JPH10199330A - Aprotic electrolyte thin film and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain aprotic electrolyte thin film capable of immobilizing electrolyte solution stable in a wide temperature range and controllable in ion conductivity by impregnating and immobilizing aprotic electrolyte solution into polyolefin porous thin film coating the surface and minute holes with living- polypropylene with terminal functional group. SOLUTION: Desirably 1-50wt.% of terminal denatured living-polymerization polypropylene is contained with polyolefin, that is, polypropylene, polyethylene and their composition, containing desirably not less than one wt.% of superhigh molecular weight component. After making this polyolefin composition to gelation form by adding solvent and heating dissolution, and forming polyolefin porous thin film through elongation and thermal immobilization, aprotic electrolytic thin film is formed. By coating the surface and the surface of the minute holes of polyolefin porous thin film with living-polymerization functional group, an electric cell with high conductivity and excellent durability is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aprotic electrolyte thin film and a method for producing the same, and more particularly, to an aprotic electrolyte thin film in which an aprotic electrolyte solution is immobilized on a polyolefin porous thin film and a method for producing the same.

[0002]

2. Description of the Related Art Electrolyte thin films are fields requiring low membrane resistance and excellent mechanical strength, such as fuel cells, salt electrolysis, primary batteries, secondary batteries, separation membranes for facilitated transport, electrochromic devices, and sensors. Widely available to. Among them, it can be used as a solid polymer electrolyte such as a lithium secondary battery.

A lithium secondary battery based on a polymer solid electrolyte prevents the formation of lithium metal dendrite to solve the problem of short-circuit damage and ignition of the battery, and has no liquid leakage as compared with a secondary battery based on a solution. In particular, development has been desired because it enables thinning and large area.

A polymer electrolyte in which a lithium salt such as LiClO ₄ is dissolved in a polyether such as polyethylene oxide or polypropylene oxide, a polyester, a polyimide or a polyether derivative has been developed, but the ionic conductivity is 10 ⁻⁵ to 10 ^{−. 3} s / cm is not exhibited unless the temperature is sufficiently higher than room temperature.

In order to reduce the effective resistance, as an example of thinning, a 0.1 μm or less solid polymer porous thin film of 0.1 μm or less is used.
A method for immobilizing a liquid ionic conductor by utilizing capillary condensation in fine pores having a size of μm or less (Japanese Patent Laid-Open No. 1-18055)
Although there is 1), the problem of the operating temperature has not been fundamentally solved.

Further, as a gel polymer in which a polymer matrix is impregnated with a salt and solvent solution similar to that of a conventional liquid type lithium battery, a technique using a cross-linked polyalkylene oxide as an electrolyte (USP 4,30)
3,748), and a technique (US Pat. No. 4,830,939) for gelling polyarylate and using it as an electrolyte has been proposed. Recently, a technique (USP 5,296,318) using a polymer gel obtained by impregnating a carbonate-based solution obtained by dissolving a lithium salt in a copolymer of polyvinylidene fluoride and hexafluoropropylene as an electrolyte has been proposed.
Although promising, there is a problem of oozing out of the electrolytic solution due to gel shrinkage at a high temperature, and there is a problem in solvent retention.

[0007]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems, is easy to form a thin film and has a large area, has excellent aprotic electrolyte solvent retention over a wide temperature range, and has a long-term stability. An object of the present invention is to provide an aprotic electrolyte thin film having improved properties and mechanical strength, and a method for producing the same.

[0008]

Means for Solving the Problems In view of the above problems, as a result of intensive studies, the present inventors have found that the main skeleton is composed of polyolefin having excellent solvent resistance and has an affinity for the electrolyte solvent used for the terminal chain. By impregnating the electrolyte solution into the polyolefin porous thin film whose surface and pore surface are coated with a polymer having a functional group, the aprotic electrolyte solution is immobilized on the membrane, and an aprotic electrolyte thin film having excellent solvent retention properties is obtained. The inventors have found that the present invention can be obtained, and reached the present invention.

[0009] That is, the aprotic electrolyte thin film of the present invention immobilizes an aprotic electrolyte solution on a polyolefin porous thin film into which a terminal-modified polypropylene has been introduced.

