JP2001118603A - Porous sheet for forming polymer gel, polymer gel electrolyte using the same, and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a porous sheet capable of forming a polymer gel electrolyte having high ionic conductivity by swelling and / or gelling with an electrolyte, a polymer gel electrolyte using the same, and Provided is a method for producing the gel electrolyte. SOLUTION: This is a fibrous sheet composed of at least two or more kinds of fibrous materials of an acrylonitrile polymer, and when the fibrous sheet is immersed vertically with respect to the liquid surface of diethyl carbonate, A porous sheet material for forming a polymer gel electrolyte, which is a fibrous sheet having a function of sucking an electrolyte up to 1.5 mm / min or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a porous sheet for forming a polymer gel electrolyte used for various electric devices such as a lithium battery, a lithium ion secondary battery, and an electric double layer capacitor. More specifically, a porous sheet capable of forming a polymer gel electrolyte exhibiting high ionic conductivity by swelling and / or gelling with an electrolytic solution, a polymer gel electrolyte using the same, and a method for producing the gel electrolyte It is about.

[0002]

_2. Description of the Related Art LiCoO ₂ , LiMnO ₂ , LiNi
A lithium composite oxide such as O ₂ is used as a positive electrode active material,
i metal, Li alloy, or a carbon material having the ability to insert and extract Li is used as a negative electrode or a negative electrode active material, and LiBF ₄ ,
Lithium ion batteries using an organic solvent in which an electrolyte salt such as LiClO ₄ or LiPF ₆ is dissolved as an electrolyte have a high energy density and excellent cycle characteristics, and are therefore used in personal computers, mobile phones, mini components, mini disks, etc. Has been greatly developed as a power supply for electronic devices.

However, lithium ion batteries that have been conventionally developed use an organic solvent such as ethylene carbonate or propylene carbonate as an electrolytic solution, so that the batteries suffer from inconveniences such as internal short-circuits and external short-circuits, and the battery temperature is reduced. When it rises, there is a problem that the electrolyte volatilizes and the battery explodes or a fire occurs.

In order to avoid such danger, a microporous polyolefin film is used as a separator between the positive and negative electrodes. However, the current separator has a porosity of 2
It is known that the ion conductivity of the combination of the separator and the electrolytic solution is extremely lower than that of the system using only the electrolytic solution because the portion other than the micropores of the separator does not contribute to ionic conduction. ing. Furthermore, since the polyolefin-based material does not swell with respect to the electrolytic solution, there is a problem that even if the battery is exposed to a high-temperature atmosphere, the separator cannot solidify the electrolyte and thus cannot prevent liquid leakage.

[0005] A method of impregnating and holding an electrolytic solution in a nonwoven fabric of polyolefin-based fibers is also known.
Since the thickness is as large as 00 μm or more and the distance between the electrodes is large, it is not preferable for a lithium battery in which the reduction of internal resistance is a problem. Also, if a thin nonwoven fabric is used, the denseness in the thickness direction is insufficient, so that a soft short between the electrodes is easy. There is a problem that occurs.

Japanese Patent Application Laid-Open No. Hei 7-32081 discloses a method in which a vinyl polymer is dissolved, a solution obtained by adding LiClO ₄ to this solution is cast, and propylene carbonate is added to a film obtained by evaporating the solvent to form a solid electrolyte. It is impregnated at room temperature so that the weight ratio of propylene carbonate to film becomes 4: 1 to form a gel electrolyte,
Since the impregnating property of the film with propylene carbonate is not very good and the obtained gel structure does not have good electrolyte retention, the battery using the gel electrolyte also has a problem that liquid leakage easily occurs.

JP-A-10-144137 discloses a method for obtaining a sheet-like gel electrolyte by adding an electrolytic solution to a sheet made of acrylonitrile-based short fibers and cooling the sheet to a room temperature or lower without heating. However, there is a problem that this gel electrolyte has poor heat resistance and becomes fluid immediately upon heating.

In general, a casting method in which a polymer solid electrolyte or a gel electrolyte is cast from a solution in which a polymer is dissolved, a solvent is removed to form a film, and then a non-aqueous electrolyte is impregnated. However, the electrolyte prepared by the casting method has a problem of a residual solvent, and is not suitable for applications requiring electrochemical stability. Furthermore, in the case of a film, there is a problem that the electrolyte absorbency of the electrolyte is low, and the electrolyte does not spread evenly to form a gel electrolyte having spots of dissolution.

