JP3919346B2 - Polymer solid electrolyte thin film and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polymeric solid electrolytic thin film having high conductivity free from shortcircuiting due to dendrite. SOLUTION: This polymeric solid electrolytic thin film is formed to have thickness equal to or less than 20 μm and a real part impedance equal to or less than 8×103 Ω.cm2 at 10 kHz, and manufactured so that the porous part of a polyorefine fine porous film made of a polyorefine composition containing polyorefine of ultra polymeric molecular weight having average molecular weight equal to or above 5×105. The polymeric solid electrolytic film so manufactured can be made to have uniform thin film thickness equal to or less than 20 μm and the rear part impedance thereof has internal resistance as low as 8×103 Ω.cm2. Also, easy handling is ensured at the time of manufacture. Furthermore, the polyorefine porous phase works as a separator, thereby restraining the occurrence of dendrite and ensuring high safety.

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polymer solid electrolyte thin film, and more particularly to a polymer solid electrolyte thin film used for batteries, capacitors and the like.
[0002]
[Prior art]
The performance of mobile electronic devices such as mobile phones and personal digital assistants depends heavily on the rechargeable secondary batteries as well as the semiconductor elements and electronic circuits that are mounted. Realization is desired.
Up to now, lead batteries and nickel cadmium batteries have been used, but it has been difficult to cope with light weight and compactness due to insufficient energy density. Therefore, a nickel metal hydride battery having an energy density twice that of a nickel cadmium battery has been developed, and then a lithium ion battery having an energy density higher than that has been developed and has been in the limelight.
However, each battery uses a liquid electrolyte and is filled in a metal can in order to prevent liquid leakage, so that there is a limit to thickness and weight reduction.
[0003]
In view of this, polymer batteries in which a liquid electrolyte is made into a solid state are attracting attention. In particular, a crosslinked polymer is used as a gel polymer in which a polymer matrix is impregnated with a solution of a salt and a solvent similar to a conventional liquid type lithium battery. A technique using an alkylene oxide for an electrolyte (USP 4,303,748, etc.) and a technique for gelling polyacrylate and using it for an electrolyte (USP 4,830,939, etc.) have been proposed. Recently, a technology using a polymer gel in which a carbonate-based solution in which a lithium salt is dissolved in a copolymer of polyvinylidene fluoride and hexafluoropropylene as an electrolyte, and a copolymer of polyvinylidene fluoride and hexafluoropropylene are used. LiMn₂O_FourA technology (USP 5,296, 318, etc.) using a polymer gel impregnated with a carbonate-based solution in which a lithium salt is dissolved by mixing carbon black or petroleum coke and carbon black for a positive electrode or negative electrode of a battery has been proposed and is promising. However, there is a problem of electrolyte oozing due to gel contraction at a high temperature, which is not a complete solution for solvent retention.
[0004]
In order to lower the effective resistance, thinning is another solution, and the liquid ionic conductor is fixed using capillary condensation in a fine pore of 0.1 μm or less in a solid polymer porous thin film of 50 μm or less. However, the problem of the operating temperature cannot be fundamentally solved by this method alone (Japanese Patent Laid-Open No. 1-158051).
[0005]
[Problems to be solved by the invention]
An object of the present invention is to solve the above-described problems and to provide a thin polymer solid electrolyte membrane thin film having excellent conductivity without a dendrite short.
[0006]
[Means for Solving the Problems]
  As a result of diligent research to overcome the above-described prior art, the inventors of the present invention filled a polymer solid electrolyte into the pores in a specific polyolefin microporous membrane production process, and then performed a stretching operation to remove a polar solvent. It was found that a highly conductive polymer solid electrolyte thin film can be obtained by impregnation, and the present invention was completed.
