JP2015149223A - polymer membrane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method for easily obtaining a polymer membrane excellent in ion conductivity, and a polymer membrane obtained by the production method.SOLUTION: A polymer membrane contains a resin constituting a polymer membrane, an ionic liquid, and surface-modified fine particles.

Description

  The present invention relates to a polymer membrane.

  Ion conductive materials are key materials in the electrochemical field, and have been deeply involved in the environment and energy fields since ancient times. At present, high-performance ions are used to improve power generation and charge / discharge efficiency, safety and durability in electrochemical devices (energy devices) such as secondary batteries, fuel cells, and electrochemical capacitors. Conductive materials are being developed domestically and abroad.

JP 2009-59659 WO2011 / 049113 Publication

Takahiro Ichikawa; Masafumi Yoshio; Atsushi Hamasaki; Tomohiro Mukai; Hiroyuki Ohno; Takashi Kato; J. Am. Chem. Soc. 2007, 129, 10662-10663. Jae-Hong Choi; Yuesheng Ye; Yossef A. Elabd; Karen I. Winey; Macromolecules 2013, 46, 5290-5300. Takaya Sato; Takashi Morinaga; Shoko Marukane, Takuya Narutomi; Tatsuya Igarashi; Yuko Kawano, Kohji Ohno; Takeshi Fukuda; Yoshinobu Tsujii; Adv. Mater. 2011, 23, 4868-4872.

  However, various polymer membranes as ion-conducting materials have been studied, but a technique for easily obtaining a polymer membrane with an ion conduction path (particularly, a polymer membrane in which an ionic liquid and a polymer are combined). There are almost no examples. As one of the few examples of composite membranes containing ionic liquids, a technique for creating polymer cross-linked gels containing ionic liquids is also conceivable. However, in this technique, ionic conduction is improved by gelation rather than the original ionic liquid itself. There is a problem that the performance is significantly reduced.

  Therefore, an object of the present invention is to provide a production method for easily obtaining a polymer membrane excellent in ion conductivity and a polymer membrane obtained by the production method.

  As a result of intensive studies, the present inventors have achieved a polymer membrane that uses a specific component in combination to achieve the above-mentioned purpose, and an ionic liquid conduction path has been established (that is, excellent ionic conductivity). The present inventors have found that a polymer film can be obtained and have completed the present invention.

That is, the present invention relates to the following polymer film, a method for producing the polymer film, and an electrochemical device having the polymer film.
1. A polymer film comprising a resin, an ionic liquid, and surface-modified fine particles constituting the polymer film.
2. Item 2. The polymer film according to Item 1, wherein the surface-modified fine particle is a composite fine particle comprising a polymer brush layer comprising a polymer graft chain formed by polymerizing a monomer having a polymerizable functional group.
3. Item 3. The polymer film according to Item 2, wherein the polymer graft chain is made of at least one selected from the group consisting of polystyrene and polystyrene derivatives.
4). Item 4. The polymer film according to any one of Items 1 to 3, wherein the resin constituting the polymer film is at least one selected from the group consisting of polystyrene, polystyrene derivatives, polyimides, and polyimide derivatives.
5. Item 5. The polymer film according to any one of Items 1 to 4, wherein the ionic liquid is 1-ethyl-3-methylimidazolium-bis (trifluoromethylsulfonyl) imide.
6). Item 6. The polymer film according to any one of Items 1 to 5, wherein the content of the ionic liquid is greater than the content of the surface-modified fine particles.
7). Item 7. The polymer film according to any one of Items 1 to 6, wherein the content of the surface-modified fine particles is 1 to 20% by mass with respect to the entire polymer film.
8). Item 8. The polymer film according to any one of Items 1 to 7, wherein the content of the ionic liquid is 20 to 80% by mass with respect to the entire polymer film.
9. Item 9. The polymer film according to any one of Items 1 to 8, wherein the content of the resin constituting the polymer film is 10 to 90% by mass with respect to the entire polymer film.
10. A method for producing a polymer film comprising a resin constituting the polymer film, an ionic liquid, and surface-modified fine particles, comprising the following steps 1-3:
(i) Step 1 of preparing a resin composition for producing a polymer film comprising a resin constituting the polymer film, an ionic liquid, surface-modified fine particles, and a solvent;
(ii) Step 2 of applying the resin composition; and
(iii) Step 3 of forming the polymer film by vaporizing a solvent in the resin composition;
A method for producing a polymer film, comprising:
11. 10. An electrochemical device having the polymer film according to any one of items 1 to 9.
12 Item 12. The electrochemical device according to Item 11, wherein the electrochemical device is an electrochemical capacitor or a secondary battery.

Definition of Terms Here, terms of the present specification are defined.

  “Ionic liquid” is a low melting point salt having ionic conductivity, also called an ionic liquid or a room temperature molten salt, many of which are organic onium ions as cations and organic or inorganic as anions. It means that having a characteristic of a comparatively low melting point obtained by combining with an anion. The melting point is usually 100 ° C. or lower, preferably room temperature (25 ° C.) or lower.

  “Surface-modified fine particles” mean fine particles in which a modified product (eg, a polymer graft chain described later) is chemically bonded to the fine particle surface. Not fine particles) ”and is used separately.

  The “composite fine particles” mean those formed by bonding polymer graft chains to the surface of the fine particles.

  “Polymer brush layer” means a polymer graft layer in which a large number of polymer graft chains are bonded to the surface of fine particles in a state having a high density and an anisotropic shape perpendicular to the surface. . The “polymer graft chain” is not limited to a homopolymer of a monomer alone, but also includes a random copolymer or a block copolymer of a plurality of different monomers.

  “Surface occupancy” refers to the number of polymer chains per monomer cross-sectional area on the surface of fine particles. Furthermore, the “bond” means a bond formed by a general chemical reaction, and specifically includes a covalent bond and an ionic bond.

  “Molecular weight distribution index” refers to the ratio of Mw (weight average molecular weight) / Mn (number average molecular weight).

  “Polymer membrane” is a structure in which the structure has a self-supporting shape and volume, resists the force applied from the outside, does not flow, and is self-supporting at temperatures above room temperature. It is a certain solid film. An example of a method for expressing a force that resists external force is breaking strength.

Method for Measuring Parameters Next, methods for measuring various main parameters defined in this specification will be listed.