Also, if the polymer constituting the electrolyte sheet has high solubility, the gel sheet softens at high temperature and the mechanical strength becomes weak. On the other hand, the sheet made of the polymer having low solubility has the problem that an electrolyte containing a low viscosity solvent contains There is a problem that the liquid absorbing property of the liquid is poor and the ion conductivity of the gel electrolyte is lowered at a low temperature. This is described in Japanese Patent Application Laid-Open No. 10-2613.
As shown in Japanese Patent Publication No. 15, an electrolytic solution is added to a mixture of powders of two or more acrylonitrile copolymers having at least one of a copolymerization component and a copolymerization ratio different from each other, cast, heated, and cooled. However, the resulting gel electrolyte sheet has tackiness based on its viscoelasticity, its handleability is poor, there is a difficulty in handling in the battery assembly process, and it is stretched. It is still insufficient as a gel electrolyte for producing a battery provided with an electrolyte layer having uniform characteristics.

[0010]

SUMMARY OF THE INVENTION The inventors of the present invention have a high ionic conductivity that can solve the above-mentioned problems of the prior art, and have a sufficient density in the thickness direction of the electrolyte sheet. The present invention was completed as a result of studying to obtain an electrolyte sheet which could prevent short-circuiting and to obtain a polymer gel electrolyte-forming fibrous sheet having excellent electrolyte absorption and good productivity.

[0011]

SUMMARY OF THE INVENTION The present inventors have developed a gel-forming polymer soluble in an organic solvent, a swellable fibrous material, or a gel-forming polymer soluble in an organic solvent. It has been found that the above-mentioned problems can be solved by using a polymer sheet having a porous structure, which is a sheet-like material comprising a combination of a fibrous material of the above and a fibrous material of a polymer which swells in an organic solvent. The gist is a fibrous sheet composed of at least two or more acrylonitrile-based polymer fibrous materials, and when the sheet is vertically immersed in diethyl carbonate, A porous sheet material for forming a polymer gel electrolyte, which has a function of sucking an electrolytic solution at 1.5 mm / min or more, a polymer gel electrolyte using the same, and the porous sheet material Impregnated with a non-aqueous electrolyte solution, 50
This is a method for producing a polymer solid electrolyte obtained by heating at 75 ° C. for 1 to 20 minutes and cooling and holding at room temperature for 6 to 12 hours to gel or swell.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in more detail.

The porous sheet material in the present invention is composed of at least two or more kinds of acrylonitrile polymer fibrous materials, and is a fibrous sheet which is immersed perpendicularly to the liquid surface of diethyl carbonate. sometimes,
Electrolyte can be sucked up at 1.5 mm / min or more.

It is desirable that the porous sheet, which is a material constituting the gel electrolyte, has a high electrolyte absorbing property. In the gel electrolyte of the present invention, the soluble polymer constituting the fibrous sheet is once dissolved in an electrolytic solution by heating and then cooled to form a gel. Therefore, if the electrolytic solution has a low liquid absorbing property, the electrolytic solution may not be evenly distributed in the sheet, which may cause dissolution spots. Further, the dissolution spots are also a cause of lowering the ionic conductivity of the obtained solid electrolyte, which is not preferable. When the fibrous sheet of the present invention is impregnated with a non-aqueous electrolyte, the non-aqueous electrolyte can be used in a very short time by utilizing the capillary phenomenon of the fibrous sheet of the present invention. Uniformly penetrate between the fibers constituting

The porosity of the porous sheet of the present invention is preferably 40 to 60%. The porosity in the sheet is necessary to maintain high ionic conductivity when the gel electrolyte is used, and the porosity is used as a measure thereof. The porosity referred to here is a volume fraction of voids in the sheet, calculated from a formula of porosity = (pore volume / sheet volume) × 100. If the porosity of the sheet is less than 40%, the permeability of the electrolyte is low, the electrolyte does not sufficiently reach the inside of the sheet, and it is difficult to produce a polymer gel having high ionic conductivity. On the other hand, if the porosity exceeds 60%, the density in the thickness direction of the sheet becomes low, which causes a soft short circuit of the solid electrolyte, which is not preferable.

The porous sheet of the present invention has a thickness of 50
It is preferably at most 30 μm, more preferably at most 30 μm. If the thickness of the sheet exceeds 50 μm, the internal resistance of the polymer gel electrolyte using the sheet increases, which is not preferable.