  That is, the present inventionWeight average molecular weight 5 × 10 ⁵ After preparing a solution comprising 10 to 50% by weight of a polyolefin composition containing the above ultrahigh molecular weight polyolefin and 90 to 50% by weight of a solvent, the solution was extruded from a die, taken out by a cooling roll, and then a gel-like sheet was formed. After removing the residual solvent in the sheet and drying to produce a polyolefin microporous membrane, the polymer solid electrolyte was impregnated with a solution in which the polymer solid electrolyte was dissolved in a volatile solvent. After filling with volume% or more, the film is stretched by heating and then impregnated with a polar solvent. The thickness is 20 μm or less and the real part impedance at 10 KHz is 8 × 10 ³ Ω · cm ² Production method of polymer solid electrolyte thin film and weight average molecular weight 5 × 10 ⁵ After preparing a solution comprising 10 to 50% by weight of a polyolefin composition containing the above ultrahigh molecular weight polyolefin and 90 to 50% by weight of a solvent, the solution was extruded from a die, taken out by a cooling roll, and then a gel-like sheet was formed. Residual solvent in the sheet is removed and dried to produce a polyolefin microporous membrane, then impregnated with a solution in which a low molecular weight polymer electrolyte or electrolyte monomer is dissolved in a volatile solvent, and the low molecular weight polymer electrolyte or electrolyte monomer is porous After filling the pore part of the membrane with 5% by volume or more, heating and stretching, polymerizing to polymerize a low molecular weight polymer or monomer, and then impregnating with a polar solvent, the thickness is 20 μm or less, Real part impedance at 10 KHz is 8 × 10 ³ Ω · cm ² The following is a method for producing a polymer solid electrolyte thin film, a polymer solid electrolyte thin film produced by the production method, and a battery using the same.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
I. Polymer solid electrolyte thin film
The polymer solid electrolyte thin film of the present invention has a weight average molecular weight of 5 × 10^FiveThis is a low-resistance solid polymer electrolyte thin film which is a thin film in which a polymer solid electrolyte is contained in a polyolefin microporous membrane from a polyolefin composition containing the above ultrahigh molecular weight polyolefin. The configuration will be described below.
[0008]
1. Polyolefin microporous membrane
a. Polyolefin
Examples of the polyolefin include polyethylene, polypropylene, ethylene-propylene copolymer, polybutene-1, poly-4-methylpentene-1. Among these, polyethylene is preferable. As this polyethylene, those composed of ultrahigh molecular weight polyethylene, high density polyethylene, and medium and low density polyethylene can be used. From the viewpoint of strength, safety, film forming property, etc., the composition containing ultrahigh molecular weight polyethylene or its components It is preferable to use a product.
The polyolefin has a weight average molecular weight of 5 × 10^FiveOr more, preferably 1 × 10⁶~ 1x10⁷A polyolefin composition containing 1% by weight or more of the ultrahigh molecular weight component and having a molecular weight distribution (weight average molecular weight / number average molecular weight) of 10 to 300 is preferable. When the content of the ultrahigh molecular weight polyolefin component is less than 1% by weight, the portion contributing 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.
[0009]
b. Polyolefin microporous membrane
The polyolefin microporous membrane can be obtained by forming a polyolefin film. Film formation may be performed in accordance with the methods described in JP-A-60-242035 and JP-A-3-64334. For example, it can be performed as follows. After adding a polyolefin composition containing ultra-high molecular weight polyolefin at a ratio of 10 to 50% by weight with respect to the solvent and dissolving by heating to form a uniform solution, a sheet is formed from this solution and cooled to obtain a gel-like sheet It is obtained by heating and stretching to extract and remove the solvent, followed by drying and heat setting. The polymer solid electrolyte is added and filled before stretching in the above step. In addition, the polyolefin microporous film may contain various additives such as an antioxidant, an ultraviolet absorber, a lubricant, an antiblocking agent, a pigment, a dye, and an inorganic filler, as needed, without impairing the object of the present invention. Can be added.
[0010]
c. Properties of polyolefin microporous membrane
The polymer solid electrolyte thin film is obtained by filling a polymer solid electrolyte into a polyolefin microporous membrane matrix having the following physical properties.
