JP2006344506A - Separator for electronic components - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a separator for electronic components having excellent mechanical strength in spite of a thin film in addition to excellent thermal shrinkage preventing property and ion conductivity. <P>SOLUTION: This separator for the electronic components have base materials 11, 12 with cavities formed inside, and a porous structure 13 made of resin is formed in cavities of base materials 11, 12 and/or on both faces or one face of the base material. The porous structure 13 is made porous by volatilizing a solvent from liquid including the resin forming the porous structure 13. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a separator provided in an electronic component such as a lithium ion secondary battery, a polymer lithium secondary battery, an aluminum electrolytic capacitor, an electric double layer capacitor, or a redox capacitor.

Electronic parts such as lithium ion secondary batteries, polymer lithium secondary batteries, aluminum electrolytic capacitors, electric double layer capacitors, and redox capacitors are equipped with a pair of electrodes and a separator, impregnated with an electrolyte, and are for industrial use. Or it is used for various electric and electronic equipment for consumer use.
As a separator provided in an electronic component, for example, in a lithium ion secondary battery and a polymer lithium secondary battery, a porous film such as polyolefin, polyester, polyamide, or polyimide, or a nonwoven fabric has been used. In aluminum electrolytic capacitors, electric double layer capacitors, and redox capacitors, paper made of cellulose pulp, cellulose fibers, polyester fibers, polyethylene terephthalate fibers, non-woven fabrics made of acrylic fibers, etc. have been used (for example, see Patent Documents 1 to 3). ).

  In order to improve the performance of electrical and electronic equipment, it is indispensable to further increase the capacity and functionality of electronic components. For this reason, improvements in separators are required. For example, in order to cope with an increase in capacity of electronic components, a separator having heat resistance, mechanical strength, and dimensional stability that can withstand abnormal heat generation such as self-heating during charging / discharging or abnormal charging is required. In addition, in order to improve the functionality of electronic components, in particular, to improve rapid charge / discharge characteristics and high output characteristics, there is a strong demand for separators that are thin and have improved uniformity.

For the purpose of satisfying these requirements, for example, Patent Document 4 discloses that a microporous film (stretched film) having a high air permeability produced by stretching a polyolefin is formed by forming a through hole with a needle or a laser. It has been proposed to use a separator having higher temper as a separator. Patent Document 5 proposes a separator in which a laminate in which two nonwoven fabrics are laminated is covered with a porous component, and the melting point of the resin constituting one nonwoven fabric is 180 ° C. or less.
JP 2000-285895 A JP 2001-1226697 A JP 2001-229908 A International Publication No. 01/67536 Pamphlet JP 2003-317893 A

When only the microporous film described in Patent Document 4 is used as a separator, since the air permeability is high, the electrolytic solution retainability is high and the ion conductivity is high. However, since the through-hole formed by a needle or a laser has a large hole diameter, the mechanical strength of the separator is low, and the separator is broken during manufacture or use, and the positive electrode and the negative electrode may be in direct contact and short-circuited. In particular, since a minute protrusion of several μm is formed on the electrode surface of a lithium ion secondary battery or a polymer lithium secondary battery, a minute short circuit is likely to occur due to breakage of the separator. Furthermore, when the separator breaks, the ion movement or the electron movement concentrates on the broken portion, so that the performance of the electronic component may be lowered.
Further, when a through-hole having a large hole diameter is formed, the electrode is easily contracted in a melt-down temperature range equal to or higher than the shutdown temperature, so that the electrodes are easily in direct contact with each other when the temperature becomes high.
Therefore, it is conceivable to reduce the porosity of the separator as a method for ensuring the mechanical strength after thinning the film. Cannot meet the demand for

Further, in the separator of Patent Document 5, since the melting point of the resin constituting one of the nonwoven fabrics is specified to be 180 ° C. or less, the heat resistance is insufficient, and when the temperature is increased, the resin contracts to fill the voids. . As a result, there was a portion without a separator between the electrodes, and the electrodes might be in direct contact and short-circuited. Therefore, it is not suitable for the use of an aluminum electrolytic capacitor or an electric double layer capacitor that requires a process of passing through a solder reflow furnace at 200 ° C. or higher.
Furthermore, in Patent Document 5, it is not described that two non-woven fabrics are bonded to each other, but it is estimated that the two non-woven fabrics are simply overlapped. In addition to the tendency to cause winding slippage, the interface between the nonwoven fabrics tends to have high internal resistance due to high electrical resistance.