The fibrous polymer constituting the sheet of the present invention may be prepared by melt spinning, wet spinning, dry spinning, or sea-island fiber forming by composite spinning.
A short fibrous material having a diameter of preferably 1 to 20 μm, obtained by spinning by a split fiber forming method or the like, or a flash spinning method or a solution of a high-molecular polymer, and a high flow rate of a liquid or gas having a coagulating force. A pulp-like material produced by discharging into a turbulent liquid flow and solidifying under a shear flow is preferable. At this time, a fibrous substance or a pulp-like substance can be formed by a composite spinning method or a mixed spinning method using two or more kinds of polymers to be used.

In the case of the above short fibers, the diameter of the fibers is from 1 to 20.
μm and a length of 2 to 5 mm are desirable. It has a diameter of 2
If the fiber diameter exceeds 0 μm and the fiber diameter is too large, it is difficult to produce a thin and uniform sheet, and a fiber length exceeding 5 mm also causes sheet unevenness, which is not preferable.
On the other hand, fibers having a diameter of less than 1 μm make spinning difficult and have low productivity, and a porous sheet made using fibers having a fiber length of less than 2 mm is not preferred because the strength of the sheet is reduced.

The pulp-like material has a structure in which fibrils having a diameter of several μm or less are branched from a fibrous trunk, and a sheet-like material made from this pulp-like material is efficiently entangled with fibers. Even if it is a thin sheet-shaped material, it has the characteristics that it is excellent in handleability and excellent in impregnation characteristics of a non-aqueous electrolyte due to its unique structure.

The pulp preferably has a structure in which a large number of fibril fibers having a diameter of 0.2 to 1 μm are branched from a fibrous trunk having a diameter of 5 to 20 μm. In order to make the sheet-like material of the present invention from these fibrous materials, a generally used nonwoven fabric manufacturing method, a method in which a dispersion of a pulp-like material is formed into a sheet by a papermaking method, and the like can be used. Preferred is a wet papermaking system that is advantageous for producing a porous sheet. When the sheet is formed by wet papermaking, it is necessary to transfer the wet sheet between nets during the papermaking process, and the wet sheet strength is required. This strength is obtained by entanglement of the fibers, and the branched structure of the acrylonitrile polymer pulp greatly contributes to the improvement of the strength of the porous sheet of the present invention. Such a structure is disclosed in
It can be efficiently generated by the method disclosed in JP-A-241917.

The short fibers contribute to an improvement in the strength in the longitudinal direction of the sheet. A typical manufacturing process of a lithium ion secondary battery is a process of applying tension to a laminate in which a separator is sandwiched between a positive electrode and a negative electrode and winding the laminate into a roll. Therefore, it is preferable that the porous sheet of the present invention, which is a gel electrolyte precursor, can be incorporated in the above-described manufacturing process as a substitute for the current separator, and has a strength that does not break the winding tension. As the proportion of short fibers increases, the strength in the longitudinal direction of the sheet increases, but if the short fibers are excessive, the denseness in the thickness direction decreases. Increase. Preferably, the mixing ratio of the acrylonitrile polymer short fiber and the pulp-like material is 25 to
50 wt% / 75 to 50 wt%.

The acrylonitrile-based polymer is a polymer containing acrylonitrile as a main component. From the viewpoint of gel formation with an organic electrolyte and the ionic conductivity of the resulting polymer gel, the acrylonitrile unit is composed of 50 mo.
It is preferable to contain 1% or more, especially 70 mol% or more.

As an ionic conductive polymer gel electrolyte used in a lithium secondary battery, polyacrylonitrile-based polymers, polyethylene glycol, polymethyl methacrylate, polyvinylidene fluoride, etc., which are soluble in an organic electrolyte, have been proposed. . Above all, acrylonitrile copolymers have higher porosity of the porous sheet of the present invention than other organic polymer materials because ionic conductivity, safety are ensured, and shaping into a fiber structure is easy. It can be configured efficiently.