The thickness of the polyolefin microporous membrane is 20 μm or less, preferably 0.1 to 20 μm, and the porosity is not limited, but is in the range of 30 to 95%, preferably 50 to 90%. The average pore diameter is preferably 1 μm or less, more preferably 0.001 to 1 μm, and the breaking strength is 200 kg / cm.²The above is preferable. When the polymer solid electrolyte thin film is used, if the thickness exceeds 20 μm, the effective resistance increases, the volume efficiency is disadvantageous, and the breaking strength is 200 kg / cm.²By setting it as the above, deformation resistance becomes enough. Moreover, when the porosity is less than 30%, the polymer solid electrolyte is insufficiently filled, and when the porosity exceeds 95%, the mechanical strength of the membrane is reduced and the practicality is inferior.
[0011]
2. Polymer solid electrolyte
As the polymer solid electrolyte filled in the polyolefin microporous membrane, a polar polymer such as polyether, polyester and polyimine, or a polymer of these polar polymer and nonpolar polymer, and an electrolyte such as alkali metal salt or proton acid are used. Complexes can be used. Further, it may be a single body that does not use an electrolyte.
As the electrolyte, an alkali metal salt or an alkaline earth metal salt is used, for example, LiF, NaI, LiI, LiClO._Four, LiAsF₆, LiPF₆, LiBF_Four, LiCF_ThreeSO_Three, NaSCN and the like.
[0012]
Specific examples of the polar polymer include polyether glycols such as polyethylene glycol, polyethylene glycol monoether, polyethylene glycol diether, polypropylene glycol, polypropylene glycol monoether, and polypropylene glycol diether, or a combination thereof. Polymer poly (oxyethylene oxypropylene) glycol, poly (oxyethylene oxypropylene) glycol monoether, or poly (oxyethylene oxypropylene) glycol diether, these polyoxyalkylenes and ethylenediamine Condensates can be used. Furthermore, there can be mentioned a copolymer of polyethylene glycol and dialkylsiloxane, a copolymer of polyethylene glycol and maleic anhydride, a copolymer of monomethyl ether of polyethylene glycol and methacrylic acid, and the like.
[0013]
The filling amount of the polymer solid electrolyte into the polyolefin microporous membrane is 5% by volume or more, preferably 30 to 70% by volume of the pores of the polyolefin microporous membrane. When the filling rate is less than 5% by volume, the interface with the electrolyte is reduced, and the application as a battery, a capacitor and an electrochromic element is not limited in terms of practicality, but the liquid retentivity of the polar solvent is reduced, Increased risk of leakage.
[0014]
3. Physical properties of polymer solid electrolyte thin films
The polymer solid electrolyte thin film has a thickness of 20 μm or less, preferably 5 to 20 μm. When the thickness exceeds 20 μm, the effective resistance increases and the volumetric efficiency is disadvantageous. The real part impedance at 10 KHz is 8 × 10^ThreeΩ · cm²Or less, preferably 0.5 × 10^ThreeΩ or less, and the specific conductivity is 10^-FiveScm^-1Or more, preferably 10^-3Scm^-1That's it. Real part impedance at 10 KHz is 8 × 10^ThreeΩ · cm²Exceeding this is not preferable because the internal resistance of the battery increases and the charge / discharge efficiency decreases.
In addition, the polymer solid electrolyte thin film of the present invention has a low roughness on the surface of the membrane, and when used as a battery, it has excellent adhesion to the electrode, an apparent surface area is increased, the battery capacity is improved, and a polyolefin fine particle is further improved. Since the matrix of the porous membrane is filled with the polymer solid electrolyte, there is a feature that there is no leakage and short-circuiting due to dendrites can be suppressed.
[0015]
II. Method for producing polymer solid electrolyte thin film
The polymer solid electrolyte thin film of the present invention is obtained by obtaining a gel-like sheet at the time of producing a polyolefin microporous film as described above, filling the electrolyte, stretching, and impregnation with a polar solvent. As a method of filling the polymer electrolyte, there are a method of directly filling a polymer solid electrolyte into a minute and high film and a method of filling a low molecular weight polymer electrolyte or a monomer electrolyte and increasing the molecular weight after film formation. These methods will be described below.