  The present invention has been made in view of the above circumstances, and provides a separator for electronic parts that is excellent in heat shrinkage prevention and ion conductivity, and is excellent in mechanical strength despite being a thin film. Objective. It is another object of the present invention to provide an electronic component separator that is less likely to be unwound when wound and has a low internal resistance.

The separator for electronic components of the present invention is a separator for electronic components having a base material in which voids are formed,
A porous structure made of resin is formed in the voids of the base material and / or on both sides or one side of the base material,
The porous structure is characterized by being made porous by volatilizing a solvent from a liquid containing a resin that forms the porous structure.
In the electronic component separator of the present invention, two or more of the substrates may be laminated to form a laminate.
When two or more base materials are laminated, it is preferable that the porous structure is formed in the space of at least one base material.
In the separator for electronic parts of the present invention, the material of the substrate constituting the laminate is selected from polyethylene terephthalate, polybutylene terephthalate, polyamide, polyamideimide, polytetrafluoroethylene, polyimide, polyethylene naphthalate, and polyphenylene sulfide. 1 type is preferable.
In the separator for electronic parts of the present invention, the resin forming the porous structure is polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyethylene terephthalate, polybutylene terephthalate, polyamide, polyamideimide, polytetrafluoroethylene, polyimide. , Polyethylene naphthalate, and polyphenylene sulfide are preferable.
It is preferable that the base material in the electronic component separator of the present invention is a microporous film, and the microporous film has a through-hole formed in a direction perpendicular to the surface.
In the electronic component separator of the present invention, it is preferable that the porous structure contains filler particles.
The electronic component separator of the present invention is preferably provided in an electronic component selected from a lithium ion secondary battery, a polymer lithium battery, an aluminum electrolytic capacitor, and an electric double layer capacitor.

The separator for electronic parts of the present invention is excellent in heat shrinkage prevention and ion conductivity, and is excellent in mechanical strength despite being a thin film.
In the electronic component separator of the present invention, when two or more base materials are laminated to form a laminate, base materials having different characteristics can be combined, and thus functionality can be improved. Further, the separator can be easily thickened.
In the above case, if the porous structure is formed in the voids of at least one base material, it is possible to prevent the base material from being unwound when wound, and to reduce the internal resistance.
In the electronic component separator of the present invention, the material of the base material constituting the laminate was selected from polyethylene terephthalate, polybutylene terephthalate, polyamide, polyamideimide, polytetrafluoroethylene, polyimide, polyethylene naphthalate, and polyphenylene sulfide. If it is 1 type, thermal shrinkage can be made smaller and the solubility with respect to the organic solvent and ionic liquid which are used for electrolyte solution can be made low.
The resin forming the porous structure is selected from polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyethylene terephthalate, polybutylene terephthalate, polyamide, polyamideimide, polytetrafluoroethylene, polyimide, polyethylene naphthalate, and polyphenylene sulfide. If it is 1 type, electrical insulation can be made high.
If the base material is a microporous film and the microporous film has through-holes formed in a direction perpendicular to the surface, ions are likely to move, and ion conductivity is higher. can do.
When the porous structure contains filler particles, ion conductivity can be further increased.
The separator for electronic parts of the present invention is suitably used for electronic parts such as lithium ion secondary batteries, polymer lithium secondary batteries, aluminum electrolytic capacitors, electric double layer capacitors, and redox capacitors. In particular, it can be suitably used for large electronic components that require heat resistance.

An embodiment of an electronic component separator (hereinafter referred to as a separator) according to the present invention will be described.
FIG. 1 shows a cross-sectional view of the separator of this embodiment. This separator 1 has a laminated body 10 in which two base materials 11 and 12 having voids formed therein are laminated, and a porous structure 13 made of resin is placed in the gaps of the base materials 11 and 12. Is formed. In addition, filler particles 14, 14... Are included in the porous structure 13.

The base material 11 constituting the laminate 10 in this embodiment is a non-woven fabric in which a large number of short fibers are closely attached with gaps, and the base material 12 has a through hole 12a formed from one surface to the other surface. A microporous film.
Although it does not restrict | limit especially as a material of the base materials 11 and 12, Since heat shrink is small and it is hard to melt | dissolve with respect to the organic solvent and ionic liquid used for electrolyte solution, a polyethylene terephthalate, a polybutylene terephthalate, a polyamideimide, One type selected from polytetrafluoroethylene, polyimide, and polyethylene naphthalate is preferable. Among these, polyethylene terephthalate is preferable. When polyethylene terephthalate is used, the thermal shrinkage of the separator can be further reduced, and melting in the temperature range during overcharging and overheating can be suppressed, thereby further preventing a short circuit due to contact between the electrodes.