The component to be copolymerized with acrylonitrile is not particularly limited as long as the solubility of the copolymer in a non-aqueous solvent and the ionic conductivity of the obtained polymer gel are not impaired. (Meth) acrylate, vinyl acetate, methacrylonitrile, vinyl chloride, vinylidene chloride, styrene and the like are used. Especially, it is preferable to copolymerize an acrylate unit or a vinyl acetate unit, and it is preferable that the copolymerization amount is 3 to 8 mol%. By copolymerizing such comonomers, these acrylonitrile polymers are
For example, dimethyl carbonate, diethyl carbonate,
Gel formation is possible even with an electrolyte containing a low-viscosity solvent such as ethyl methyl carbonate, and a gel electrolyte having high ionic conductivity even at low temperatures can be obtained.

In practicing the present invention, a short fiber or a pulp-like material made from two or more acrylonitrile-based polymers having different copolymerization monomer ratios or at least one copolymerization composition ratio is used. These acrylonitrile-based polymers differ in solubility, gel-forming property, or swelling property in a non-aqueous electrolyte. Therefore, by forming a fibrous sheet-like material mixed in the above ratio, the fibrous sheet is subjected to non-aqueous electrolysis. The solid polymer electrolyte prepared by impregnating the liquid is excellent in shape retention at high temperatures and non-aqueous electrolyte retention,
A product having high ionic conductivity at a low temperature of not more than ℃ can be obtained.

As a preferred method for producing the porous sheet of the present invention, a wet papermaking method can be preferably used.
In these papermaking methods, the above-described porous sheet having a thickness of 30 to 75 μm can be prepared by mixing and mixing acrylonitrile-based polymer pulp and short fibers. By heat-pressing the porous sheet, it is possible to produce a uniform porous sheet having a thickness of 20 to 40 μm. Also, in the manufactured porous sheet,
It has a moderate space between the fibers and does not require special porous treatment. The porosity of the sheet can be controlled by changing the shape such as the diameter of short fibers and the degree of branching of the pulp, the mixing ratio, the basis weight, the pressing temperature after papermaking, the pressure, and the like.

The non-aqueous electrolyte used for preparing the polymer gel electrolyte of the present invention comprises an electrolyte salt for conducting ionic conduction and a non-aqueous solvent for dissolving the electrolyte. As the electrolyte salt, various organic and inorganic electrolyte salts are used. For example, LiClO ₄ , LiBF ₄ , LiPF ₆ ,
LiCF ₃ SO ₃ , LiAsF ₆ , LiSCN, Li
I and LiAlO ₄ can be mentioned as typical examples. The non-aqueous solvent is required to have a high non-dielectric constant, to be chemically particularly electrochemically stable, to have excellent long-term storage stability, and to be used in cyclic carbonates,
It is preferable to use chain carbonates, for example,
Propylene carbonate, ethylene carbonate, cyclic carbonate such as butylene carbonate, cyclic ester such as γ-butyrolactone, tetramethylsulfolane,
N-methylpyrrolidone, dimethylformamide, dimethylacetamide, dimethylsulfoxide, hexamethylsulfamide, pyridine and derivatives thereof, as well as dimethoxyethane, ethoxymethoxyethane, chain ethers such as diethoxyethane, tetrahydrofuran,
Examples thereof include cyclic ethers such as dioxolan and dioxane, chain carbonates such as dimethyl carbonate and diethyl carbonate, derivatives thereof, acetonitrile, nitromethane, 1,3-dimethyl-2-imidazolidinone, and the like.

The polymer gel electrolyte of the present invention is prepared by impregnating the porous sheet material of the present invention with a non-aqueous electrolyte to gel the fibrous sheet material. A non-aqueous electrolyte is previously impregnated between the positive electrode active material sheet and the negative electrode active material sheet, and the gelled sheet-like polymer gel electrolyte of the present invention is sandwiched and fixed, or the positive electrode active material sheet and the negative electrode After the fibrous sheet material of the present invention is sandwiched between the active material sheet and the active material sheet, a method of impregnating with a non-aqueous electrolyte and gelling can be employed. The sheet-like material using the fibrous polymer of the present invention can be easily impregnated with a non-aqueous electrolyte and gelled, and can form a gel-like solid electrolyte layer compared to a conventionally developed polymer gel electrolyte. It is very easy and has a great feature that its handleability is good.

