ion-exchanged water of m, 1.6 ppm was used as pure water 2.

<Pure water 3> The contents of Na, K, Mg and Ca are 8.7 ppm, 1.6 ppm and 2.2 pp, respectively.
Ion-exchanged water of m, 5.4 ppm was used as pure water 3.

<Water 1> The contents of Na, K, Mg and Ca are 16.4 ppm, 3.3 ppm and 4.5 p, respectively.
pm, 11.4 ppm water was used as water 1.

Example 1 A 16-division composite fiber comprising 55% fibrillated polymer 1 and nylon 66 and polyester alternately arranged (fineness before division 3.3 dtex, fiber length 3 mm, cross-section flatness after division). 1.1) 25%, core-sheath composite fiber comprising polyester having a melting point of 255 ° C. in the core and modified polyester having a melting point of 110 ° C. in the sheath (fineness 1.7 dtex, fiber length 5 m
m) A compounding ratio of 20% was used to disperse in pure water 1 together with a nonionic dispersion aid using a pulper, and then pure water 1 was added to dilute to a predetermined concentration and wet using a cylinder paper machine. Papermaking was performed to prepare a wet non-woven fabric having a basis weight of 18 g / m ² and a thickness of 45 μm. Both sides of the non-woven fabric were brought into contact with a drum roll heated to 200 ° C. without pressurizing and heat-treated to obtain a separator 1 for an electrochemical element.

Example 2 Wet papermaking was performed in the same manner as in Example 1 except that pure water 2 was used instead of pure water 1, and the basis weight was 18 g / m ² and the thickness was 45 μm.
Wet non-woven fabric was prepared. Both sides of the non-woven fabric were treated in Example 1
Heat treatment is performed in the same manner as for, and the separator for electrochemical device 2
And

Example 3 Wet papermaking was performed in the same manner as in Example 1 except that pure water 3 was used instead of pure water 1, and the basis weight was 18 g / m ² and the thickness was 45 μm.
Wet non-woven fabric was prepared. Both sides of the non-woven fabric were treated in Example 1
Heat treatment is performed in the same manner as for, and the separator for electrochemical device 3
And

Example 4 55% of fibrillated polymer 1 and fineness of 0.08 dte
x, fiber length 3 mm, polyamide fineness 20%, core-sheath composite fiber having the same composition as in Example 1 (fineness 1.1 dtex, fiber length 3
mm) 20%, fibrillated cellulose 1 at a compounding ratio of 5% and dispersed in pure water 1 together with a nonionic dispersion aid using a pulper, and then pure water 1 is added to dilute it to a predetermined concentration. Wet papermaking using an inclined paper machine, basis weight 18 g /
A wet nonwoven fabric with m ² and a thickness of 45 μm was produced. Both sides of the non-woven fabric are contacted with a drum roll heated to 190 ° C. without pressurizing and heat-treated to obtain a separator 4 for electrochemical element.
And

Example 5 Wet papermaking was performed in the same manner as in Example 4 except that pure water 3 was used instead of pure water 1, and the basis weight was 18 g / m ² and the thickness was 45 μm.
Wet non-woven fabric was prepared. Both sides of the non-woven fabric were tested in Example 4
Heat treatment is performed in the same manner as in, and the separator 5 for electrochemical device is used.
And

Example 6 55% fibrillated polymer 2, fineness 0.1 dtex,
After dispersing in pure water 1 with a nonionic dispersion aid using a pulper in a compounding ratio of 25% polyester fiber having a fiber length of 3 mm and 20% core-sheath composite fiber used in Example 1,
Pure water 1 was added and diluted to a predetermined concentration, and wet papermaking was performed using a short-net paper machine to prepare a wet nonwoven fabric having a basis weight of 18 g / m ² and a thickness of 45 μm. Both surfaces of the non-woven fabric were brought into contact with a drum roll heated to 210 ° C. without pressurizing and heat-treated to obtain a separator 6 for electrochemical element.

Example 7 55% fibrillated polymer 2, fineness 0.1 dtex,
After the acrylic fiber having a fiber length of 3 mm, 20%, the core-sheath composite fiber used in Example 1, 20%, and the bacterial cellulose 5% were mixed in pure water 3 together with the nonionic dispersion aid using a pulper. , Additional pure water 3 to dilute to a specified concentration, wet papermaking using a short-net paper machine, basis weight 18 g / m
^2. A wet non-woven fabric having a thickness of 45 μm was produced. Both surfaces of the non-woven fabric were heat treated in the same manner as in Example 6 to obtain a separator 7 for electrochemical element.