 Although the film thickness of the base materials 11 and 12 is suitably selected according to the use of the separator 1, it is preferable that it is thin at the point of thinning of an electronic component.

In the present invention, the gaps inside the nonwoven fabric forming the substrate and the through holes of the microporous film are collectively referred to as voids.
It is preferable that the ratio (void ratio) of the space | gap part in the base materials 11 and 12 is 20 to 90%, respectively, and 30 to 80% is more preferable. When the ratio of the voids in the base materials 11 and 12 is smaller than 20%, the ionic conductivity tends to be lowered, and when larger than 90%, the mechanical strength is lowered and the electrodes tend to be short-circuited. .

As shown in FIG. 2, the microporous film constituting the substrate 12 is a film in which a large number of through holes 12a, 12a,... Are formed on a stretched resin film with a needle or a laser.
When the microporous film is used for a lithium ion secondary battery or the like, a through-hole 12a is formed in a direction perpendicular to the surface 12b in order to smoothly move ions and reduce the internal resistance of the battery. It is preferable that As for the hole diameter of the through-hole 12a, 0.1-100 micrometers is preferable as an average hole diameter. If the average pore diameter of the through-holes 12a is less than 0.1 μm, the ion conductivity may be lowered, and if it exceeds 100 μm, the mechanical strength may be lowered to cause a short circuit. Moreover, it is preferable that the hole diameter of the through hole 12 a is appropriately selected according to the primary average particle diameter of the filler particles 14.

 The shortest distance between the adjacent through holes 12a and 12a in the microporous film is preferably 0.01 to 100 μm on average, and more preferably 0.1 to 50 μm. If the average shortest distance is less than 0.01 μm, the mechanical strength of the microporous film is low and may break during winding, but if it exceeds 100 μm, the mechanical strength is not a problem, When the hole diameter of the through hole 12a is small, the ion conductivity may be lowered.

  In the present invention, the average hole diameter of the through holes 12a and the average of the shortest distances between the adjacent through holes 12a and 12a are values obtained as follows. That is, first, the through holes 12a of the microporous film are observed with an electron microscope, and 100 through holes 12a are selected at random. And the hole diameter of these through-holes 12a is measured, the average value is calculated, and an average hole diameter is calculated | required. Similarly to the above, after 100 through holes 12a are selected at random, the shortest distance between the through holes 12a adjacent to each through hole 12a is measured, the average value is calculated, and the adjacent through holes 12a, 12a are measured. Find the average of the shortest distances between them.

As described above, the resin porous structure 13 is formed in the voids of the entire base material 11 and in the through holes 12 a of the base material 12.
Although it does not restrict | limit especially as resin which forms the porous structure 13, Since it has high electrical insulation, polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, polyethylene terephthalate, polybutylene terephthalate, polyamide, polyamideimide, polytetrafluoro One kind selected from ethylene, polyimide, polyethylene naphthalate, and polyphenylene sulfide is preferable. These resins are appropriately selected according to the heat resistance, dimensional stability, and mechanical strength required of the separator.

The porous structure 13 is made porous by volatilizing a solvent from a liquid containing a resin that forms the porous structure 13. In the porous structure 13 thus made porous, the pore diameter is smaller than that made porous by needle or laser drilling.
The pores of the porous structure 13 preferably have an average pore diameter of 0.1 to 15 μm, more preferably 0.5 to 5 μm, according to the bubble point method. When the average pore diameter of the pores is less than 0.1 μm, when the filler particles 14 are contained, the filler particles 14 may be extremely strongly agglomerated to lower the ion conductivity. On the other hand, when the thickness exceeds 15 μm, the mechanical strength may be lowered even when used at room temperature when the film is thinned, and the electrodes may be short-circuited.
Here, the hole diameter by the bubble point method is a value obtained using a polymeter manufactured by Seika Sangyo Co., Ltd.

Specific examples of filler particles 14 included in the porous structure 13 include electrically insulating inorganic particles such as natural silica, synthetic silica, alumina, titanium oxide, and glass, polytetrafluoroethylene, crosslinked acryl, benzoguanamine, crosslinked polyurethane, Organic particles such as cross-linked styrene and melamine are exemplified. Among these, since the clogging of the base material can be prevented and the performance degradation of the electronic component can be suppressed, it is preferable that the material is difficult to dissolve or gel in the electrolytic solution used for the electronic component. Moreover, in order to prevent the internal short circuit by the contact of filler particles 14, it is preferable that it is electrical insulation. Specifically, electrically insulating inorganic particles or polytetrafluoroethylene particles having excellent chemical resistance, heat resistance and dispersibility are preferred.
The shape of the filler particles 14 is not particularly limited, and may be any of an amorphous filler, a plate-like filler, a needle-like filler, and a spherical filler, but in terms of being able to uniformly disperse inside the porous structure 13, Spherical fillers are preferred.