The impregnation ratio of the fibrous sheet material of the present invention and the non-aqueous electrolyte can be usually in the range of 95/5 to 10/90 (weight ratio), and more preferably 30/70 to 90/90.
The ratio is 10/90 (weight ratio). When the fibrous sheet of the present invention is impregnated with a non-aqueous electrolyte, the non-aqueous electrolyte is
Utilizing the capillary phenomenon of the fibrous sheet material of the present invention, it permeates uniformly between the fibers constituting the sheet material in a very short time. The optimum heating conditions for the sheet vary depending on the composition of the non-aqueous electrolyte, but the appropriate heating conditions are 50 to 75 ° C. and 1 to 1
5 minutes. When heated to a temperature higher than that, volatilization of the solvent and deterioration of the electrolyte salt occur, and the physical properties of the gel electrolyte deteriorate. On the other hand, if the heating is insufficient, the gel electrolyte is not sufficiently formed, which causes a soft short and a decrease in ionic conductivity. After the heating, the sheet is held at room temperature for 6 to 12 hours to obtain the gel electrolyte sheet of the present invention. Sheets made from short fibers, fibrils, or pulp can increase the surface area of the fibers themselves, so they have particularly good contact with non-aqueous electrolytes and polymer gel electrolytes in a short time. It has a great feature that it can be made. Further, since the fibrous sheet-like material of the present invention uses oriented fibers, a part of the fibers retains the structure even after immersion in the non-aqueous electrolyte, so that the sheet strength is maintained even after heating, No short circuit occurs when assembling the battery, and the productivity can be improved as compared to a battery production line using a polymer powder.

[0030]

The present invention will be described in more detail with reference to the following examples.

Example 1 An acrylonitrile copolymer having a polymer composition of 95 mol% of acrylonitrile and 5 mol% of vinyl acetate was added to dimethylacetamide at a concentration of 13 w.
It dissolved so that it might become t%. According to the method disclosed in JP-A-9-241917, a solution discharge port having a diameter of 0.2 mmφ and a diameter of 2 mm were prepared.
φ, a cylindrical mixing cell with a length of 10 mm, a water vapor flow path is slit-shaped, the opening is adjusted to 250 μm, and the angle between the center line of the solution flow path and the slit center line is 60 degrees. Using the nozzle, the supply amount of the polymer solution was 4
The mixture was jetted into water at a temperature of 30 ° C. at 0 ml / min and a supply pressure of steam of 0.39 MPa to obtain a pulp-like acrylonitrile copolymer.

The acrylonitrile copolymer pulp was dispersed in water and beaten for 10 minutes with a household mixer. A part of the aqueous dispersion after the beating treatment was taken out, and the pulp obtained by drying was subjected to morphological observation using a scanning electron microscope. From the fibrous trunk having a diameter of 5 to 20 μm, a large number of diameters were obtained. A structure in which fibril-like fibers of about 0.2 μm to 1 μm were branched was observed.

Next, 96.3 mol of acrylonitrile
%, And 3.7 parts by mass of methyl acrylate, 18 parts by mass of a polymer were dissolved in 82 parts by mass of dimethylacetamide to prepare an acrylonitrile polymer solution. This solution was extruded from a nozzle having a pore diameter of 0.027 mmφ into a coagulation liquid, washed, stretched and dried to obtain 0.2 dtex acrylonitrile fiber.

10 parts by mass of the acrylonitrile polymer pulp obtained as described above and 3 parts of acrylonitrile fiber
10 parts by mass cut into mm were mixed to prepare an aqueous dispersion of this mixture. Using this aqueous dispersion, wet papermaking was performed using a standard square sheet machine according to JIS P-8209.

The basis weight of the obtained fibrous sheet is 15 g.
/ M ² , and the average sheet thickness measured according to JISP-8118 was 61 μm. This sheet was cut to prepare a strip-shaped test piece, and a tensile strength test of the test piece was performed according to JIS P-8113. The 15 mm wide test specimen had a breaking strength of 6.3 N / 15 mm. The porosity of this sheet was calculated from the formula: porosity = (pore volume / sheet volume) × 100, and was 78%.

The porous sheet was subjected to press heat treatment using a press roll set at a surface temperature of 140 ° C. The sheet after the press heat treatment was a porous sheet having a sheet thickness of 30 μm, a tensile strength of 9.0 N / 15 mm width, and a porosity of 56%.

This porous sheet was punched into a round shape having a diameter of 42 mm. 1 mol / kg LiP as supporting electrolyte
Ethylene carbonate containing F ₆ (hereinafter, referred to as EC) / diethyl carbonate (hereinafter, referred to as DEC) mass ratio of 2: 1 mixed solution obtained by impregnating this punching sheet 3 times the fibrous sheet A non-aqueous electrolyte solution was supported. Subsequently, this porous sheet is 55 mm × 10 mm
Was cut into strips and immersed vertically in the DEC for 2 minutes.
Sucked up.