[0016]
1. Method for filling a polymer solid electrolyte into a polyolefin microporous membrane
In the method for producing a polyolefin microporous membrane of the present invention, a solution is prepared by heating and dissolving the above-described polyolefin composition in a solvent. Examples of the solvent include aliphatic or cyclic hydrocarbons such as nonane, decane, decalin, p-xylene, undecane, dodecane, and liquid paraffin, or mineral oil fractions having boiling points corresponding to these. The viscosity of this solvent is preferably 30 to 500 cSt, particularly 50 to 200 cSt at 25 ° C. When the viscosity at 25 ° C. is less than 30 cSt, non-uniform discharge occurs and kneading is difficult.
[0017]
The dissolution by heating is performed with stirring at a temperature at which the polyolefin composition is completely dissolved in a solvent, or by uniformly mixing and dissolving in an extruder. In the case of dissolving in a solvent while stirring, the temperature varies depending on the polymer and the solvent to be used. When producing a microporous membrane from a high concentration solution of a polyolefin composition, it is preferable to dissolve in a extruder. When melt | dissolving in an extruder, the polyolefin composition mentioned above is first supplied to an extruder, and it melts. Although melting temperature changes with kinds of polyolefin to be used, melting | fusing point of polyolefin + 30-100 degreeC is preferable. For example, in the case of polyethylene, it is preferably 160 to 230 ° C., particularly 170 to 200 ° C., and in the case of polypropylene, it is preferably 190 to 270 ° C., particularly preferably 190 to 250 ° C. Next, a liquid solvent is supplied from the middle of the extruder to the molten polyolefin composition.
[0018]
The blending ratio of the polyolefin composition and the solvent is 10 to 50% by weight of the polyolefin composition and 90 to 50% by weight of the solvent, where the total of the polyolefin composition and the solvent is 100% by weight. When the polyolefin composition is less than 10% by weight (when the solvent exceeds 90% by weight), when forming into a sheet, swell and neck-in are large at the die exit, making it difficult to form and self-support the sheet. . On the other hand, when the polyolefin composition exceeds 50% by weight (if the solvent is less than 50% by weight), shrinkage in the thickness direction increases, the porosity decreases, and the moldability also decreases. By changing the concentration within this range, the permeability of the membrane can be controlled.
Next, the heated solution of the polyolefin composition melt-kneaded in this way is extruded from a die or the like and molded. As the die, a sheet die having a rectangular base shape is usually used, but a double cylindrical hollow fiber die, an inflation die, or the like can also be used. When a sheet die is used, the die gap is usually 0.1 to 5 mm. At the time of extrusion molding, it is heated to 140 to 250 ° C. and extruded.
[0019]
The solution extruded from the die is formed into a gel-like sheet by being taken up by a cooling roll, and the pore diameter and the like can be controlled by controlling this cooling condition. The take-up speed is 1 to 20 m / min, preferably 3 to 10 m / min. The gel-like molded product obtained by passing through a cooling roll is washed with a solvent to remove the remaining solvent. Cleaning solvents include hydrocarbons such as pentane, hexane and heptane, chlorinated hydrocarbons such as methylene chloride and tetrasalt carbon, fluorinated hydrocarbons such as ethane trifluoride, and ethers such as diethyl ether and dioxane. Volatile ones can be used. These solvents are appropriately selected according to the solvent used for dissolving the polyolefin composition, and used alone or in combination. The cleaning method can be performed by a method of immersing and extracting in a solvent, a method of showering a solvent, or a method using a combination thereof. Washing as described above is performed until the residual solvent in the molded product is less than 1% by weight. Thereafter, the cleaning solvent is dried. The cleaning solvent can be dried by heat drying, air drying, or the like. The dried molded product is preferably heat-set in the temperature range of the crystal dispersion temperature to the melting point.
[0020]
The polymer solid electrolyte is filled by immersing the polyolefin microporous film subjected to the solvent removal treatment in a diluted solution of the polymer solid electrolyte. Moreover, even in the case of an untreated gel-like sheet that has not been subjected to solvent removal treatment, it can be filled by press-fitting a diluted solution of a polymer solid electrolyte. However, it is more preferable to immerse the polyolefin microporous membrane in the presence of a volatile solvent after the solvent removal treatment because it can be filled more easily.