The content of the filler particles 14 in the porous structure 13 is preferably 50 g / m ² or less, more preferably 30 g / m ² or less, based on the area of the separator 1. When the content of the filler particles 14 exceeds 50 g / m ² , the separator 1 tends to be too thick, or the impedance tends to be increased by inhibiting ion migration.

Although the thickness of the separator 1 can be increased by increasing the capacity of the electronic component by increasing the thickness of the electrode, the thickness of the entire electronic component can be decreased.
Specifically, the thickness of the separator 1 is preferably 30 μm or less, and more preferably 20 μm or less. When the thickness of the separator 1 is greater than 30 μm, the ion movement is hindered and the impedance tends to increase. However, when the electronic component is an electric double layer capacitor or the like, the separator 1 is preferably thick because it is necessary to hold a large amount of electrolyte.

A method for manufacturing the separator 1 will be described. Here, an example in which polyvinylidene fluoride is used as the resin for forming the porous structure 13 will be described.
First, polyvinylidene fluoride is dispersed in a good solvent in which it can be dissolved and dissolved to prepare a coating solution. Examples of the good solvent include N, N-dimethylacetamide, N, N-dimethylformamide, 1-methyl-2-pyrrolidone, N, N-dimethylsulfoxide and the like. Examples of the dispersion and dissolution method include a method using a commercially available stirrer.
Polyvinylidene fluoride can be easily dissolved in N, N-dimethylacetamide, N, N-dimethylformamide, 1-methyl-2-pyrrolidone, and N, N-dimethylsulfoxide at room temperature, so there is no need for heating. .
Thereafter, a poor solvent that does not dissolve polyvinylidene fluoride may be added to the coating solution. It is preferable to select a poor solvent having a boiling point higher than that of a good solvent. Examples of the poor solvent include dibutyl phthalate, ethylene glycol, diethylene glycol, glycerin and the like.
What is necessary is just to change suitably as a density | concentration of the polyvinylidene fluoride in a coating liquid according to the required characteristic of the separator obtained.

  The coating solution preferably has a water content of 0.7% by mass or less, more preferably 0.5% by mass or less, as measured by the Karl Fischer method. If the amount of water in the coating solution exceeds 0.7% by mass, gelation may proceed rapidly and the storage period of the coating solution may become extremely short. In addition, the porous structure formed may be extremely non-uniform, which may reduce the performance of the electronic component. Therefore, when a highly hygroscopic solvent is used as the solvent for the coating solution, it is preferable to pay particular attention to preventing moisture from entering.

Next, a non-woven fabric is placed on the support, and the coating solution is applied onto the non-woven fabric to contain polyvinylidene fluoride in the voids of the non-woven fabric. Here, examples of the support include resin films such as polypropylene and polyethylene terephthalate, glass plates, and the like. The support may be subjected to a surface treatment such as a mold release treatment or an easy adhesion treatment. Among the above supports, a resin film having flexibility is preferable. If the support is a resin film, the surface of the separator can be protected, and the separator can be wound and stored and transported while the separator is still laminated on the resin film.
Examples of the coating method of the coating liquid include a dip coating method, a spray coating method, a roll coating method, a doctor blade method, a gravure coating method, a screen printing method, or a coating method or a casting method.

Next, a microporous film is bonded to the surface of the nonwoven fabric to which the coating liquid has been applied. At this time, a part of the coating liquid inside the nonwoven fabric moves into the through hole of the microporous film.
And the solvent in a coating liquid is volatilized by drying. At this time, since the solvent contained in the resin passes through the resin and the portion through which the solvent has passed becomes pores, a porous structure can be formed.
Then, the separator 1 shown in FIG. 1 can be obtained by peeling the nonwoven fabric from the support. Such a separator manufacturing method is excellent in workability and productivity.
In addition, the separator of the present embodiment can be manufactured by a method other than the above manufacturing method, and for example, a support may not be used.