Example 8 25% of fibrillated polymer 1, fibrillated polymer 2
Of 25%, fineness of 0.1 dtex, 25% of polyamide fiber having a fiber length of 3 mm, and the core-sheath composite fiber 17 used in Example 1.
%, Fibrillated cellulose 1 at a compounding ratio of 8% was dispersed in pure water 3 together with a nonionic dispersion aid using a pulper, and then pure water 3 was added to dilute it to a predetermined concentration. Wet paper making using a machine, basis weight 18g / m ² , thickness 4
A 5 μm wet non-woven fabric was prepared. Both surfaces of the nonwoven fabric were heat treated in the same manner as in Example 6 to obtain a separator 8 for electrochemical element.

Example 9 Wet papermaking was carried out in the same manner as in Example 1 except that water 1 was used instead of pure water 1 to produce a wet nonwoven fabric having a basis weight of 18 g / m ² and a thickness of 45 μm. Both sides of the non-woven fabric were heat treated in the same manner as in Example 1 and then placed on a resin wire of 80 mesh and conveyed at 10 m / min, and the nozzle diameter was 10
5 μS / cm of conductivity from 5 nozzle plates with 1 μm nozzle with nozzle pitch of 0 μm and 1.2 mm pitch
Pure water 1 at 5 ° C. was poured to perform pure water flow treatment, and then dried to obtain a separator 9 for electrochemical element.

Example 10 Wet papermaking was carried out in the same manner as in Example 4 except that water 1 was used instead of pure water 1 to prepare a wet nonwoven fabric having a basis weight of 18 g / m ² and a thickness of 45 μm. Both sides of the non-woven fabric were heat treated in the same manner as in Example 4, and then placed on a resin wire of 80 mesh and conveyed at 10 m / min, and the nozzle diameter was 10
0 μm, nozzle pitch 1.2 mm, nozzles arranged in one row from 5 nozzle plates, conductivity 25 μS / cm,
Pure water 2 at 55 ° C. was poured to perform pure water flow treatment, and then dried to obtain a separator 10 for electrochemical element.

Comparative Example 1 Wet papermaking was carried out in the same manner as in Example 1 except that water 1 was used instead of pure water 1 to prepare a wet nonwoven fabric having a basis weight of 18 g / m ² and a thickness of 45 μm. Both sides of the non-woven fabric were heat treated in the same manner as in Example 1 to give a separator 11 for electrochemical device.
And

Comparative Example 2 Wet papermaking was carried out in the same manner as in Example 4 except that water 1 was used instead of pure water 1 to prepare a wet nonwoven fabric having a basis weight of 18 g / m ² and a thickness of 45 μm. Both sides of the non-woven fabric were heat treated in the same manner as in Example 4 to give a separator 12 for electrochemical device.
And

<Production of Non-Aqueous Electrolyte Batteries 1 to 12> 90% of coke powder having an average particle size of 6 μm and 10% of binder polytetrafluoroethylene were kneaded to prepare a negative electrode mixture. N-methylpyrrolidone was added to form a slurry, which was applied on both sides of a 100 μm-thick copper foil as a negative electrode current collector, dried and then compression-molded using a roller press machine to produce a 180 μm-thick negative electrode. did. A positive electrode mixture was prepared by kneading LiCoO ₂ having an average particle size of 6 μm in a compounding ratio of 90%, conductive graphite 6%, and binder 4%, and then a positive electrode current collector 20 μm thick aluminum foil was prepared. Was coated on both sides of the above, dried, and then compression-molded using a roller press machine to produce a positive electrode having a thickness of 150 μm. Electrochemical element separators 1 to 12 were laminated between a negative electrode and a positive electrode and spirally wound using a winding machine to produce a spiral wound element. This was housed in a nickel-plated cylindrical battery can. At this time, the negative electrode lead and the positive electrode lead were welded to the negative electrode terminal and the positive electrode terminal. Electrolyte solution was injected into the battery can, and the battery can and the battery lid were caulked and sealed to produce nonaqueous electrolyte batteries 1 to 12. As the electrolytic solution, a nonaqueous electrolytic solution was used in which LiPF ₆ was dissolved in a solvent in which propylene carbonate and diethyl carbonate were mixed at a volume ratio of 1: 1 so as to be 1 mol / l.