The sheet after the non-aqueous electrolyte impregnation operation was transferred to a closed container, kept at 65 ° C. for 3 minutes, and heat-treated.
Observation under crossed Nicols with a polarizing microscope using a polarizing microscope revealed that the anisotropic structure based on the pulp-like polymer was observed before heat treatment, but this anisotropic structure was observed after heat treatment. Was not observed. The evaluation of the electrical characteristics of the porous sheet containing the electrolyte after heating (hereinafter referred to as an electrolyte sheet) was measured by an AC impedance method using a precision LCR meter-4284A manufactured by Hewlett-Packard. The attachment for ion conductivity measurement used for the measurement had an opposite diameter of 14.8.
mm of a disc-shaped stainless steel electrode, and an electrolyte sheet was sandwiched between the electrodes. At the time of measurement, a load of 11.8 kPa was applied between both electrodes using a spring to keep the adhesion between the sample and the stainless steel electrode constant. Note that these operations were performed in a glove box replaced with argon. Frequency 1
An alternating current with a peak voltage of 20 mV was applied in the range of 00 Hz to 1 MHz, and the complex impedance of the sample was measured. The locus of the complex impedance obtained by the measurement was analyzed by the Cole-Cole plot method, and the ion conductivity was derived from the electrode area and the distance between the electrodes, with the point intersecting the real axis on the high frequency side as the resistance value of the sample. The ionic conductivity of the sample at 25 ° C. was 1.6 mS / cm.

Example 2 10 parts by mass of a polyacrylonitrile polymer pulp and 93 mol of acrylonitrile
%, 7 mol% of vinyl acetate, and 10 parts by mass of acrylonitrile fibers cut to 2 mm were mixed together, and wet-laid according to the same method as in Example 1 to obtain a sheet having a basis weight of 16 g / m ² .

When the obtained sheet was subjected to a press treatment using a press roll set at 140 ° C., the thickness of the sheet was 33 μm, and the tensile strength was 9.2 N / 15 m.
m, a porous sheet having a porosity of 57%. Subsequently, the porous sheet was cut into strips of 55 mm × 10 mm and immersed vertically in DEC for 2 minutes. This sheet sucked up DEC at a speed of 2.2 mm / min. This porous body was impregnated with the same electrolytic solution as in Example 1, heat-treated at 65 ° C. for 3 minutes, and kept at room temperature for 6 hours. The ionic conductivity was measured, and it was 1.7 mS / cm.

Comparative Example 1 The porous sheet used in Example 1 was impregnated with the same electrolytic solution as in Example 1, left at room temperature for 6 hours without heat treatment, and then measured for ionic conductivity. Was 0.62 mS / cm.

Comparative Example 2 18 parts by mass of the polyacrylonitrile pulp used in Example 2 and acrylonitrile 9
3 mol%, vinyl acetate 7 mol% acrylonitrile fiber cut to 2 mm 2 parts by mass were mixed,
Wet papermaking was performed in the same manner as in Example 1, and the basis weight was 28 g / m ^2.
Was prepared. When press processing was performed using a press roll set at 140 ° C., the thickness was 45 μm.
m, tensile strength 13.4N / 15mm, porosity 45%
Was obtained. Subsequently, this porous sheet is
Cut out into a 10 mm × 10 mm strip, and cut vertically into the DEC.
This sheet was immersed for 1.2 minutes
DEC was sucked up at the speed of. The porous sheet was impregnated with an electrolytic solution and heat-treated in the same manner as in Example 1, and the ionic conductivity was measured to be 0.24 mS / cm.

Comparative Example 3 Polyethylene used in Example 1
Wet papermaking from pulp only material, basis weight 25g / m ²No
I got it. The obtained sheet was pressed at 130 ° C.
Pressing using a sroll resulted in a thickness of 30
μm, tensile strength 12.4 N / 15 mm, porosity 18
% Porous sheet was obtained. Then, this porous sheet is
Cut out into a strip of 5mm x 10mm, perpendicular to DEC
When immersed for 2 minutes, this sheet was 0.6 mm / mi
DEC was sucked up at a speed of n. Example 1
The electrolyte was impregnated and heat-treated as in
The sheet cannot hold the electrolyte and leakage of the solution is remarkable.
Was.