(Method for measuring graft density and surface occupancy)
The graft density is calculated from the absolute value of Mn (number average molecular weight) of the graft chain, the amount of grafted polymer (graft amount), and the specific surface area of the fine particles. The absolute value of Mn is determined by gel permeation chromatography or polymerization rate, the graft amount is determined by thermogravimetric analysis or various spectroscopic methods, and the specific surface area is calculated from the particle size of fine particles. The surface occupancy is calculated by obtaining the cross-sectional area from the repeating unit length in the fully extended form of the polymer and the bulk density of the polymer (or monomer) and multiplying by the graft density. Here, the theoretical maximum value of the graft density depends on the size of the monomer (cross-sectional area of the polymer). The maximum graft density is small for large size monomers. On the other hand, the surface occupancy is the graft density per monomer cross-sectional area (polymer cross-sectional area), and the maximum value is 100% by correcting the difference in monomer size (polymer thickness). Occupancy rate means the proportion of the surface occupied by graft points (first monomer) (100% with closest packing, and cannot be grafted beyond this).

(Breaking strength)
The sample is left in a thermostatic chamber at 23 ° C. and 65% for 12 hours or more, and then cut into a width of 5 mm and a length of 50 mm. Then, based on JIS K7113, the breaking strength of the cut sample is measured using a precision universal testing machine AGS-1KNG manufactured by Shimadzu Corporation.

(Ionic conductivity)
Create a sample (polymer film) on a comb-shaped electrode, apply an AC voltage of 10 mV to a lead wire directly attached to the electrode while changing the voltage from 10 MHz to 10 Hz using an LCR meter, and response of current and phase angle Measure. The ionic conductivity is obtained from the intercept of the Cole-Cole plot with the real axis by a generally used method. In this measurement, the sample is placed in a constant temperature and humidity chamber and measured at a predetermined temperature.

(Weight average molecular weight, number average molecular weight)
Mw (weight average molecular weight) and Mn (number average molecular weight) of the graft polymer are assumed to be obtained by cutting out the graft polymer from the silica particles by hydrofluoric acid treatment, or the free polymer produced during polymerization has the same molecular weight as the graft polymer. Then, it is estimated by gel permeation chromatography. The absolute value of Mn is calculated from the polymerization rate.

≪ １． Polymer membrane of the present invention >>
The polymer film of the present invention contains a resin constituting the polymer film, an ionic liquid, and surface-modified fine particles. The polymer membrane of the present invention is also referred to as an ionic liquid-containing blend membrane or simply a polymer membrane.

  Here, each component of resin, ionic liquid, and surface-modified fine particles constituting the polymer film, and physical properties of the polymer film of the present invention will be described below. It should be noted that the contents of the patents, patent applications, and documents cited in this specification should be incorporated as references to this specification in the same manner as the contents themselves are described in this specification.

Resin constituting the polymer film The polymer film of the present invention contains a resin constituting the polymer film (hereinafter also referred to as a matrix polymer).

  The type of base material resin is not particularly limited as long as it contains a ionic liquid and surface-modified fine particles and can form a polymer film. For example, any of a thermoplastic resin and a thermosetting resin can be used. . Specific matrix resins include polystyrene or derivatives thereof, polyacrylic acid or derivatives thereof, polymethacrylic acid or derivatives thereof, polyacrylamide or derivatives thereof, polymethacrylamide or derivatives thereof, polyacrylonitrile, polyimide or derivatives thereof, poly Examples thereof include lactic acid or derivatives thereof, polyvinyl acetate, polyvinyl alcohol, polyethylene oxide, and polycarbonate. A preferable base material resin is at least one selected from the group consisting of polystyrene, polystyrene derivatives, polyimides and polyimide derivatives. A commercially available product can be used as the base material resin. Each physical property (for example, weight average molecular weight) of the base resin is not particularly limited as long as a polymer film can be formed. The matrix resin can be used alone or in combination of two or more.

  The content of the base resin is not particularly limited as long as the polymer film can be formed, but is preferably 10 to 90% by mass with respect to the entire polymer film, and 20 to 80% by mass with respect to the entire polymer film. More preferably, it is more preferably 25 to 50% by mass with respect to the entire polymer membrane.

Ionic liquid The polymer membrane of the present invention contains an ionic liquid. The ionic liquid has characteristics such as flame retardancy, high heat resistance, and high ionic conductivity.

The ionic liquid is not particularly limited. For example, examples of the cation include ionic liquids such as quaternary ammonium salts, imidazolium salts, pyridinium salts, pyrrolidinium salts, quaternary phosphonium salts, guanidinium salts, isouronium salts, and thiouronium salts. Examples of the _{anion, N (CF 3 SO 2)} 2 - {TFSI}, BF 4 -, PF 6 -, BF 3 CF 3 - , and the like. As the ionic liquid, 1-ethyl-3-methylimidazolium-bis (trifluoromethylsulfonyl) imide (EMI-TFSI) is particularly preferable. A commercial item can be used for the ionic liquid. The ionic liquids can be used alone or in combination of two or more.

  The content of the ionic liquid is preferably larger than the content of the surface-modified fine particles described later. When the content of the ionic liquid is larger than the content of the surface-modified fine particles, an ion conduction path due to the network structure of the ionic liquid is more suitably formed in the polymer film. Specifically, the content of the ionic liquid is preferably 20 to 80% by mass with respect to the entire polymer film, more preferably 30 to 70% by mass with respect to the entire polymer film, and relative to the entire polymer film. More preferred is 40 to 65% by mass.

Surface-modified fine particles The polymer film of the present invention contains surface-modified fine particles.

  As the surface-modified fine particles, composite fine particles having a polymer brush layer made of a polymer graft chain formed by polymerization of a monomer having a polymerizable functional group (hereinafter also simply referred to as composite fine particles having a polymer brush layer or composite fine particles) Is preferred. In the composite fine particles provided with the polymer brush layer, polymer graft chains made of monomers as raw materials are bonded to the surface of the fine particles at a very high density via bonding groups. As a result, the graft chain takes an anisotropic form due to steric repulsion between adjacent graft chains, and forms a polymer brush. Here, the composite fine particles including the polymer brush layer are divided into “polymer graft chain part”, “fine particle part”, and “bonding base part”, and these will be described in order. Thereafter, the structure and physical properties of the composite fine particles will be described in detail.

( Polymer graft chain )
The polymer graft chain part is composed of a homopolymer of a monomer alone, a random copolymer or a block copolymer of a plurality of different monomers.