[0021]
The dilution concentration of the polymer solid electrolyte diluted solution varies depending on the amount of the polymer solid electrolyte filled in the polyolefin microporous membrane, but is preferably at least 0.05% by weight, particularly preferably 0.5% by weight or more. If the concentration is less than 0.05% by weight, the polymer solid electrolyte filled in the polyolefin microporous membrane is insufficient, and pinholes are likely to occur during stretching. The solution viscosity is preferably less than 500 cSt at 25 ° C., particularly preferably less than 100 cSt, in order to uniformly fill the entire polyolefin microporous membrane.
The filling amount of the polymer solid electrolyte in the polyolefin microporous membrane is preferably 5% by volume or more, more preferably 30 to 70% by volume. When the filling rate is less than 5% by volume, the interface with the electrolyte is reduced, and the application as a battery, a capacitor and an electrochromic element is not limited in terms of practicality, but the liquid retentivity of the polar solvent is reduced, Increased risk of leakage.
[0022]
Next, the obtained polymer solid electrolyte-containing polyolefin microporous membrane is stretched. The stretching method is performed at a predetermined magnification by heating at a temperature not higher than the melting point of the polyolefin + 10 ° C. and using a normal 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 longitudinal or transverse simultaneous stretching or sequential stretching may be used. The draw ratio varies depending on the thickness of the original fabric, but is stretched so that the thickness of the polymer solid electrolyte thin film is 1.5 μm or more and 20 μm or less. Thereafter, the volatile solvent is appropriately dried. For example, vacuum drying is performed at 50 to 80 ° C. for 3 to 5 minutes, and heat setting is performed as necessary.
[0023]
Next, the polymer solid electrolyte-containing film obtained above is impregnated with a polar solvent. Examples of polar solvents to be impregnated include propylene carbonate, ethylene carbonate, γ-butyrolactone, methyl furan, dimethoxyethane, dioxolane, tetrahydrofuran, acetonitrile, dimethylformamide, dimethyl sulfoxide, methyl tetrahydrofuran, sulfolane, methyl thiophene, methyl thiazole, ethoxymethoxy Ethane and the like can be mentioned, and one or more of these solvents may be used. Further, the above electrolyte may be added to this polar solvent. At this time, the polymer solid electrolyte may be gelled by impregnating with a polar solvent. The polymer solid electrolyte thin film is obtained by impregnating with a polar solvent as described above.
[0024]
2. A method of filling a polymer solid electrolyte in the pores of a polyolefin microporous membrane by a polymerization method
In the production of the above-mentioned polymer solid electrolyte-filled polyolefin microporous membrane, after removing the solvent in the gel sheet, a solution of a low molecular weight polymer electrolyte is filled instead of the polymer solid electrolyte, or the raw material for the polar polymer is used. Fill with electrolyte monomer solution. Specific examples of the low molecular weight polymer electrolyte include oligomers of the above polar polymers and low molecular weight polymers. Specific examples of the monomer include aniline, acrylonitrile, pyrrole, styrene, propylene glycol, ethylene oxide, propylene. Examples thereof include oxides and vinyl compounds. These solutions may be a complex solution in which an electrolyte such as an alkali metal salt or a proton acid is mixed. The filling method is performed by immersing the polyolefin microporous membrane in the presence of a volatile solvent in the same manner as the filling of the solid polymer electrolyte.
The amount of the low molecular weight polymer electrolyte or electrolyte monomer filled in the polyolefin microporous membrane is filled to 5% by volume or more in the pores of the polyolefin microporous membrane when polymerized in a subsequent step to obtain a high molecular weight solid electrolyte. And it is preferable to fill 30 to 70% by volume of the pore volume.
[0025]
Next, the polyolefin microporous film containing the obtained low molecular weight polymer electrolyte or electrolyte monomer solution is stretched. The stretching method is carried out at a predetermined magnification by heating at a temperature below the melting point of the polyolefin of −10 ° C. and 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 longitudinal or transverse simultaneous stretching or sequential stretching may be used. Although the draw ratio varies depending on the thickness of the original fabric, it is stretched so that the thickness of the electrolyte-containing polyolefin microporous film is 1.5 μm or less when it is 1.5 times or more. The solvent contained in the stretched film is subjected to reduced pressure or natural drying, followed by post-polymerization.