[0010] The method for producing an aprotic electrolyte thin film of the present invention comprises the steps of impregnating, coating or spraying a polyolefin porous thin film with living polymerized polypropylene whose terminal is modified with a functional group-containing monomer having an affinity for an aprotic solvent. And then immobilized by impregnation with an aprotic electrolyte solution.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The aprotic electrolyte thin film of the present invention has a main skeleton composed of a polyolefin porous thin film having excellent solvent resistance. This polyolefin porous thin film
A thin film containing a terminal-modified polymer having a functional group having an affinity for the solvent of the electrolyte solution used in the terminal chain, filled with an electrolyte solution in which the electrolyte is dissolved in the solvent, and stably held. Hereinafter, the present invention will be described in detail.

(1) Porous Polyolefin Thin Film The polyolefin porous thin film of the present invention is obtained by impregnating, coating or spraying a terminal modified polypropylene onto a polyolefin porous thin film.

1. Raw material a. Polyolefin composition Examples of the polyolefin having solvent resistance as a main skeleton include ethylene, propylene, 1-butene, and 4-methyl-.
A crystalline homopolymer or a copolymer obtained by polymerizing pentene-1, 1-hexene or the like may be mentioned. Among them, polypropylene and polyethylene (especially high-density polyethylene) are considered in consideration of the design of the porous structure and thinning. And their compositions are preferred.

The polyolefin has a weight average molecular weight of 5 × 10 ⁵ or more, preferably 1 × 10 ⁶ to 1 × 10 ^7.
Is preferably contained in an amount of 1% by weight or more, and the molecular weight distribution (weight average molecular weight / number average molecular weight) is 10 to 300. When the content of the ultrahigh molecular weight polyolefin component is less than 1% by weight, the portion which contributes to the improvement of the stretchability of the film is insufficient. On the other hand, the upper limit is not particularly limited. On the other hand, if the molecular weight distribution exceeds 300, breakage due to low molecular weight components occurs, and the strength of the entire thin film decreases, which is not preferable.

If the polyolefin has the above-mentioned molecular weight and molecular weight distribution, even if it is obtained by multi-stage polymerization,
The composition may be composed of two or more polyolefins.

The polyolefin containing an ultrahigh molecular weight component as described above may contain various additives such as an antioxidant, an ultraviolet absorber, an antiblocking agent, a pigment, a dye, and an inorganic filler, if necessary. It can be added within a range that does not impair the purpose of the present invention.

B. Terminal-modified polypropylene Terminal-modified polypropylene is a polypropylene having a functional group structure at the terminal. Here, as polypropylene,
Not limited to propylene homopolymer, propylene and other α-
One or more block copolymer rubbers with olefins (eg, ethylene, 1-butene, 1-hexene, 4-methyl-1-pentene, etc.) are included.

The polypropylene having a functional group structure at the terminal can be produced as follows. That is, it is produced by reacting a living polypropylene obtained by living polymerization of propylene with a functional group-containing monomer in the presence of a catalyst comprising a specific vanadium compound and an organoaluminum compound.

As the vanadium compound, V (acetylacetonato) ₃ , V (2-methyl-1,3-butanedionato) ₃ , and V (1,3-butanedionato) ₃ are preferred.
As the organic aluminum compound, 1 to 18 carbon atoms,
Preferably an organoaluminum compound having 2 to 6 carbon atoms or a mixture or complex compound thereof, for example,
Examples include dialkylaluminum monohalide, monoalkylaluminum dihalide, and alkylaluminum sesquihalide.

The polymerization reaction is inert to the polymerization reaction,
It is preferable to carry out the reaction in a solvent which is liquid at the time of polymerization. Such solvents include saturated aliphatic hydrocarbons, saturated alicyclic hydrocarbons, and aromatic hydrocarbons.

The amount of the polymerization catalyst used in the polymerization of propylene is 1 × 10 ^-4 per mole of propylene.
0.1 to 0.1 mol, preferably 5 × 10 ^{−4 to} 5 × 10 ⁻² mol, and the organoaluminum compound is 1 × 10 ^{−4 to} 0.5 mol, preferably 1 × 10 ^{−3 to} 0.1 mol. is there. In addition,
It is desirable to use 4 to 100 mol of the organoaluminum compound per 1 mol of the vanadium compound.

Living polymerization is usually carried out at a temperature between -100 ° C and 100 ° C.
C. for 0.5 to 50 hours. The molecular weight of the obtained living polypropylene can be adjusted by changing the reaction temperature and the reaction time. Lower the polymerization temperature, especially -30
By setting the temperature to not more than ° C, a polymer having a molecular weight distribution close to monodispersion can be obtained. Mw below -50 ° C
(Weight average molecular weight) / Mn (number average molecular weight) is 1.05
It can be a living polymer of from 1.40 to 1.40.