[0044]

[Table 1]

[0045]

[Table 2]

[0046]

The porous sheet of the present invention is excellent in the retention of an electrolytic solution, and when impregnated with a non-aqueous electrolytic solution, swells and / or gels, and when used as an electrolytic sheet, the porous sheet and the non-aqueous electrolytic solution Swelling and / or gelling can be easily carried out due to the leakiness and impregnation of the resin, and on the other hand, it also has good mechanical properties. In addition, the solid electrolyte sheet of the present invention has a great feature that it has good handleability and does not leak electrolyte solution despite having high ionic conductivity. Since the shape is maintained afterwards, the fabrication of the battery is easy, and the productivity can be greatly improved.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Mitsuo Hamada, Inventor 20-1 Miyukicho, Otake City, Hiroshima Prefecture Inside Mitsubishi Rayon Co., Ltd. Central Technology Research Institute (72) Inventor Chinami Iida 201-1 Miyukicho, Otake City, Hiroshima Prefecture F-term in Central Research Laboratory of Mitsubishi Rayon Co., Ltd. (reference) 4L055 AF21 AF27 AF29 AF39 AF47 BE10 EA04 EA08 EA10 EA16 EA18 EA25 EA29 GA01 GA50 5H021 AA06 BB01 BB12 CC02 EE06 HH01 HH02 HH06 5H029 AJ12 AM03 AL06 DJ13 EJ11 HJ01 HJ04 HJ05 HJ09 HJ14

Claims (11)

[Claims] 1. A fibrous sheet comprising at least two or more types of acrylonitrile-based polymer fibrous materials, wherein when the fibrous sheet is immersed vertically with respect to the liquid surface of diethyl carbonate, diethyl carbonate A porous sheet material for forming a polymer gel electrolyte, which is a fibrous sheet having a function of sucking the electrolytic solution of 1.5 mm / min or more. 2. A porous sheet material having a porosity of 40 to 6
2. The porous sheet for forming a polymer gel electrolyte according to claim 1, wherein the porous sheet is formed of a material having a thickness of 0% and a thickness of 40 μm or less. 3. A fibrous material of an acrylonitrile-based polymer constituting a porous sheet-like material, comprising 25 to 50 watts of short fibers
3. The porous sheet for forming a polymer gel electrolyte according to claim 1, wherein the pulp comprises 75% to 50% by weight of a pulp obtained by branching a large number of fibril fibers from a fibrous trunk of the polymer gel. object. 4. The short fiber has a diameter of 1 to 20 μm,
The length is 2 to 5 mm.
The porous sheet for forming a polymer gel electrolyte according to any one of the above. 5. The method according to claim 1, wherein the copolymer component of the acrylonitrile-based polymer is at least one vinyl monomer selected from the group consisting of an acrylate ester and vinyl acetate. Item 8. The porous sheet material for forming a polymer gel electrolyte according to Item 1. 6. A copolymer composition ratio of a vinyl monomer selected from the group consisting of acrylate and vinyl acetate, which are copolymer components of the acrylonitrile-based polymer, is 3 to 6.
The porous sheet material for forming a polymer gel electrolyte according to claim 5, wherein the content is 8 mol%. 7. A polymer gel electrolyte, wherein the porous sheet material according to claim 1 is impregnated with a non-aqueous electrolyte to gel or swell. 8. A gel body having a polymer concentration of 10 wt% to 30 wt%, wherein the porous sheet material according to claim 1 is impregnated with a non-aqueous electrolyte. The polymer gel electrolyte according to claim. 9. The polymer gel according to claim 7, wherein the non-aqueous solvent constituting the non-aqueous electrolyte is at least two or more solvents selected from cyclic carbonates and chain carbonates. Electrolytes. 10. The non-aqueous solvent constituting the non-aqueous electrolytic solution contains 40% by mass or more of cyclic carbonate and 60% of chain carbonate.
The polymer gel electrolyte according to claim 9, wherein the polymer gel electrolyte is used in an amount of not more than mass%. 11. A non-aqueous electrolyte is impregnated in the porous sheet according to any one of claims 1 to 6, and a temperature of 50 to 75 ° C.
And a method for producing a polymer gel electrolyte obtained by gelling or swelling by heating at room temperature for 1 to 20 minutes and cooling at room temperature for 6 to 12 hours.