<Production of Electric Double Layer Capacitors 1-12>
Activated carbon 85% as an electrode active material, carbon black 7% as a conductive material, and polytetrafluoroethylene 8% as a binder were kneaded to prepare a sheet electrode having a thickness of 0.2 mm. This was adhered to both sides of an aluminum foil having a thickness of 50 μm using a conductive adhesive and rolled to prepare an electrode. This electrode was used as a positive electrode and a negative electrode. Electrochemical element separators 1 to 12 were laminated between a positive electrode and a negative electrode, and a spiral wound element was produced using a winding machine. A separator was placed on each of the outermost layers on the positive electrode side and the negative electrode side. The spiral wound element was housed in an aluminum case. Then, after the positive electrode lead and the negative electrode lead were welded to the positive electrode terminal and the negative electrode terminal attached to the case, the case was sealed leaving the electrolyte solution injection port. The case containing the spiral wound element was heated at 200 ° C. for 5 hours and dried. After allowing to cool, an electrolytic solution was injected into this case, and the injection port was tightly closed to produce electric double layer capacitors 1 to 12. For the electrolyte, 1.5 mo of propylene carbonate
l / such that l (C ₂ H _{5) 3} was used (CH ₃₎ NBF ₄ dissolved.

<Production of Aluminum Electrolytic Capacitors 1 to 12>
An aluminum foil having a thickness of 50 μm and an etching hole diameter of 1 to 5 μm was used as an electrode, and an anode connector was spot-welded to one surface of the electrode, then immersed in a boric oxygen solution kept at a temperature of 90 ° C., and an electric current of 30 A was applied for 15 minutes. The aluminum foil surface was oxidized for minutes to form an aluminum oxide dielectric layer. This was used as the anode. Similarly, a cathode connector was spot-welded to one surface of the aluminum foil electrode and used as a cathode. Electrochemical device separators 1 to 12 are placed on the dielectric layer of the anode, wound together with the cathode, and then inserted into a cell for an electrolytic capacitor, and an electrolytic solution (tetraethylammonium phthalate 24.1%, γ- After injecting 70% of butyrolactone and 5.9% of ethylene glycol), the cell was sealed to produce aluminum electrolytic capacitors 1 to 12.

The above-mentioned separators 1 to 1 for electrochemical devices
2, non-aqueous electrolyte batteries 1-12, electric double layer capacitor 1
.About.12 and aluminum electrolytic capacitors 1 to 12 were measured by the following test methods, and the results are shown in Table 1 below.

<Amount of Cationic Impurity> 2 g of each separator sample was ashed and dissolved by heating with 0.1 N nitric acid to ionize all the cationic impurities (Na, K, Mg, Ca), and the result was measured by ion chromatography. Measured and content (pp
m) is shown in Table 1 below.

<Capacity maintenance rate> A constant current of 0.5 CmA was applied to the nonaqueous electrolyte batteries 1 to 12 to charge them to 4.2V,
After reaching 4.2 V, the voltage was switched to a constant voltage so that the charging was completed in a total time of 2.5 hours. The discharge was carried out at a constant current of 0.5 CmA, and the initial discharge capacity when discharged until reaching 2.7 V was obtained. This charge and discharge is repeated 500 times,
The discharge capacity at the 500th time was determined, and the ratio to the initial discharge capacity was taken as the capacity retention rate, and shown in Table 1 below. The higher the capacity retention rate, the better the life characteristics.

<DC resistance> Electric double layer capacitors 1 to 1
After applying a direct current of 20 mA / cm ² to 2.5V and charging it to 2.5V, the current application was stopped and the voltage of the electric double layer capacitor after 1 hour was measured. Find the drop and divide it by the charging current to obtain D
The C resistance is shown in Table 1 below.

<Leakage Current> Electric Double Layer Capacitors 1 to 1
A direct current of 20 mA / cm ² was applied to No. ² to charge the battery to 2.5 V, and the leakage current immediately after charging was measured and shown in Table 1 below.

<Rise increase rate 1> Electric double layer capacitor 1
Continue to apply 2.5V at 45 ° C to ~ 12, measure the electrochemical device resistance after 2000 hours, divide by the resistance value at 0 hours, calculate the resistance increase rate (%), and increase the resistance. A rate of 1 is shown in Table 1 below. The smaller the rate of increase in resistance, the better the life characteristics.

<ESR> Aluminum electrolytic capacitors 1 to 12
ESR (equivalent series resistance) was measured using an LCZ meter under the condition of -40 ° C and 1 kHz, and the value is shown in Table 1 below.
It was shown to.