  The monomer constituting the polymer graft chain homopolymer or copolymer (random copolymer or block copolymer) is not particularly limited. For example, styrene or a derivative thereof, acrylic acid or a derivative thereof, methacrylic acid or a derivative thereof, acrylamide Alternatively, derivatives thereof, methacrylamide or derivatives thereof, ionic liquid monomers, vinyl acetate, acrylonitrile, ethylene oxide, and the like can be given. The above-mentioned copolymer is a polymer obtained by appropriately combining the above monomers.

  The ionic liquid monomer is not particularly limited as long as it has a polymerizable functional group and an ionic group. Here, the raw material ionic liquid monomer is quaternary ammonium salt polymerizable ionic liquid, imidazolium salt polymerizable ionic liquid, pyridinium salt polymerizable ionic liquid, pyrrolidinium salt polymerizable ionic liquid, quaternary phosphonium type Examples thereof include a polymerizable ionic liquid, a guanidinium salt-based polymerizable ionic liquid, an isouronium salt-based polymerizable ionic liquid, and a thiouronium salt-based polymerizable ionic liquid. In particular, ammonium salt type ionic liquids have higher voltage resistance than imidazolium salt or pyridinium salt type ionic liquids. That is, it has a low reductive decomposition potential and a high oxidative decomposition potential, is stable in a wide voltage range, and a quaternary ammonium salt-based polymerizable ionic liquid is preferable because of its wide potential window and low viscosity. In particular, an ammonium salt type ionic liquid having a relatively short alkyl group of about C1 to C5 is more suitable because of its low viscosity.

  In addition, the ionic liquid monomer which is a raw material may have other functional groups in addition to the polymerization group and the ionic group. For example, in order to achieve higher proton conductivity, those having strong acid groups (for example, sulfonic acid groups) may be used. In order to achieve higher proton conductivity, the ionic liquid monomer having a strong acid group may be used in combination with another monomer having a strong acid group.

  Since the composite fine particles are preferably manufactured by living radical polymerization, it is preferable that the polymerizable functional group is a radical polymerizable functional group. In particular, an acryloyl group, a methacryloyl group, or a vinyl group is preferable. Among the monomers constituting the above-mentioned polymer graft chain homopolymer or copolymer, at least one selected from the group consisting of styrene and styrene derivatives is particularly suitable (that is, the polymer graft chain is polystyrene and polystyrene derivatives). It is particularly preferred that it consists of at least one selected from the group consisting of:

  The weight average molecular weight of the polymer graft chain is not particularly limited, but is preferably 1000 to 300,000, more preferably 2000 to 100,000, and still more preferably 4000 to 70,000. It is preferable that the weight average molecular weight is appropriately determined according to the raw materials used, applications, and the like. Furthermore, the molecular weight distribution index of the polymer graft chain is preferably 1.5 or less, more preferably 1.3 or less, and even more preferably 1.2 or less.

( Fine particle part )
Next, the fine particles used for the composite fine particles including the polymer brush layer are not particularly limited, and may be an inorganic substance or an organic substance. For example, silicon oxide such as silica; noble metals such as Au (gold), Ag (silver), Pt (platinum), Pd (palladium); Ti, Zr, Ta, Sn, Zn, Cu, V, Sb, In, Examples thereof include transition metals such as Hf, Y, Ce, Sc, La, Eu, Ni, Co, and Fe, inorganic substances such as oxides or nitrides thereof, or organic substances such as polymers. The fine particles are core portions in the composite fine particles including the polymer brush layer.

The average particle size of the fine particles, which are the core portions, is preferably 5 nm to 30 μm, more preferably 10 nm to 10 μm, and even more preferably 10 nm to 1 μm, in order to perform graft polymerization from the surface of the fine particles with ultra high density. The fine particles are preferably “fine particles with a narrow particle size distribution” having a particle size variation of 20% or less. Specifically, the variation in particle diameter is the following formula (1):
Variation in particle diameter (%) = σ × 100 / d _mean (1)
(In the formula (1), σ is a standard deviation and d _mean is an average particle diameter). The standard deviation σ is the following equation (2):

It is represented by In the present specification, the average particle size of the fine particles of the core portion indicates an average particle size based on mass (volume basis) measured by a dynamic light scattering method. It is obtained by measuring with an automatic light scattering type particle size / particle size distribution measuring device. The concept of particle size variation and the measurement method are also described in JP-A-2006-208453.

  The polymer brush chain length can be controlled by a free length in the range of about 3 nm to 100 μm. The range of the polymer brush chain length is preferably 3 nm to 1 μm, more preferably 3 nm to 100 nm. The diameter range of the composite fine particles including the polymer brush chain (polymer brush layer) is preferably about 10 nm to 30 μm, more preferably 10 nm to 20 μm, further preferably 15 nm to 10 μm, and particularly preferably 20 nm to 3 μm. .

( Bonding base )
Next, the bonding group used for the composite fine particle having the polymer brush layer is not particularly limited as long as it binds the fine particle surface and the polymer graft chain. Here, the compound used as the raw material of the bonding group is a compound having a group bonded to the surface of the fine particles and a polymerization initiating group for living radical polymerization. For example, when silica is selected as the fine particles, an example of the raw material compound is, for example, the following formula:

(In the formula, the spacer chain length n is preferably an integer of 1 to 10, more preferably an integer of 3 to 8, most preferably 6, R ₁ is preferably C1 to C3 alkyl, and C1. R ₂ is preferably C 1 or C 2 alkyl; X is preferably a halogen atom, and particularly preferably Br). The polymerization initiating group-containing silane coupling agent can be produced, for example, according to the method described in WO2006 / 087839. Typical polymerization initiation group-containing silane coupling agents include, for example, (2-bromo-2-methyl) propionyloxyhexyltriethoxysilane (BHE), (2-bromo-2-methyl) propionyloxypropyltriethoxysilane ( BPE) and the like. In addition, from a viewpoint of graft density adjustment, in addition to a polymerization initiating group-containing silane coupling agent, a silane coupling agent that does not contain a polymerization initiating group (for example, a commonly used alkylsilane coupling agent) may be used. In addition, when the fine particle itself already has a polymerization initiation site (for example, when it originally has, or when it is formed as a result of surface treatment by plasma treatment or the like), the bonding base is present. (It can be said that the fine particles have a bonding base).