[0026]
As the polymerization method, a method of heating a low molecular weight polymer electrolyte or an electrolyte monomer-containing polyolefin microporous membrane, or a method of irradiating radiation such as ultraviolet rays, plasma, electron beams, γ rays, or the like can be used. The low molecular weight polymer or monomer filled in the pores is polymerized to have a high molecular weight, thereby forming a polymer solid electrolyte-containing polyolefin microporous film.
As a specific example of plasma irradiation, 10^-2Plasma treatment for 1 to 1000 seconds at an ordinary frequency of 10 to 30 MHz and an output of 1 to 1000 W is performed on an electrolyte-containing polyolefin microporous membrane in the presence of a gas such as argon, helium, nitrogen, air or the like at a pressure of 10 mbar. . Moreover, as an electron beam irradiation polymerization method, the said electrolyte-containing polyolefin microporous film is irradiated with an electron beam at an acceleration voltage of 100 to 5000 KeV, more preferably 200 to 800 KeV. As an irradiation amount, 10-500KGy is suitable, Preferably it is 50-200KGy.
[0027]
Next, the polymer solid electrolyte-containing polyolefin microporous membrane obtained above is impregnated with a polar solvent. Examples of polar solvents to be impregnated include propylene carbonate, ethylene carbonate, γ-butyrolactone, methyl furan, dimethoxyethane, dioxolane, tetrahydrofuran, acetonitrile, dimethylformamide, dimethyl sulfoxide, methyl tetrahydrofuran, sulfolane, methyl thiophene, methyl thiazole, ethoxymethoxy Ethane and the like can be mentioned, and one or more of these solvents may be used. Further, the above electrolyte may be added to this polar solvent. At this time, the polymer solid electrolyte may be gelled by impregnation with a polar solvent. The polymer solid electrolyte thin film is obtained by impregnating with a polar solvent as described above.
[0028]
III. battery
Applications of the polymer solid electrolyte thin film obtained above include primary batteries, secondary batteries, electrochromic devices, large-capacity capacitors, sensors, and the like.
Particularly useful as a polymer battery. As a polymer battery, a polymer battery having high voltage, high capacity, high efficiency, no leakage, high safety, and excellent in economic efficiency as compared with a battery using a conventional liquid electrolyte can be obtained.
That is, applying this polymer solid electrolyte thin film, utilizing a composite electrode that is lightweight and excellent in flexibility, the porous polymer substrate skeleton made of polyolefin is used to suppress excessive swelling of the filled polymer solid electrolyte, Good conductivity can be maintained stably over a wide temperature range over a wide temperature range. That is, it is possible to manufacture a polymer battery that can improve safety in overcharging without significantly reducing electronic conductivity, and discharge at a higher rate than conventional polymer electrolyte lithium batteries is possible. .
[0029]
【Example】
The present invention will be described in more detail with reference to the following specific examples, but the present invention is not particularly limited to the examples. In addition, the test method in an Example is as follows.
(1) Impedance: The impedance (R) of the real part was measured at 10 KHz using a Solartron impedance measuring device.
(2) Dendrite: A load of 5 kgf was applied to the electrode, 1000 cycles were performed with 3-4 V cyclic voltammetry, and a short circuit was confirmed.
(3) Roughness of film: An average roughness (Ra) was measured using a stylus type step gauge.
(4) Discharge capacity: Calculated from the time from 4.2 V to 3.0 V in 1.0 c discharge.