As described above, about 800 to 400,0
Living polypropylene having a number average molecular weight of 00 and close to monodispersion can be produced.

Next, in order to introduce a functional group structure into the terminal, living polypropylene is reacted with a functional group-containing monomer. As the monomers to be introduced, acrylic acid, methacrylic acid, acrylic acid ester, methacrylic acid ester, acrylamide, acrylonitrile, styrene and derivatives thereof are used. Specifically, for example, acrylates include methyl acrylate, ethyl acrylate, butyl acrylate, isobutyl acrylate,
2-ethylhexyl acrylate, lauryl acrylate, stearyl acrylate, ethyl decyl acrylate, ethyl hexadecyl acrylate, 2-ethoxyethyl acrylate, tetrahydrofurfuryl acrylate, trimethylolpropane triacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 1,4 butanediol diacrylate,
Acrylic monomers such as 1,6-hexanediol diacrylate are exemplified. Examples of methacrylates include methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, tridecyl methacrylate, stearyl methacrylate, and methacrylic acid. Examples include methacrylic monomers such as cyclohexyl acid, benzyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, glycidyl methacrylate, and ethylene glycol dimethacrylate. One or more of these can be selected and used. If necessary, a crosslinkable monomer such as vinyl acrylate, vinyl methacrylate, divinylbenzene, and vinyl butyl acrylate can be used.

Among the above-mentioned monomers, acrylic acid,
It is preferable to use a monomer composed of methacrylic acid or an ester thereof, or an acrylic monomer composed of acrylamide or a derivative thereof.

These monomers are appropriately selected depending on the solvent of the electrolytic solution used for producing the electrolyte thin film. In particular,
The selection is made in consideration of the Hansen parameter which is one of the solubility parameters indicating the solubility. The Hansen parameter refers to the solubility parameter as the effect of nonpolar interaction δ _d , the effect of polarization δ _p , the effect of hydrogen bonding δ
_h , three-dimensionally divided parameters into three components, the values of which are examined for many solvents (C.
M. Hansen, et al. , Encyclope
dia of Chemical Technology
y, N. Y. , P. 889, 1971). Also, when the Hansen parameters of a solvent having a high solubility (good solvent) and a poor solvent for a specific polymer are plotted on the three-dimensional spatial coordinates formed by δ _d , δ _p , and δ _h , the Hansen parameter of the good solvent becomes It has been empirically found to be located within a sphere of a certain size. That is, if the distance between a certain solvent and a polymer is close to the three-dimensional spatial coordinates (δ _d , δ _p , δ _h ), it can be regarded as a good solvent for the polymer.

In the present invention, the amount of a single monomer or a plurality of monomers forming a living polymer is adjusted in accordance with the Hansen parameter of the solvent of the electrolytic solution. This effectively swells and gels in the electrolytic solution,
It can be firmly fixed. Here, the polyolefin porous thin film into which the terminal-modified living polymer has been introduced selectively takes in an electrolyte solvent having an affinity for the living polymerization functional group covering the surface and the pore surface, but the main skeleton is resistant to the solvent. Since it is composed of polyethylene having excellent solvent properties, its swelling is appropriately suppressed as a whole, and large deformation and reduction in strength can be prevented.

The reaction between the living polypropylene and the functional group-containing monomer is carried out by supplying the monomer to a reaction system in which the living polypropylene exists. Reaction is usually -1
It is performed at a temperature of 00 ° C to 150 ° C for 5 minutes to 50 hours. By increasing the reaction temperature or lengthening the reaction time, it is possible to increase the modification ratio of the polypropylene terminal with the monomer unit. Usually, 1 to 1,000 mol of a monomer is used per 1 mol of living polypropylene.

The terminal-modified polypropylene obtained as described above has a number average molecular weight (Mn) of about 800 to 500,000, and has a very narrow molecular weight distribution (Mw / Mn) following the living polypropylene itself. =
1.05 to 1.40). In addition, the terminal has an average of 0.1 to 500, preferably 0.5 to 100 terminal structures of the monomers at the terminal. One feature of the end-modified polypropylene thus produced is that the syndiotactic dyad fraction is 0.6 or more.

2. Method for Producing Polyolefin Porous Thin Film In the method for producing a polyolefin porous thin film of the present invention, a solution is prepared by heating and dissolving the above-mentioned polyolefin composition in a solvent. Examples of the solvent include nonane, decane, decalin, p-xylene, undecane, dodecane,
An aliphatic or cyclic hydrocarbon such as liquid paraffin, or a mineral oil fraction having a boiling point corresponding thereto can be used.