( Structure of composite fine particles with polymer brush layer )
In the composite fine particles, polymer graft chains made from a monomer having a polymerizable functional group as a raw material are bonded to the surface of the fine particles at a very high density via a bonding group (brush shape). Here, the surface occupation ratio of the graft chains on the surface of the fine particles is preferably a high density of several percent or more, more preferably 5 to 50%, and still more preferably 10 to 40%. By setting the graft density within such a range, the graft chain takes an anisotropic form (highly stretched form).

  The average particle size of the composite fine particles is preferably 10 nm to 30 μm, more preferably 10 nm to 20 μm, further preferably 15 nm to 10 μm, and particularly preferably 20 nm to 3 μm. The composite fine particles are preferably “composite fine particles with a narrow particle size distribution” having a particle size variation of 20% or less. The variation in the particle diameter is expressed by the above equation (1), and the standard deviation σ is expressed by the above equation (2), similarly to the variation in the particle diameter of the fine particles at the core. In the present specification, the average particle size of the composite fine particles indicates an average particle size based on mass (volume basis) measured by a dynamic light scattering method, and various commercially available dynamic light scattering particles. Obtained by measuring with a diameter / particle size distribution measuring device. The concept of particle size variation and the measurement method are also described in JP-A-2006-208453.

  As described above, the content of the surface-modified fine particles is preferably smaller than the content of the ionic liquid in order to more suitably form an ion conduction path based on the network structure of the ionic liquid in the polymer film. Specifically, the content of the surface-modified fine particles is preferably 1 to 20% by mass with respect to the entire polymer film, more preferably 3 to 15% by mass with respect to the entire polymer film, and the entire polymer film. 5 to 10% by mass is more preferable. The surface-modified fine particles can be used alone or in combination of two or more.

Other Components The polymer film of the present invention contains other components to the extent that the effects of the present invention are not impaired, if necessary, in addition to the resin, ionic liquid, and surface-modified fine particles constituting the polymer film. May be. Examples of other components include lithium ions, protons, and other ions.

(lithium ion)
When the polymer film of the present invention contains lithium ions, high lithium ion conductivity can be imparted. Here, as the addition of lithium ion (lithium salt) is not particularly limited, for _{example, LiN (CF 3 SO 2)} 2 - {LiTFSI}, LiBF 4, LiPF 6, LiClO 4, LiAsF 6, LiSbF 6, LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , Li (CF ₃ SO ₂ ) ₃ C, LiBPh ₄ (Ph is phenyl), and the like.

(proton)
When the polymer membrane of the present invention contains a strong acid as a proton, high proton conductivity can be imparted. Here, the strong acid to be added is not particularly limited, and examples thereof include sulfuric acid, benzenesulfonic acid, trifluoroacetic acid, trifluoromethanesulfonic acid, and phosphoric acid compounds (such as phosphoric acid and polyphosphoric acid).

(Other ions)
The polymer film of the present invention may contain other ions. Examples of other ions include ions necessary for driving an electrochemical device. More specifically, halogen ions such as iodine ions can be mentioned. In addition, ammonium ions, phosphorus ions, organic salts or inorganic salts for general electric double layer capacitors, and the like can also be used as other ions.

  It should be noted that the ionic liquid contained in the polymer membrane of the present invention also functions as a cation and an anion in a dissociated state. When the polymer film of the present invention is used for an electric double layer capacitor, the ionic liquid functions as carrier ions.

Structure of Polymer Film of the Present Invention The structure of the polymer film of the present invention will be described based on the evaluation described later and FIGS.

The photograph of the specific polymer film of this invention is shown in FIG.3 and FIG.4. In the polymer membrane of the present invention, the matrix resin and the ionic liquid are not macroscopically separated, but the matrix resin and the ionic liquid are not completely mixed. That is, the polymer film of the present invention has a structure in which phase separation between the base resin and the ionic liquid is blocked by the surface-modified fine particles (that is, a structure in which the base resin and the ionic liquid are micro-phase separated). It is thought that it has formed. Specifically, as shown in FIG. 7, (1) the matrix resin phase and the ionic liquid phase each form an independent network structure, and (2) the surface-modified fine particles are It is considered that each network structure is stabilized by segregating at the interface between the network structure of the material resin phase and the network structure of the ionic liquid phase. The reason why the surface-modified fine particles segregate at the interface is considered to be due to the surface modification of the fine particles. In particular, when the surface-modified fine particles are composite fine particles having the polymer brush layer, it is considered that the matrix resin and the composite fine particles are not mixed due to the size exclusion effect of the polymer brush layer (FIG. 8).
Regarding these points, in reference evaluation, poly (methyl methacrylate) (PMMA) and poly (styrene-r-acrylonitrile) (also referred to as SAN or PSAN) are used as a base resin, and PMMA brush-added silica fine particles (PMMA) As a result of observing the internal structure of the blend film to which -SiP) was added with an atomic force microscope (AFM), PMMA-SiP was segregated at the interface between PMMA and PSAN (Fig. 8). Further, as shown in FIG. 5, the polymer film of Comparative Example 1 that does not contain surface-modified fine particles macroscopically phase-separates the base resin and the ionic liquid, thereby forming a stable film. It is also suggested that it is not possible.

Physical properties of the polymer membrane of the present invention (ion conductivity)
The higher the ionic conductivity of the polymer membrane of the present invention, the better. However, in reality, a conductivity of 0.08 mS · cm ⁻¹ or more at 35 ° C. is preferable. Further, it is preferably 0.1 mS · cm ⁻¹ or more, and more preferably 0.5 mS · cm ⁻¹ or more. Preferred for the superlative is 1 mS · cm ⁻¹ or more. This ionic conductivity shows high conductivity equivalent to that of a bulk ionic liquid while being solid. The reason why the polymer film of the present invention has such high ion conductivity is considered to be that an ion conduction path is formed by the network structure of the ionic liquid by the structure of the polymer film described above.

(Shape retention)
The polymer membrane of the present invention exhibits a self-supporting non-flowable solid state at least in the range of room temperature to 150 ° C. A more preferable form retention temperature range is from room temperature to 250 ° C. The upper limit is not particularly limited, but it is preferable that the solid state can be maintained up to the thermal decomposition temperature of the brush chain polymer.

(Mechanical strength)
The mechanical strength (breaking strength) of the polymer film of the present invention is not particularly limited, but the tensile breaking strength is preferably 0.05 kgf / cm ² or more in the above temperature range (the temperature range described in the column of shape retention), More preferably, it is 0.1 kgf / cm ² or more.