<Rise rise rate 2> Aluminum electrolytic capacitor 1
~ 12 hold at 105 ° C for 1000 hours, then cool,
ESR was measured in the same manner as <ESR>. From the ESR at this time, the rate of increase (%) with respect to the original ESR is shown as the resistance increase rate 2 in Table 1 below.

<Puncture Strength> A needle having a diameter of 1 mm and a radius R at the tip was lowered at a speed of 1 mm / s at right angles to the surface of each separator sample, and the load when penetrating the sample was defined as the puncture strength. The average value at each location was determined and shown in Table 1 below.

[0075]

[Table 1]

Evaluation: As shown in Table 1, Example 1
The separators for electrochemical devices produced in steps 1 to 8 are Na,
The content of K, Mg, Ca is 10ppm or less respectively, 5
The raw material is dispersed in pure water having a concentration of 5 ppm or less, 5 ppm or less, and 10 ppm or less, and is produced by a wet papermaking method using the pure water to make a cationic impurity (Na,
The total content of (K, Mg, Ca) is less than 1000 ppm, and the electrochemical element including the separator has a low resistance and a small leakage current, and the resistance hardly increases with time.
It had excellent life characteristics.

The electrochemical device separators produced in Examples 9 and 10 were produced by treating the nonwoven fabric with a pure water stream, so that cationic impurities (Na, K, Mg, Ca) were produced.
The total content of the above was less than 1000 ppm, and the electrochemical device including the separator had low resistance and small leakage current, resistance hardly increased with time, and excellent life characteristics.

The separators for electrochemical devices produced in Examples 4, 5, 7, 8 and 10 contained fibrillated cellulose or bacterial cellulose, and thus had excellent puncture strength and were excellent.

On the other hand, the separators for electrochemical devices produced in Comparative Examples 1 and 2 were cationic impurities (Na,
Since the total content of (K, Mg, Ca) is 1000 ppm or more, the electrochemical element provided with the separator had high internal resistance and poor life characteristics.

[0080]

As described above, according to the manufacturing method of the present invention, cationic impurities (Na, K, Mg, C) are used.
A separator for an electrochemical device having a total content of a) of less than 1000 ppm is obtained, and an electrochemical device provided with the separator has a low resistance, a small leakage current, and a resistance that does not easily increase with time. Excellent in characteristics.

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Claims (8)

[Claims] 1. A separator for an electrochemical element, which comprises a nonwoven fabric having a melting point or a thermal decomposition temperature of 250 ° C. or higher and at least a part of which has a fibrillated polymer having a fiber diameter of 1 μm or less, the separator being included in the nonwoven fabric. Total amount of cationic impurities (Na, K, Mg, Ca) generated is 1000 pp
A separator for an electrochemical element, which is less than m. 2. The separator for an electrochemical element according to claim 1, wherein the Ca content is less than 400 ppm and the K content is less than 100 ppm. 3. The separator for an electrochemical element according to claim 1, wherein the Na content is less than 400 ppm and the Mg content is less than 100 ppm. 4. A cationic impurity (Na, K, containing a polymer having a melting point or thermal decomposition temperature of 250 ° C. or higher and at least a part of which is fibrillated to a fiber diameter of 1 μm or less.
A method for producing a separator for an electrochemical device, comprising a nonwoven fabric having a total content of Mg, Ca) of less than 1000 ppm, wherein the content of each of Na, K, Mg and Ca is 10
ppm or less, 5 ppm or less, 5 ppm or less, 10 ppm
A method for producing a separator for an electrochemical element, comprising: dispersing a raw material in pure water, which is described below, and using the pure water to make water by a wet papermaking method. 5. A cationic impurity (Na, K, containing a polymer having a melting point or a thermal decomposition temperature of 250 ° C. or higher and at least a part of which is fibrillated to a fiber diameter of 1 μm or less.
A method for producing an electrochemical device separator comprising a non-woven fabric having a total content of Mg, Ca) of less than 1000 ppm, wherein the non-woven fabric is produced by treating the non-woven fabric with pure water. Production method. 6. The separator for an electrochemical element according to claim 1, wherein the electrochemical element is a non-aqueous electrolyte battery. 7. The separator for an electrochemical element according to claim 1, wherein the electrochemical element is an electric double layer capacitor. 8. The separator for electrochemical device according to claim 1, wherein the electrochemical device is an electrolytic capacitor.