In the separator 1 of the embodiment described above, the porous structure 13 having a small hole diameter is formed in the gaps of the base materials 11 and 12 constituting the stacked body 10, so that the stacked body 10 is reinforced. be able to. Therefore, even if the film thickness is reduced, the mechanical strength is excellent, the separator 1 is prevented from being broken, and a short circuit due to direct contact between the electrodes is prevented. Furthermore, since the porous structure 13 is formed in the space between the base materials 11 and 12, the separator 1 is difficult to thermally shrink. Accordingly, even if heating or heat generation is performed, a direct short circuit between the electrodes at a high temperature can be prevented, so that the reliability of the electronic component can be increased.
In the present embodiment, the porous structure 13 positioned on the surfaces of the base materials 11 and 12 functions as an adhesive and can bond the two base materials 11 and 12 to each other. It is possible to prevent the winding slip when the operation is performed. Moreover, the electrical resistance of the interface between base materials can be lowered, and the internal resistance of the separator 1 can be lowered.
Moreover, since the dense layer is not formed in this separator 1, it is excellent in the retention property of electrolyte solution, and is excellent in ion conductivity. Moreover, since the porous structure 13 is uniformly formed inside the base materials 11 and 12 in the separator 1, the electrochemical reaction can be homogenized over the entire area of the electrode surface, and the ion conductivity is excellent, and the internal resistance Can be lower.

  Furthermore, in the separator 1, since the porous structure 13 contains the filler particles 14, it is possible to prevent formation of a dense layer (skin layer) that is not a porous structure, and to further improve ion conductivity and electronic conductivity. be able to. The reason for this is not clear, but during the manufacture of the separator, the solvent is unevenly distributed between the filler particles uniformly dispersed in the coating liquid and the resin interface, and preferentially porous around the filler particles. It is thought to progress. In addition, since the filler particles are uniformly dispersed on the surface and inside of the applied coating solution, it is assumed that the phase separation state tends to be uniform in the coating thickness direction, and the formation of a dense layer can be prevented as a whole. The

  The separator 1 according to the above-described embodiment is provided in an electronic component selected from a lithium ion secondary battery, a polymer lithium battery, an aluminum electrolytic capacitor, and an electric double layer capacitor because the effect of the present invention is particularly exerted. preferable.

Here, the lithium ion secondary battery and the polymer lithium secondary battery include a positive electrode, a negative electrode, and a separator provided therebetween, and include an electrode body that is wound or laminated. The electrode body is impregnated with a driving electrolyte and sealed with an aluminum case.
As the positive electrode, for example, a mixture obtained by mixing an active material, a lithium-containing oxide, and a binder such as polyvinylidene fluoride in 1-methyl-2-pyrrolidone is applied on an aluminum current collector. The thing which was done is mentioned. As the negative electrode, for example, a liquid mixture obtained by mixing a carbonaceous material capable of occluding and releasing lithium ions and a binder such as polyvinylidene fluoride in 1-methyl-2-pyrrolidone is applied onto a copper current collector. Are formed.

An aluminum electrolytic capacitor includes an electrode body in which a positive electrode foil and a negative electrode foil are wound or laminated with a separator interposed therebetween. The electrode body is impregnated with a driving electrolyte solution, and an aluminum case and a sealing body It is sealed. Examples of the positive electrode foil include an aluminum foil that has been etched and then subjected to chemical conversion to form a dielectric film. Examples of the negative electrode foil include an etched aluminum foil. Further, from the positive electrode foil and the negative electrode foil, the positive electrode lead and the negative electrode lead pass through the sealing body and are drawn out to the outside.
An electric double layer capacitor includes an electrode body in which a positive electrode and a negative electrode are wound or stacked with a separator interposed therebetween, and the electrode body is impregnated with a driving electrolyte, and an aluminum case and a sealing body It is sealed. Examples of the positive electrode and the negative electrode include those in which a mixture obtained by kneading activated carbon, a conductive agent, and a binder is attached to both surfaces of a current collector made of an aluminum sheet. Further, from the positive electrode foil and the negative electrode foil, the positive electrode lead and the negative electrode lead pass through the sealing body and are drawn out to the outside.

  The electronic component has a high capacity and a high function because the separator having excellent ion conductivity, low mechanical strength, and heat shrinkage prevention properties is disposed.

  Note that the present invention is not limited to the above-described embodiments. For example, in the embodiment described above, the filler particles 14 are included in the porous structure 13, but the filler particles may not be included in the porous structure 13. However, it is preferable that the filler particles 14 are included because ion conductivity can be further increased.