[0030]
  Example 1
  Weight average molecular weight 2.5 × 10⁶4% by weight of ultra high molecular weight polyethylene, weight average molecular weight 3.3 × 10⁵16% by weight of high-density polyethylene and 80% by weight of liquid paraffin were melt-kneaded with a twin-screw extruder, extruded from a T-die installed at the tip, and cooled to form a 75 μm gel sheet. The obtained sheet was washed with methylene chloride to remove the solvent, and then heat fixed at 120 ° C. to obtain a polyethylene microporous membrane. The obtained polyethylene microporous membrane was mixed with a 1 mol methylene chloride solution of polyethylene glycol having an average molecular weight of 4000 and LiClO.₄Of 0.2 molar methylene chloride. Next, it was naturally dried under an argon atmosphere for 10 minutes to remove methylene chloride, and further dried in an oven at 80 ° C. under an argon atmosphere for 10 minutes. The obtained sheet was filled with 9.6% by volume of polyethylene glycol. Obtained filling sheetTheThe film was drawn MD / TD = 3/3 times at 115 ° C. with a batch type biaxial drawing machine to obtain a thin film having a thickness of 11 μm. To this thin film, 1 mol LiClO of propylene carbonate: dimethoxyethane (DME) = 1: 1₄The polymer solid electrolyte thin film was obtained by impregnating the solution. The impedance of the obtained polymer solid electrolyte thin film was 4.1 × 10³Ω · cm²The film roughness was 5 μm or less. Further, dendrites were measured by sandwiching a polymer solid electrolyte thin film with a 16φ Au electrode, but no short circuit due to dendrites was observed.
[0031]
Next, using the polymer solid electrolyte thin film obtained above, 16φ LiCoO₂Was used as a positive electrode and metal Li was used as a negative electrode. When the discharge capacity by 10 cycles was measured with this battery, it was 520 mAh / g.
[0032]
Example 2
Weight average molecular weight 2.5 × 10⁶4% by weight of ultra high molecular weight polyethylene, weight average molecular weight 3.3 × 10^Five16% by weight of high-density polyethylene and 80% by weight of liquid paraffin were melt-kneaded with a twin screw extruder, extruded from a T-die installed at the tip, and cooled to form a 30 μm gel sheet. The obtained sheet was washed with methylene chloride to remove the solvent, and heat fixed at 120 ° C. to obtain a polyethylene microporous membrane. The obtained polyethylene microporous membrane was impregnated with a 0.1 molar methylene chloride solution of polyethylene glycol having an average molecular weight of 300. Next, it was naturally dried under an argon atmosphere for 10 minutes to remove methylene chloride, and further dried in an oven at 80 ° C. under an argon atmosphere for 10 minutes. The obtained sheet was stretched by MD / TD = 1.5 / 1.5 times at 115 ° C. with a batch type biaxial stretching machine to obtain a low molecular weight polymer electrolyte thin film having a thickness of 17 μm. Next, the low molecular weight polymer electrolyte thin film was irradiated with a gamma dose of 1.5 MRad for 1 minute to increase the molecular weight of the low molecular weight polymer. The resulting sheet was filled with 18% by volume of high molecular weight polyethylene glycol. Thereafter, 1 mol LiClO dissolved in a propylene carbonate: DME = 1: 1 solution in an argon atmosphere._FourWas further impregnated. When the properties of the obtained polymer solid electrolyte thin film were measured in the same manner as in Example 1, the real part impedance of the obtained polymer solid electrolyte thin film was 6.8 × 10 6.^ThreeΩ · cm²The roughness of the film was 5 μm or less, and no short circuit due to dendrite was observed.
[0033]
Comparative Example 1
A 0.1 molar methylene chloride solution of polyethylene glycol having an average molecular weight of 4000 and LiClO on a 16φ Au electrode._FourWas mixed with a 1 mol methylene chloride solution with a Teflon spatula and dried at 80 ° C. for 10 minutes. This operation was repeated three times to obtain a 54 μm electrolyte membrane on the Au electrode, and the properties were measured in the same manner as in Example 1. As a result, the impedance was 5.1 × 10 5.^FiveΩ · cm²The roughness of the film was 10 μm or less, and no short circuit due to dendrite was observed.
[0034]
Comparative Example 2
16φ LiCoO₂On the electrode, a 0.1 molar methylene chloride solution of polyethylene glycol having an average molecular weight of 4000 and LiClO._FourA mixture of 1 mol of methylene chloride with a teflon spatula and dried at 80 ° C. for 10 minutes, LiCoO₂An electrolyte membrane of 18 μm was obtained on the electrode, and 16φ LiCoO was obtained in the same manner as in Example 2.₂Was used as the positive electrode and Li as the negative electrode. When the discharge capacity by 10 cycles was measured with this battery, it was 320 mAh / g.