(Film thickness)
The thickness of the polymer film of the present invention is not particularly limited and can be appropriately set according to the purpose of use. For example, the thickness of the polymer film of the present invention is preferably 1 to 500 μm.

≪ 2. Method for Producing Polymer Film of the Present Invention >>
The method for producing the polymer film of the present invention comprises:
(i) Step 1 of preparing a resin composition for producing a polymer film comprising a resin constituting the polymer film, an ionic liquid, surface-modified fine particles, and a solvent;
(ii) Step 2 of applying the resin composition; and
(iii) Step 3 of forming the polymer film by vaporizing a solvent in the resin composition;
It is characterized by including.
According to the production method, the polymer film of the present invention containing the resin, the ionic liquid, and the surface-modified fine particles constituting the polymer film can be suitably and easily produced.

  Here, each step will be described in detail below.

Process 1
In step 1, a resin composition for producing a polymer film containing a resin constituting the polymer film, an ionic liquid, surface-modified fine particles, and a solvent (and other components as necessary) is prepared.

  As the resin constituting the polymer film, each resin described in the above-mentioned item of polymer film can be used. Further, as the ionic liquid, each ionic liquid described in the item of the polymer film can be used.

  The solvent is not particularly limited as long as the resin, the ionic liquid, and the surface-modified fine particles constituting the polymer film can be dissolved or dispersed. Specific examples of the solvent include tetrahydrofuran (THF), acetone, chloroform, dichloromethane, toluene, benzene, chlorobenzene, dichlorobenzene, ethyl acetate, dimethylformamide, dimethyl sulfoxide, dimethylacetamide, N-methylpyrrolidone, and the like. It is done.

  The content of the solvent in the resin composition is not particularly limited as long as the resin constituting the polymer film, the ionic liquid, and the surface-modified fine particles can be dissolved or dispersed, but with respect to the entire resin composition 5-99 mass% is preferable.

  Although the dissolution (or dispersion) temperature in preparation of the said resin composition is not specifically limited, 0-100 degreeC is preferable.

  The surface-modified fine particle is not particularly limited as long as it is a fine particle in which a modified product is chemically bonded to the surface of the fine particle. As the surface-modified fine particles, composite fine particles having the above-described polymer brush layer are preferable.

  Each compounding ratio of the resin, the ionic liquid, and the surface-modified fine particles constituting the polymer film is the same as each compounding ratio (mass ratio) described in the item of the polymer film.

  Here, a method for producing composite fine particles having the aforementioned polymer brush layer, which is suitable as surface-modified fine particles, will be described below.

< Method for producing composite fine particles having polymer brush layer >
The method for producing the composite fine particles having the polymer brush layer is not particularly limited, for example,
(A) a first step in which a compound serving as a raw material for the bonding base is reacted with the fine particles to form a polymerization initiating group on the surface of the fine particles;
(B) A crude product containing composite fine particles in which a polymer graft chain is bonded to the surface of the fine particles with ultra-high density by bringing the monomer having a polymerization initiating group on the surface into contact with the monomer under living radical polymerization conditions. Two steps; and
(C) The composite fine particles can be suitably obtained by a production method including the third step of refining the crude product in the second step to obtain composite fine particles. Hereinafter, each process is explained in full detail.

( First step of the method for producing composite fine particles having a polymer brush layer )
In the first step, the compound serving as the raw material for the bonding base is reacted with the fine particles to form a polymerization initiating group on the surface of the fine particles. The first step can be performed by a known method. For example, when an inorganic / metal material (for example, silica) is used as fine particles and a polymerization initiating group-containing silane coupling agent is used as a compound as a raw material for the bonding group, the silane coupling agent is hydrolyzed in the presence of water. To form silanol and partially condensed to an oligomer state. In this state, after adsorbing on the silica surface by hydrogen bonding, the inorganic / metal material is dried to cause a dehydration condensation reaction to form a polymerization initiating group on the material.

  Here, the graft density on the surface of the fine particles can be freely changed by adjusting the ratio of the polymerization initiation group-containing silane coupling agent and the silane coupling agent not containing the polymerization initiation group. When all of the silane coupling agents are polymerization initiation group-containing silane coupling agents, a surface occupancy of more than 10% can be achieved after the following polymerization.

( Second step of manufacturing method of composite fine particles having polymer brush layer )
In the second step, the polymer graft chains are bonded to the surface of the fine particles with ultra-high density by contacting the fine particles having a polymerization initiating group on the surface (obtained in the first step) and the monomer under living radical polymerization conditions. A crude product containing the obtained composite fine particles is obtained. Specifically, it is carried out by polymerizing monomer raw materials (styrene or a derivative thereof, acrylic acid or a derivative thereof, methacrylic acid or a derivative thereof, an ionic liquid monomer, or the like) under living radical polymerization conditions. In addition, the kind of monomer to be used may be single or plural.

Here, the living radical polymerization is a polymerization reaction that has no chain transfer reaction and termination reaction or is negligibly small, and retains the polymerization activity at the end of the produced polymer even after the completion of the polymerization reaction. The polymerization means that the polymerization reaction can be started again. As a feature of living radical polymerization,
(a) A polymer having an arbitrary average molecular weight can be synthesized by adjusting the concentration ratio of the monomer and the polymerization initiator,
(b) the molecular weight distribution of the resulting polymer is very narrow,
(c) that it can be applied to block copolymers;
Etc. As used herein, “living radical polymerization conditions” refers to polymerization conditions appropriately selected by those skilled in the art so that living radical polymerization based on a polymerization initiating group provided on the surface of fine particles proceeds reliably and satisfactorily. Means that.

  Here, when forming a graft chain using an ionic liquid monomer, it is particularly preferable to perform polymerization by an atom transfer radical polymerization method (ATRP) or a reversible transfer catalyst polymerization method (RTCP). The catalyst used in the atom transfer radical polymerization method is not particularly limited. For example, a monovalent copper catalyst such as copper (I) chloride and two molar equivalents of bipyridine (bpy) to the copper catalyst are used. A combination with a ligand of a locus is mentioned. Furthermore, it is preferable to add copper (II) dichloride to the combination. According to this method, the number average molecular weight Mn can be easily increased in proportion to the polymerization rate while maintaining a narrow molecular weight distribution index (for example, less than 1.3). As a result, the molecular weight controlled ionic liquid polymer Synthesis and molecular weight control in the molecular weight range from thousands to hundreds of thousands are possible. The catalyst used in the reversible transfer catalytic polymerization method is not particularly limited, and examples thereof include a combination of a carbon catalyst such as 1,4-cyclohexadiene and a radical generator. According to this method, particularly excellent amino group resistance is exhibited. Here, when the molecular weight of the ionic liquid polymer is increased, the glass transition temperature increases while the ionic conductivity tends to decrease. Therefore, it is necessary to optimize the molecular weight while taking into consideration the characteristics (ion conductivity) of the electrolyte membrane and taking into account the mechanical properties of the membrane.