The heat dissolution is carried out with stirring at a temperature at which the polyolefin composition is completely dissolved in the solvent, or by a method in which the polyolefin composition is uniformly mixed and dissolved in an extruder. In the case of dissolving with stirring in a solvent, the temperature varies depending on the polymer and the solvent to be used. For example, in the case of a polyethylene composition, the temperature is in the range of 140 to 250 ° C. When producing a porous thin film from a highly concentrated solution of a polyolefin composition, it is preferable to dissolve it in an extruder.

The mixing ratio of the polyolefin composition and the solvent is such that the total of the polyolefin composition and the solvent is 100% by weight.
The polyolefin composition is 10 to 50% by weight, preferably 10 to 40% by weight, and the solvent is 90 to 50% by weight, preferably 90 to 60% by weight. When the polyolefin composition is less than 10% by weight (when the solvent exceeds 90% by weight), when forming into a sheet, at the die exit,
The swell and neck-in are large, making the sheet formability and self-supporting difficult. On the other hand, when the polyolefin composition is 50
If the amount is more than 50% by weight (the amount of the solvent is less than 50% by weight), moldability decreases.

Next, the heated solution of the polyolefin composition thus melt-kneaded is extruded from a die or the like through an extruder and molded.

As the die, a sheet die having a rectangular die shape is usually used, but a double-cylindrical hollow fiber die, an inflation die and the like can also be used.
The die gap when using a sheet die is usually 0.1.
1-5mm, 140-250 ° C during extrusion
Heat to At this time, the extrusion speed is usually 20 to 30 cm
/ Min to 5 to 10 m / min.

The solution extruded from the die in this way is formed into a gel-like molded article by quenching.
Cooling is preferably performed at a rate of at least 50 ° C./min.

Next, this gel-like molded product is stretched. Stretching is performed by heating the gel-like molded product and at a predetermined magnification by a usual tenter method, roll method, inflation method, rolling method or a combination of these methods. The stretching may be uniaxial stretching or biaxial stretching, but biaxial stretching is preferred. In the case of biaxial stretching, either vertical or horizontal simultaneous stretching or sequential stretching may be used.

The stretching temperature is the melting point of polyolefin + 10 ° C.
Hereinafter, the reaction is preferably performed in a range from the crystal dispersion temperature of the polyolefin to less than the crystal melting point. For example, in the case of polyethylene, the temperature is in the range of 90 to 140C, preferably 100 to 130C.

Although the stretching ratio varies depending on the thickness of the raw material, it is preferably 2 times or more, more preferably 3 to 30 times in uniaxial stretching. In biaxial stretching, the area ratio is preferably 10 times or more, more preferably 15 to 400 times. If the area ratio is less than 10 times, stretching is insufficient and a highly elastic and high-strength microporous film cannot be obtained. On the other hand, if the area magnification exceeds 400 times, restrictions are imposed on the stretching operation and the like.

The stretched molded product is washed with a solvent to remove the remaining solvent. Examples of the washing solvent include hydrocarbons such as pentane, hexane, and heptane; chlorinated hydrocarbons such as methylene chloride and tetrachlorocarbon; fluorinated hydrocarbons such as ethane trifluoride; and ethers such as diethyl ether and dioxane. Volatile ones can be used. After the extraction, it is desirable to dry the washing solvent and heat-fix it in the temperature range from the crystal dispersion temperature to the melting point.

The polyolefin porous thin film produced as described above preferably has a breaking strength of 200 kg / cm ² or more. When the weight is 200 kg / cm ² or more, deformation resistance against swelling when the solvent of the electrolytic solution is dissolved in the living polymerization functional group becomes sufficient. Further, the thickness is preferably 0.1.
It is 1 to 100 μm, more preferably 0.2 to 50 μm. When the thickness is less than 0.1 μm, the mechanical strength of the film is small, and it is difficult to put the film to practical use. On the other hand, if it exceeds 100 μm, it is too thick, which is not preferable in producing small batteries and capacitors. The porosity and pore size are not particularly limited, but are preferably porosity and pore size within a range that does not impair ion conduction in a state where the electrolyte solution is introduced. Further, a porosity and a pore diameter in a range where an internal short circuit does not occur in the same state are preferable.

The obtained polyolefin porous thin film may be further subjected to a surface modification such as a plasma irradiation, a surfactant impregnation, a surface grafting or other hydrophilic treatment, if necessary.