In the embodiment described above, the porous structure 13 is formed in the space between both of the two base materials 11 and 12, but as shown in FIG. 13 may be formed. Also in this case, the same effect as the above embodiment is exhibited.
In the embodiment described above, the porous structure 13 is formed only inside the base materials 11 and 12 made of nonwoven fabric. However, the porous structure 13 is formed on both surfaces or one surface of the laminate 10. It may be.
Furthermore, in the embodiment described above, the porous structure 13 is formed in the voids of the entire base materials 11 and 12, but the porous structure 13 may be formed in the voids of the base material and / or on both sides or on one side. It may be formed in at least a part of the above. However, since the short circuit between the electrodes can be further prevented, the heat shrinkage prevention property can be further improved, and the internal resistance can be further reduced, the porous structure is formed in the entire voids of the base materials 11 and 12 as in the above embodiment. Is preferably formed. For the same reason, when the porous structure is formed on both sides or one side, the porous structure is preferably formed on both sides or the entire surface of one side of the substrate.

  In the embodiment described above, the laminate 10 is a laminate of the two base materials 11 and 12, but in the present invention, the base material is not limited to two, and is one. Or three or more. However, in the case of one sheet, it is preferable to increase the thickness so as to ensure sufficient mechanical strength. When two or more base materials are laminated, it is possible to enhance the function of the separator by combining base materials having different characteristics, and it is possible to easily increase the thickness and to increase the mechanical strength. be able to. When five or more substrates are laminated, the internal resistance and impedance tend to increase in terms of performance, leading to cost increase in production, and thinning tends to be difficult, which is not preferable.

  The base materials 11 and 12 are not limited to a nonwoven fabric and a microporous film, and any material having voids inside may be used. In addition to the nonwoven fabric and the microporous film, a woven fabric or a mesh may be used. it can. That is, as the substrate, at least one selected from a nonwoven fabric, a woven fabric, a mesh, and a microporous film can be used.

  EXAMPLES Hereinafter, although the separator of this invention is demonstrated by an Example, this invention is not limited by these Examples.

Example 1
Polyvinylidene fluoride having a melting point of 170 ° C. was dissolved in N, N-dimethylacetamide (good solvent) to obtain a coating solution having a solid content concentration of 3% by mass. Next, a first nonwoven fabric made of polyethylene terephthalate having a porosity of 60% and a thickness of 13 μm was placed on a support made of polyethylene terephthalate. And the said coating liquid was apply | coated to the surface of the 1st nonwoven fabric by the casting method. Next, a second nonwoven fabric made of polyethylene terephthalate having a porosity of 60% and a thickness of 13 μm was laminated on the first nonwoven fabric to obtain a laminate, and then the solvent in the coating solution was evaporated by heat. The porous structure was formed in the voids in the first nonwoven fabric. Thereafter, the support was peeled from the laminate and removed to obtain a separator having a thickness of 30 μm.

(Example 2)
Polyvinylidene fluoride having a melting point of 170 ° C. was dissolved in N, N-dimethylacetamide (good solvent) to obtain a coating solution having a solid content concentration of 3% by mass. Next, a nonwoven fabric made of polyethylene terephthalate having a porosity of 55% and a thickness of 13 μm was placed on a support made of polyethylene terephthalate. And the said coating liquid was apply | coated to the surface of the nonwoven fabric by the casting method. Next, a microporous film made of polyethylene terephthalate having a porosity of 40% and a thickness of 8 μm was laminated on the nonwoven fabric to obtain a laminate, and then the solvent in the coating solution was evaporated by heat to create a laminate. A porous structure was formed in the voids. Thereafter, the support was peeled off from the laminate, and a separator having a thickness of 23 μm was obtained.

(Example 3)
After dissolving polyvinylidene fluoride in N, N-dimethylacetamide (good solvent) and then adding dibutyl phthalate (poor solvent) to obtain a coating solution, except that the thickness of the second nonwoven fabric was 15 μm Obtained a separator having a thickness of 32 μm in the same manner as in Example 1.

Example 4
After dissolving polyvinylidene fluoride in N, N-dimethylacetamide (good solvent), dibutyl phthalate (poor solvent) was added to obtain a coating solution, the porosity of the nonwoven fabric was 65%, microporous A separator having a thickness of 21 μm was obtained in the same manner as in Example 2 except that the porosity of the conductive film was 40% and the thickness was 6 μm.

(Example 5)
Polyvinylidene fluoride having a melting point of 170 ° C. was dissolved in N, N-dimethylacetamide (good solvent), and dibutyl phthalate (poor solvent) was added to obtain a coating solution having a solid content concentration of 3% by mass. Next, a first microporous film made of polyethylene terephthalate having a porosity of 40% and a thickness of 6 μm was placed on a support made of polyethylene terephthalate. And the said coating liquid was apply | coated to the surface of the 1st microporous film by the casting method. Next, a second microporous film made of polyethylene terephthalate having a porosity of 40% and a thickness of 8 μm was laminated on the first microporous film to obtain a laminate, and then the solvent in the coating solution Was evaporated by heat to form a porous structure in the through hole in the first microporous film. Thereafter, the support was peeled off from the laminate, and a separator having a thickness of 17 μm was obtained.