( Third step of the method for producing composite fine particles having a polymer brush layer )
The target composite fine particles are obtained by subjecting impurities (unreacted raw materials, by-products, solvents, etc.) from the crude product (reaction solution) obtained in the second step to a method commonly used in the art (for example, extraction, After removal by distillation, washing, concentration, precipitation, filtration, drying, etc.), followed by a combination of post-treatment methods commonly used in the field (for example, adsorption, elution, distillation, precipitation, precipitation, chromatography, etc.) Can be isolated.

Process 2
In step 2, the resin composition obtained in step 1 is applied.

  Examples of the application of the resin composition include a solvent casting method, a dip coating method, a squeegee method (doctor blade method), an ink jet method, and a screen printing method.

  In step 2, the resin composition is usually applied on the substrate. The base material is not particularly limited, and examples thereof include various ceramics (eg, glass) and polymer films. In addition, when producing an electrochemical device having the polymer membrane of the present invention as an electrolyte membrane or a separator, it may be applied on the surface of the negative electrode or the positive electrode and used as it is after Step 3.

Process 3
In step 3, the solvent in the resin composition applied in step 2 is vaporized to form a polymer film containing the resin constituting the polymer film, the ionic liquid, and the surface-modified fine particles.

  The solvent can be vaporized by a conventional drying method such as drying at normal temperature or drying by heating.

  Although the drying temperature in the vaporization of the solvent can be appropriately determined according to the type of the solvent and the like, it is usually in the range of 10 ° C to 150 ° C, preferably in the range of 20 ° C to 50 ° C.

  The drying time for vaporization of the solvent can also be appropriately determined according to the type of the solvent and the like, but is usually in the range of 30 seconds to 1 hour, preferably in the range of 1 minute to 30 minutes.

≪ 3. Application of polymer membrane of the present invention >>
The polymer membrane of the present invention can be used in various technical fields. In particular, the polymer membrane of the present invention can be suitably used as an electrolyte membrane or a separator.

Electrochemical Device of the Present Invention The present invention also includes an electrochemical device using the polymer membrane of the present invention as an electrolyte membrane or a separator. Examples of electrochemical devices include primary batteries, secondary batteries (eg, lithium ion secondary batteries, nickel metal hydride secondary batteries, organic radical batteries, etc.), fuel cells (eg, polymer electrolyte fuel cells (PEFC), etc.) ), Solar cells (eg, dye-sensitized solar cells, etc.), electrochemical capacitors (eg, electric double layer capacitors, redox capacitors, hybrid capacitors, etc.). That is, the polymer membrane of the present invention can be used in the same manner as the electrolyte membrane or separator used in the known electrochemical device. For example, by setting the polymer film of the present invention so that the polymer film of the present invention is located between the positive electrode and the negative electrode, an electrochemical device having the polymer film of the present invention (of the present invention) is obtained. Can do.

  Here, a lithium ion secondary battery will be described as an example of an electrochemical device. The lithium ion secondary battery as an electrochemical device of the present invention has, for example, a negative electrode, a positive electrode, and the polymer film of the present invention sandwiched between the negative electrode and the positive electrode. The negative electrode is composed of, for example, a current collector and a negative electrode material layer. The negative electrode material layer is obtained by drying the negative electrode paste applied to the surface of the current collector. The negative electrode paste includes a negative electrode active material, a conductive material, a solvent, a binder polymer, and the like. The positive electrode is composed of, for example, a current collector and a positive electrode material layer. The positive electrode material layer is obtained by drying the positive electrode paste applied to the surface of the current collector. The positive electrode paste includes a positive electrode active material, a conductive material, a solvent, a binder polymer, and the like.

  When the secondary battery is a bipolar battery, it has a negative electrode and a positive electrode, and the negative electrode material layer is formed on one surface of the current collector via the polymer film of the present invention between the negative electrode and the positive electrode. And a bipolar electrode having a positive electrode material layer formed on the other surface. When the cells are stacked with the bipolar electrode interposed therebetween, the voltage can be increased in the same manner as when the cells are connected in series. There is no theoretical limit to the number of stacked layers in the bipolar battery.

As the negative electrode active material is not particularly limited, for example, it may be used an electrode active material of oxide of Li ₄ Ti ₅ O ₁₂ system, and the like. Further, as the negative electrode active material, in addition to the above oxide-based electrode active materials, carbon / graphite-based materials, alloy materials such as Sn, Al, Zn, Si, and lithium metal-based materials can be used. is there.

As the positive electrode active material is not particularly limited, for example, lithium cobaltate (LiCoO _2), lithium nickelate (LiNiO _2), nickel - cobalt oxide _{(LiNi 1-x Co x O} 2), lithium manganate (LiMn ₂ O ₄ ), nickel-manganese oxide (LiNi _0.5 Mn _0.5 O ₂ ), nickel-manganese-cobalt oxide (LiNi _1/3 Mn _1/3 Co _1/3 O ₂ ) Non-oxide type olivine type lithium iron phosphate (LiFePO ₄ ), lithium iron silicate type oxide (Li ₂ Fe _1-x Mn _x SiO ₄ ), Li ₂ MnO ₃ , Li _1.2 Fe _0.4 Examples thereof include Li ₂ MO ₃ oxides such as Mn _0.4 O ₂ and oxide electrode active materials such as sulfur compounds (Li ₂ S).

  The conductive material is not particularly limited as long as it can impart conductivity to the carbonaceous material. For example, carbon black, ketjen black, acetylene black, carbon whisker, carbon fiber, natural graphite, artificial graphite, titanium oxide Metal fibers such as ruthenium oxide, aluminum, and nickel can be used, and one of these can be used alone or in combination of two or more. Among these, ketjen black and / or acetylene black which is a kind of carbon black is preferable.

  As the binder polymer, for example, an unsaturated polyurethane compound, a polymer material having an interpenetrating network structure or a semi-interpenetrating network structure, a polyester-based thermoplastic resin, or a fluorine-based polymer material is preferably used. Since these polymer materials have high adhesiveness, the physical strength of the electrode can be improved. In addition, the fluorine-based polymer material is excellent in thermal and electrical stability.