3. Method for Introducing Terminal-Modified Polypropylene Terminal-modified polypropylene is dissolved in a solvent such as an aromatic hydrocarbon, a paraffinic hydrocarbon, chloroform, or tetrahydrofuran and introduced into a polyolefin porous thin film. As a method of introduction, the surface of the porous thin film and the surface of the pores can be coated by a method such as impregnation, application or spraying, and the solvent is dried after the introduction. The introduction amount is 1 to 50% by weight, preferably 3 to 50% by weight based on the polyolefin porous thin film.
30% by weight. At 1% by weight, impregnation of the solvent of the electrolyte solution,
The effect of immobilization cannot be expected. On the other hand, if it exceeds 50% by weight, the mechanical strength is significantly reduced.

(2) Electrolyte solution 1) Electrolyte As the electrolyte used in the present invention, an alkali metal salt or an alkaline earth metal salt is used. For example, LiF, NaI, L
iI, LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiB
F ₄ , LiCF ₃ SO ₃ , LiPF ₆ , NaSCN and the like.

2) Electrolyte Solvent The aprotic solvent for dissolving the electrolyte of the present invention includes:
Solvents stable to alkali metals, specifically, aprotic high dielectric constant solvents such as propylene carbonate, ethylene carbonate, γ-butyrolactone, dimethoxyethane, acetonitrile, formamide, tetrahydrofuran, and diethyl ether are used. You. As described above, the functional group of the terminal-modified polypropylene is selected so as to have an affinity for the solvent used in the present invention.

(3) Method for Producing Electrolyte Thin Film A method for preparing an aprotic electrolyte thin film by introducing an electrolyte solution in which an electrolyte is dissolved in an electrolyte solvent into a polyolefin porous film is performed by impregnating, coating or spraying the polyolefin thin film with an electrolyte solution. The methods can be used alone or in combination. Since the terminal functional group of the terminal-modified polypropylene has affinity for the aprotic solution, it can be easily impregnated and fixed in the polyolefin porous thin film. The introduction of the electrolyte solution may be performed before the battery is incorporated into the battery, during the assembly of the battery, or in the final step of assembling the battery.
Above all, since the conventional battery assembly process can be applied as it is, and the viewpoint of handleability during battery assembly, prevention of wrinkles and the like, adhesion to the positive and negative electrode plate surfaces, and the like, the electrolyte solution can be used during the battery assembly process or the final battery assembly process. Is preferred.

The battery obtained in this way uses the same electrolyte as the conventional aprotic liquid electrolyte. However, when the battery is introduced into a polyolefin thin film, the electrolyte is dissolved and swells in addition to fixation by capillary condensation. As a result, the liquid is not fixed, and as a result, there is no fear of liquid leakage, and the vapor pressure is remarkably reduced, making it difficult to burn. In addition, since the immobilized electrolytic solution works almost in the same way as the liquid state in ionic conductivity, the problem of operating temperature can be avoided.

[0047]

EXAMPLES The present invention will be described below in more detail with reference to examples, but the present invention is not particularly limited to the examples. In addition, the test method in an Example is as follows.

(1) Film thickness: The cross section was measured by a scanning electron microscope. (2) Porosity: measured by a gravimetric method. (3) Tensile breaking strength: measured according to ASTM D882.

Example 1 6% by weight of ultra high molecular weight polyethylene having a weight average molecular weight of 2.5 × 10 ⁶ , 24% by weight of high density polyethylene having a weight average molecular weight of 3.5 × 10 ⁵ , liquid paraffin (64 cst)
(/ 40 ° C) 0.375 parts by weight of an antioxidant per 100 parts by weight of the polyolefin composition was added to a 70% by weight mixture, and the mixture was heated and kneaded with a twin-screw extruder.

This was discharged from a die having a rectangular base, taken up by a chill roll adjusted to 30 ° C. and 0.5 m
m thick sheet. This sheet was simultaneously biaxially stretched 5 × 5 times at 115 ° C. using a batch-type biaxial stretching machine, and the remaining liquid paraffin was washed with n-hexane, dried at 120 ° C. while fixed to a metal frame, Heat set to 25μ thickness
m, porosity 43.5%, tensile strength at break 1049 kg /
A polyethylene porous thin film having a cm ² and an average pore diameter of 0.03 μm was obtained.