(Example 6)
Instead of a non-woven fabric made of polyethylene terephthalate with a porosity of 65% and a thickness of 13 μm, a non-woven fabric made of polyamideimide with a porosity of 60% and a thickness of 15 μm was used, and a microporous made of polyethylene terephthalate with a porosity of 40% and a thickness of 6 μm. A separator having a thickness of 26 μm was obtained in the same manner as in Example 4 except that a microporous film made of polyethylene terephthalate having a porosity of 40% and a thickness of 8 μm was used instead of the porous film.

(Example 7)
After adding dibutyl phthalate (poor solvent), polytetrafluoroethylene particles having a primary average particle size of 0.5 μm are added, and the solid content concentration is 3 mass% (the filler particles in the solid content are 50 mass%). A separator having a thickness of 32 μm was obtained in the same manner as in Example 3 except that this coating solution was used.

(Example 8)
After adding dibutyl phthalate (poor solvent), polytetrafluoroethylene particles having a primary average particle size of 0.5 μm are added, and the solid content concentration is 3 mass% (the filler particles in the solid content are 50 mass%). The coating liquid was obtained and used, and a non-woven fabric made of polyethylene terephthalate with a porosity of 60% and a thickness of 15 μm was used instead of a non-woven fabric made of polyethylene terephthalate with a porosity of 65% and thickness of 13 μm. Except for this, a separator having a thickness of 32 μm was obtained in the same manner as in Example 4.

Example 9
After adding dibutyl phthalate (poor solvent), polytetrafluoroethylene particles having a primary average particle size of 0.5 μm are added, and the solid content concentration is 3 mass% (the filler particles in the solid content are 50 mass%). The coating liquid was obtained and used, and instead of a microporous film made of polyethylene terephthalate with a porosity of 40% and a thickness of 8 μm, a fine film made of polyethylene terephthalate with a porosity of 40% and a thickness of 6 μm was used. A separator having a thickness of 16 μm was obtained in the same manner as in Example 5 except that the porous film was used.

(Example 10)
A separator having a thickness of 21 μm was obtained in the same manner as in Example 4 except that polyamideimide having a melting point of 250 ° C. was used instead of polyvinylidene fluoride having a melting point of 170 ° C.

(Example 11)
Dibutyl phthalate (poor solvent) was added to an N, N-dimethylacetamide (good solvent) solution in which polyimide having substantially no melting point was dissolved to obtain a coating solution having a solid content concentration of 3% by mass. Next, a first nonwoven fabric made of polyethylene terephthalate having a porosity of 65% and a thickness of 13 μm was placed on a support made of polyethylene terephthalate. And the said coating liquid was apply | coated by the casting method on the 1st nonwoven fabric. Next, a second nonwoven fabric made of polyethylene terephthalate having a porosity of 65% and a thickness of 13 μm is laminated on the first nonwoven fabric to obtain a laminate, and then the solvent in the coating solution is evaporated by heat. A porous structure was formed inside the second nonwoven fabric. Thereafter, the support was peeled off from the laminate, and a separator having a thickness of 29 μm was obtained.

(Comparative Example 1)
The separator of Comparative Example 1 is a polyethylene stretched porous film having a thickness of 20 μm that is widely used for separators of conventional lithium ion secondary batteries.
(Comparative Example 2)
The separator of Comparative Example 2 is a nonwoven fabric made of cellulose pulp having a thickness of 30 μm, which is widely used for separators of conventional electric double layer capacitors.
(Comparative Example 3)
The separator of Comparative Example 3 is a nonwoven fabric made of polyethylene terephthalate having a porosity of 60% and a thickness of 13 μm.
(Comparative Example 4)
The separator of Comparative Example 4 is a microporous film made of polyethylene terephthalate having a porosity of 40% and a thickness of 8 μm.

The following characteristics were evaluated for the separators of Examples 1 to 11 and Comparative Examples 1 to 4.
<Heat-resistant dimensional stability (prevents heat shrinkage)>
The separators of Examples and Comparative Examples were cut to obtain 5 × 5 cm square test pieces. Next, the test piece was sandwiched between two glass plates having a length of 10 cm, a width of 10 cm, and a thickness of 5 mm, and then placed horizontally on a bat made of aluminum. And it was left to stand in 150 degreeC, 200 degreeC, and 250 degreeC oven for 1 hour, respectively, and the area by heat was measured. Area maintenance rate = (Area after test / Area before test: 25 cm ² ) × 100 (%) was evaluated as an index of heat-resistant dimensional stability. The results are shown in Table 1. In addition, it is excellent in heat-resistant dimensional stability, so that an area maintenance factor is large.