  The solvent may be an organic solvent or water, and is appropriately selected from known solvents.

  Regarding the composition of the positive electrode or negative electrode paste (ink), the content of the positive electrode active material or the negative electrode active material is preferably 20 to 70% by mass of the total mass of the ink, for example. In addition, the content of the conductive material is preferably 2 to 15% by mass with respect to the total mass of the ink. The content of the binder polymer is preferably 2 to 20% by mass with respect to the total mass of the ink.

  The ink is used by being applied to a current collector. Although it does not specifically limit as a collector, For example, aluminum foil or aluminum oxide is mentioned as a positive electrode collector. On the other hand, examples of the negative electrode current collector include a copper foil, a nickel foil, and a metal foil whose surface is formed of a copper plating film or a nickel plating film.

  Next, an electrode manufacturing process will be described. First, the ink material is spread on a current collector such as an aluminum foil so as to have a uniform thickness, thereby constructing an electrode material layer. Here, although the thickness of an electrode part is not specifically limited, 5-1000 micrometers is suitable. Although it should be controlled according to the use of the electrochemical device, it is generally preferable to set the thickness to about 10 to 200 μm. Next, if necessary, a frame may be formed around the electrode material layer constructed by applying the ink in order to prevent liquid leakage. The frame body is not particularly limited, but for example, it is preferable to form the frame body around the electrode using an ultraviolet curable resin. Here, although it does not specifically limit as ultraviolet curable resin, For example, acrylic resin and methacrylic resin etc. can be used. Subsequently, for example, in accordance with the method for producing a polymer film of the present invention, the polymer film of the present invention is formed by applying and drying a resin composition for polymer film production on an electrode.

  In the case where the electrode is a bipolar electrode, the bipolar electrode in which the positive electrode and the negative electrode are combined on the front and back sides is manufactured by bonding the positive and negative electrode current collectors prepared by the above method. Then, a positive electrode, a bipolar electrode, and a negative electrode are laminated in this order, and a terminal is joined to the lowermost positive electrode and the uppermost negative electrode. Here, it is preferable to cover the top and bottom of the laminate with a polypropylene plate.

  When the electrochemical device of the present invention is an electric double layer capacitor, the arrangement of the electrode and the polymer film of the present invention can be the same as that of the secondary battery. In addition, a method for manufacturing an electrode as an electric double layer capacitor includes applying an electrode paste containing an electrode material (for example, a carbon material, a metal oxide material, a conductive polymer material, etc.), a binder polymer, and a solvent to a current collector. And dried. About the binder polymer and solvent in an electrode paste, and a collector, the thing similar to the binder polymer and solvent in the said secondary battery, and what was illustrated by the collector can be used, respectively.

When the polymer membrane of the present invention is used as a separator, the electrolyte solution of the electrochemical device of the present invention can be appropriately selected from known solvents. For example, water, an aprotic solvent, the ionic liquid exemplified in the section of the polymer membrane of the present invention, and the like can be mentioned. As aprotic solvents, ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, formic acid Examples include methyl, methyl acetate, methyl propionate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, and sulfolane. As the solute in the electric double layer capacitor is not particularly limited, for _{example, H 2 SO 4, KOH,} Et 4 NBF 4, Et 4 NPF 6, Et 4 PBF 4, Et 3 MeNBF 4 and the like (the Et is ethyl and Me is methyl). Moreover, as the solute (lithium salt) in the lithium ion secondary battery, the lithium ions (lithium salt) exemplified in the item of the polymer film of the present invention can be used. The above-mentioned electrolytic solution and solute can be used alone or in combination of two or more.

  The polymer membrane of the present invention is excellent in ion conductivity because an ion conduction path by an ionic liquid is constructed. Moreover, the manufacturing method of the polymer film of this invention can manufacture the polymer film of this invention excellent in the said ion conductivity easily.

FIG. 2 is a schematic diagram of composite fine particles including surface-modified fine particles and a polymer brush layer including a polymer graft chain obtained by polymerizing a monomer having a polymerizable functional group. Each characteristic of the composite fine particle provided with a polymer brush layer composed of a polymer graft chain obtained by polymerizing a monomer having a polymerizable functional group is shown. The polymer film obtained in Example 1 is shown. The polymer film obtained in Example 2 is shown. The polymer film obtained in Comparative Example 1 is shown. The SEM photograph which observed the polymer film obtained in Example 1 by evaluation 2 is shown. The schematic diagram of each structure of base material resin, an ionic liquid, and surface-modified fine particles contained in the polymer film of the present invention is shown. AFM image of PMMA / PSAN blend film with silica fine particles added with PMMA brush, suggesting that surface-modified fine particles segregate at the interface between the matrix resin phase network structure and the ionic liquid phase network structure. Indicates. The length of one side of the AFM image is 20 μm. Moreover, the schematic diagram of the size exclusion effect of composite fine particle provided with a polymer brush layer is shown.

  The present invention will be specifically described below with reference to examples and comparative examples. However, the present invention is not limited to the examples.

Production example (production of surface-modified fine particles)
1. Process for forming polymerization initiating groups on the surface of silica fine particles In a 500 mL eggplant-shaped flask, silica fine particles (manufactured by Aldrich, HS-30, 4 g), ethanol (250 mL), triethylamine (4.2 g), (2-bromo-2 -Methyl) propionyloxypropyltriethoxysilane (BPE, 7.8 g) was added and stirred at room temperature for 3 days. Thereafter, ethanol was removed under reduced pressure, acetone (40 mL) was added to the residue to dissolve, and hexane (700 mL) was further added to recover a white precipitate. The white precipitate was dissolved in dimethylformamide (DMF, 20 mL). This was used as a polymerization initiating group-provided silica fine particle dispersion.

2. Process of grafting polystyrene onto polymerization initiator group-attached silica fine particles Styrene (19 g) containing silica fine particles (2 wt%) with polymerization initiator groups, Cu (I) Cl (90 mg), dinonylbipyridine (750 mg) ), Ethyl 2-bromoisobutyrate (EBIB; 36 mg) was placed in a Pyrex (registered trademark) glass tube, degassed by a freeze-thaw method, sealed in a vacuum, and then polymerized at 100 ° C. for 24 hours. Monomer conversion was determined by NMR and was 40%. The purification of the grafted silica fine particles was performed by repeating centrifugation and redispersion in THF. The graft polymer was cut from the silica fine particles by treating the grafted silica fine particles with hydrogen fluoride. The number average molecular weight (Mn) and molecular weight distribution (Mw / Mn) of the graft polymer were determined by gel filtration chromatography. As a result, Mn = 28000 and Mw / Mn = 1.20. Using the graft amount and molecular weight determined by thermogravimetry, the graft density was calculated to be 0.35 / nm ² .