The porous polyethylene thin film obtained above was impregnated with a tetrahydrofuran solution containing 10% by weight of living polymerized polypropylene having a methyl acrylate group at a terminal having a weight average molecular weight of 50,000 for 1 hour, and then air-dried all day and night. The amount of living polymerized polypropylene introduced is 1
It was 4% by weight.

The obtained polyethylene porous thin film 10 × 10
0.1 cc of a γ-butyrolactone solution containing 1 mol% of LiBF ₄ at 25 ° C. was dropped into a square mm, and left in a closed container for 1 hour to obtain an aprotic electrolyte thin film. Immediately after removing the adhering liquid on the surface of the aprotic electrolyte thin film, the time-dependent change of the membrane weight was measured, and extrapolated after 0 seconds, the weight increase rate was 56%. In addition, the time-dependent change of the weight starting from the weight extrapolated after 0 seconds in the state of being left in the air at 25 ° C. was measured. As a result, the weight loss rate after 1 hour was 0.5% or less.

Further, this aprotic electrolyte thin film was punched out to a diameter of 10 mm, sandwiched between platinum black electrodes, and the electric resistance of the thin film was measured with an alternating current at a frequency of 1 KHz. When calculating the rate, 7 × 1
It was 0 ^-3 s / cm.

Comparative Example 1 A 10 × 10 mm square polyethylene microporous membrane obtained in the same manner as in Example 1 except that the terminal-modified polypropylene was not used was γ-butyrolactone containing 1 mol% of LiBF ₄ at 25 ° C. It was immersed in the solution for 1 hour to obtain an aprotic electrolyte thin film. Immediately after removing the adhering liquid on the surface of the aprotic electrolyte thin film, the time-dependent change of the membrane weight was measured, and the weight increase rate obtained by extrapolating after 0 second was 4%.
9%. In addition, a change with time in the weight starting from the weight extrapolated after 0 seconds in a state of being left in the air at 25 ° C. was measured. As a result, the weight reduction rate after 1 hour was 2.5%.

Further, this aprotic electrolyte thin film was punched out to a diameter of 10 mm, sandwiched between platinum black electrodes, and the electrical resistance of the thin film was measured with an alternating current of 1 KHz. When calculating the rate, 7 × 1
It was 0 ^-3 s / cm.

[0056]

The aprotic electrolyte thin film of the present invention uses a polyolefin porous thin film containing a living polypropylene having a functional group at a terminal. By suppressing the excessive swelling by the chain skeleton, the electrolyte solution can be stably held in a wide temperature range, and the evaporation rate of the electrolyte solution solvent can be kept extremely low. Further, by controlling the type and length of the functional group, the ionic conductivity can be easily controlled according to the purpose of use. That is, safety in overcharging can be improved without significantly lowering ionic conductivity.

In particular, when an ultrahigh molecular weight polyethylene component is used as the polyolefin, the aprotic electrolyte thin film has excellent mechanical strength and durability, and a primary battery, a secondary battery, a capacitor using an aprotic electrolyte, especially a lithium primary battery. It is suitably used for batteries and lithium secondary batteries.

Claims (6)

[Claims] An aprotic electrolyte thin film comprising an aprotic electrolyte solution immobilized on a polyolefin porous thin film into which a terminal-modified polypropylene has been introduced. 2. The aprotic electrolyte thin film according to claim 1, wherein the polyolefin porous thin film into which the terminal-modified polypropylene is introduced is a polyolefin porous thin film whose surface and pore surface are coated with the terminal-modified polypropylene. 3. The aprotic electrolyte thin film according to claim 1, wherein the terminal-modified polypropylene is a terminal functional group-modified polypropylene obtained by a living polymerization method. 4. The polyolefin composition according to claim 1, wherein the polyolefin contains at least 1% by weight of an ultrahigh molecular weight polyolefin, and the terminally modified polypropylene is 1 to 5% of the polyolefin.
4. The aprotic electrolyte thin film according to claim 1, which is 0% by weight. 5. An aprotic electrolyte characterized in that the surface and pore surface of a polyolefin porous thin film are coated with terminal-modified polypropylene, and the surface-coated polyolefin porous thin film is impregnated with an aprotic electrolyte solution and fixed. Manufacturing method of thin film. 6. A polyolefin composition wherein the polyolefin contains 1% by weight or more of an ultrahigh molecular weight polyolefin, and the terminal-modified polypropylene is a terminal functional group-modified polypropylene obtained by a living polymerization method, and 1 to 50% by weight of the polyolefin. A method for producing an aprotic electrolyte thin film according to claim 5.