<Short-circuit prevention (mechanical strength)>
The separators (5 × 5 cm) of Examples and Comparative Examples were sandwiched between two stainless steel plates (3 × 3 cm), and pressure was applied so that both electrodes were in close contact with a potential difference of 80 V between the stainless steel electrodes. And the pressure when it short-circuited (when an electrical resistance value became substantially 0 ohm) was measured, and this was made into short circuit pressure. The test was performed 5 times, and the average value was obtained. The results are shown in Table 2. In addition, it shows that it is excellent in short circuit prevention property (it is hard to short-circuit), so that short circuit pressure is high.

<Ion conductivity>
The ionic conductivity of the separator was measured by an AC impedance method. Specifically, after the separators of Examples 1 to 11 and Comparative Examples 1 and 2 were vacuum impregnated in an electrolytic solution in which (C ₂ H ₅ ) ₄ BF ₄ was dissolved in propylene carbonate at a concentration of 1 mol / l, An electrode and a separator were incorporated into a simple cell, and measurement was performed at 20 ° C. At this time, an electrode for an electric double layer capacitor manufactured by Hosen Co., Ltd. was used as the electrode. The results are shown in Table 2.

As shown in Table 1, the separators of Examples 1 to 11 in which the porous structure is formed inside the substrate have good heat-resistant dimensional stability, excellent short-circuit prevention properties, and ion conductivity. It was excellent. Therefore, the separators of Examples 1 to 11 can sufficiently meet the demand for higher capacity and higher functionality of electronic components.
On the other hand, the separator of Comparative Example 1 made of a polyethylene stretched porous film was completely melted at 200 ° C. and did not maintain its shape at all, and its heat-resistant dimensional stability was extremely low. Moreover, short circuit prevention property and ion conductivity were also low.
The separator of Comparative Example 2 made of a cellulose pulp nonwoven fabric had low heat-resistant dimensional stability, short-circuit prevention, and low ionic conductivity.
The separator of Comparative Example 3 made of a nonwoven fabric made of polyethylene terephthalate and the separator of Comparative Example 4 made of a microporous film made of polyethylene terephthalate are excellent in heat-resistant dimensional stability, but have low mechanical strength and short-circuit between electrodes. Occurred and the ionic conductivity could not be measured.
Therefore, it is difficult for the comparative separator to satisfy the demand for higher capacity and higher functionality of electronic components.

It is a figure which shows typically the cross section of one embodiment of the separator for electronic components of this invention. It is a top view which shows an example of a microporous film. It is a figure which shows typically the cross section of the other embodiment of the separator for electronic components of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Separator 10 Laminated body 11,12 Base material 12a Through-hole 12b Surface 13 Porous structure 14 Filler particle

Claims (8)

An electronic component separator having a base material in which a void is formed,
A porous structure made of resin is formed in the voids of the base material and / or on both sides or one side of the base material,
A separator for electronic parts, wherein the porous structure is made porous by volatilizing a solvent from a liquid containing a resin forming the porous structure.   The separator for electronic components according to claim 1, wherein two or more base materials are laminated to form a laminate.   The separator for an electronic component according to claim 2, wherein the porous structure is formed in a gap in at least one substrate.   The material of the base material is one selected from polyethylene terephthalate, polybutylene terephthalate, polyamide, polyamideimide, polytetrafluoroethylene, polyimide, polyethylene naphthalate, and polyphenylene sulfide. The separator for electronic components of any one of these.   The resin forming the porous structure is selected from polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyethylene terephthalate, polybutylene terephthalate, polyamide, polyamideimide, polytetrafluoroethylene, polyimide, polyethylene naphthalate, and polyphenylene sulfide. The electronic component separator according to claim 1, wherein the electronic component separator is one type.   The said base material is a microporous film, and this microporous film is a thing by which the through-hole is formed in the orthogonal | vertical direction with respect to the surface. The separator for electronic components as described in 2.   The separator for an electronic component according to any one of claims 1 to 6, wherein the porous structure contains filler particles. The electronic component separator according to any one of claims 1 to 7, which is provided in an electronic component selected from a lithium ion secondary battery, a polymer lithium battery, an aluminum electrolytic capacitor, and an electric double layer capacitor.

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