[0035]
Comparative Example 3
Weight average molecular weight 2.5 × 10⁶4% by weight of ultra high molecular weight polyethylene, weight average molecular weight 3.3 × 10^Five16% by weight of high-density polyethylene and 80% by weight of liquid paraffin were melt-kneaded with a twin screw extruder, extruded from a T-die installed at the tip, and cooled to form a 400 μm gel sheet. The obtained sheet was stretched by MD / TD = 5/5 times at 115 ° C. with a continuous biaxial stretching machine to obtain a film having a thickness of 15 μm. The obtained film was washed with methylene chloride to remove the solvent, and heat fixed at 120 ° C. to obtain a polyethylene microporous film.
The obtained polyethylene microporous membrane was mixed with a 0.1 molar methylene chloride solution of polyethylene glycol having an average molecular weight of 4000 and LiClO._FourOf 1 mol of methylene chloride was impregnated. Subsequently, it was naturally dried for 10 minutes in an argon atmosphere to remove methylene chloride, and further dried in an oven at 80 ° C. in an argon atmosphere for 10 minutes to obtain a polymer solid electrolyte thin film having a thickness of 15 μm. When the properties were measured in the same manner as in Example 1, the real part impedance was 2.0 × 10^FourΩ · cm²The roughness of the film was 15 μm or more, and no short circuit due to dendrite was observed.
[0036]
【The invention's effect】
Since the solid polymer electrolyte membrane of the present invention can be uniformly formed into a thin film of 20 μm or less, the real part impedance is 8 × 10 8.^ThreeΩ · cm²The internal resistance is low and the handling is good during manufacturing. In addition, since the polyolefin porous phase serves as a separator, it is a solid electrolyte membrane that suppresses the generation of dendrites and is highly safe. Therefore, when a battery is produced using the polymer solid electrolyte membrane of the present invention, a battery having a high capacity and high productivity and high safety can be obtained.

Claims (4)

A solution comprising 10 to 50% by weight of a polyolefin composition containing an ultra-high molecular weight polyolefin having a weight average molecular weight of 5 × 10 ⁵ or more and a solvent of 90 to 50% by weight is prepared. The solution is extruded from a die and taken up by a cooling roll. After forming the gel sheet, the residual solvent in the sheet is removed, dried to produce a polyolefin microporous membrane, and then impregnated with a solution in which the polymer solid electrolyte is dissolved in a volatile solvent, so that the polymer solid electrolyte is porous. The pore portion of the membrane is filled with 5% by volume or more, then stretched by heating, and then impregnated with a polar solvent. The thickness is 20 μm or less, and the real part impedance at 10 KHz is 8 × 10 ³ Ω. -The manufacturing method of the polymer solid electrolyte membrane which is cm < ² > or less . A solution comprising 10 to 50% by weight of a polyolefin composition containing an ultra-high molecular weight polyolefin having a weight average molecular weight of 5 × 10 ⁵ or more and a solvent of 90 to 50% by weight is prepared. The solution is extruded from a die and taken up by a cooling roll. After forming the gel sheet, the residual solvent in the sheet is removed and dried to produce a polyolefin microporous membrane, which is then impregnated with a solution in which a low molecular weight polymer electrolyte or electrolyte monomer is dissolved in a volatile solvent, and then a low molecular weight polymer. It is characterized by filling the pore portion of the porous membrane with 5% by volume or more of an electrolyte or electrolyte monomer, then heating and stretching, polymerizing to polymerize a low molecular weight polymer or monomer, and then impregnating with a polar solvent. thickness at 20μm or less, a polymer solid electrolyte real part impedance is 8 × 10 ³ Ω · cm ² or less at 10KHz Method of manufacturing the film. A polymer solid electrolyte thin film produced by the method for producing a polymer solid electrolyte thin film according to claim 1. A battery using the solid polymer electrolyte thin film according to claim 3 .