Example 1 (Production of polymer membrane)
By mixing the following components (1) to (4), a solution containing a resin (matrix resin) constituting the polymer film, an ionic liquid, and surface-modified fine particles was prepared.
<Solution components>
(1) Base material resin: polystyrene (manufactured by Aldrich, Mw to 280,000) 3.5 parts by mass,
(2) Ionic liquid: 1-ethyl-3-methylimidazolium-bis (trifluoromethylsulfonyl) imide (EMI-TFSI, manufactured by Tokyo Chemical Industry Co., Ltd.) 6 parts by weight)
(3) Surface-modified fine particles: composite fine particles (polystyrene-added silica fine particles) having a polymer brush layer made of polystyrene graft chains prepared in Production Example, 0.5 parts by mass,
(4) Solvent: 90 parts by mass of tetrahydrofuran (THF).
Subsequently, the said solution was directly apply | coated at room temperature by the solvent cast method on the glass substrate, and the coating film was formed. Next, the coating film was placed in a vacuum atmosphere at 50 ° C. for 1 hour to evaporate THF in the coating film and dry the coating film. As a result, a cloudy polymer film was obtained.

Example 2 (Production of polymer membrane)
A pale yellow polymer film was obtained in the same manner as in Example 1, except that polyimide was used as the base material resin and N-methylpyrrolidone was used as the solvent instead of THF.

Comparative Example 1
A white turbid polymer film was obtained in the same manner as in Example 1 except that the polystyrene-added silica fine particles were not used.

Evaluation 1 (visual observation)
In Examples 1 and 2, although the ionic liquid content in the polymer membrane is 50 wt% or more, as shown in FIGS. 3 and 4, as shown in FIGS. Molecular film) was obtained. On the other hand, in Comparative Example 1, as shown in FIG. 5, the matrix resin and the ionic liquid phase-separated macroscopically, and a stable film could not be formed. In addition, it is thought that the ionic liquid existed in the hole of FIG.

Evaluation 2 (observation with measuring instrument)
The polymer films obtained in Examples 1 and 2 were immersed in methanol for 24 hours to remove the ionic liquid contained in each polymer film. Next, the polymer films were frozen by immersing the polymer films in liquid nitrogen for 3 minutes. Next, each frozen polymer film was broken, and the broken section was observed with a scanning electron microscope (SEM, trade name: S-3400N, manufactured by Hitachi, Ltd.). As a result, it was revealed that co-continuous pores exist inside each polymer membrane (FIG. 6). It is considered that an ionic liquid was present in this hole.

Evaluation 3 (conductivity measurement)
As a result of measuring the ionic conductivity of the polymer membrane of Example 1 according to the measurement method described above, it was 10 ⁻³ S · cm ⁻¹ (at 25 ° C.). This ionic conductivity was not significantly different from the ionic conductivity of bulk EMI-TFSI (about 10 ⁻² S · cm ⁻¹ (at 25 ° C.)). This result is thought to be because the network structure of the ionic liquid contributed as an efficient ion conduction path.

Reference evaluation (AFM measurement)
Composite fine particles (PMMA brush-applied silica fine particles, PMMA-SiP) provided with a polymer brush layer composed of a PMMA graft chain were prepared according to the description in “Method for producing composite fine particles provided with polymer brush layer” in this specification. Next, after preparing PMMA / PSAN as a base material resin, except that no ionic liquid is used, PMMA-PSAN is compared with PMMA / PSAN as described in “Method for producing polymer film of the present invention” in this specification. A film to which SiP was added was obtained. As a result of observing the internal structure of the film with an atomic force microscope (AFM), it was found that PMMA-SiP was segregated at the interface between PMMA and PSAN.

1. Surface-modified fine particles (composite fine particles with a polymer brush layer comprising polymer graft chains formed by polymerizing monomers having a polymerizable functional group)
2. Fine particle part (core)
3. Surface modification part (polymer graft chain part)
4). Hole 5. Base material resin (phase)
6). Ionic liquid (phase)

Claims (12)

  A polymer film comprising a resin, an ionic liquid, and surface-modified fine particles constituting the polymer film.   2. The polymer film according to claim 1, wherein the surface-modified fine particles are composite fine particles including a polymer brush layer composed of a polymer graft chain formed by polymerizing a monomer having a polymerizable functional group.   The polymer film according to claim 2, wherein the polymer graft chain is composed of at least one selected from the group consisting of polystyrene and polystyrene derivatives.   The polymer film according to any one of claims 1 to 3, wherein the resin constituting the polymer film is at least one selected from the group consisting of polystyrene, polystyrene derivatives, polyimides, and polyimide derivatives.   The polymer film according to claim 1, wherein the ionic liquid is 1-ethyl-3-methylimidazolium-bis (trifluoromethylsulfonyl) imide.   The polymer film according to claim 1, wherein the content of the ionic liquid is larger than the content of the surface-modified fine particles.   The polymer film according to any one of claims 1 to 6, wherein the content of the surface-modified fine particles is 1 to 20 mass% with respect to the entire polymer film.   The polymer film according to any one of claims 1 to 7, wherein a content of the ionic liquid is 20 to 80% by mass with respect to the entire polymer film.   The polymer film according to any one of claims 1 to 8, wherein a content of the resin constituting the polymer film is 10 to 90% by mass with respect to the entire polymer film. A method for producing a polymer film comprising a resin constituting the polymer film, an ionic liquid, and surface-modified fine particles, comprising the following steps 1-3:
(i) Step 1 of preparing a resin composition for producing a polymer film comprising a resin constituting the polymer film, an ionic liquid, surface-modified fine particles, and a solvent;
(ii) Step 2 of applying the resin composition; and
(iii) Step 3 of forming the polymer film by vaporizing a solvent in the resin composition;
A method for producing a polymer film, comprising:   An electrochemical device comprising the polymer film according to claim 1.   The electrochemical device according to claim 11, wherein the electrochemical device is an electrochemical capacitor or a secondary battery.

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