JP2000133310A - All solid secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an all solid secondary battery constructed small and light, equipped with excellent high capacity, large current discharging characteristic, unlikely to cause liquid leakage or fire breaking, having small interface impedance between a positive electrode, negative electrode and an electrolyte layer, and having good cyclic characteristics. SOLUTION: An all solid secondary battery is configured so that an electrolyte layer consisting of gel-form organic polymer electrolytic substance is inserted between a positive and a negative electrode and fixed, wherein the positive electrode is made of a positive electrode active material and gel-form organic polymer electrolyte while the negative electrode is formed from a negative electrode active material and gel-form organic polymer electrolyte. The gel-form organic polymer electrolyte should preferably consist of a compound including an organic polymer having a relative permittivity 4 or above, non- protonic solvent and electrolyte salt, or the organic polymer should preferably be acrylonitrile polymer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an all-solid-state secondary battery, and more particularly, to a small, lightweight, high-capacity battery that is unlikely to cause inconvenience of liquid leakage and fire, and has a positive electrode, a negative electrode, an electrolyte layer The present invention relates to an all-solid-state secondary battery having a small interfacial impedance between the two.

[0002]

2. Description of the Related Art A light-weight, high-capacity lithium secondary battery is obtained by binding a negative electrode active material such as a carbon material for doping / dedoping lithium ions with a polyvinylidene fluoride-based polymer binder, or lithium metal. Or a negative electrode comprising an alloy thereof, a positive electrode comprising a positive electrode active material such as lithium-containing transition metal chalcogenite bound with a polyvinylidene fluoride-based polymer binder, and
A non-aqueous secondary battery using an electrolyte composed of a non-aqueous electrolyte in which a metal salt is dissolved in an aprotic solvent is known.

[0003] In this type of lithium secondary battery, when the battery temperature rises, the aprotic solvent volatilizes inside the battery, so that the battery swells or the volatile gas diffuses from the leak valve. There is a problem that a leaked liquid is generated.

[0004] Lithium secondary batteries that are unlikely to cause such problems include polymers having a polyether bond in the main chain, polymethacrylate, polymethylmethacrylate, and the like.
Japanese Patent Application Laid-Open No. 7-82450 discloses a method using a solid electrolyte membrane comprising an organic polymer such as polyacrylonitrile, acrylonitrile-styrene copolymer, vinyl chloride-acrylonitrile copolymer, an aprotic solvent, and an electrolyte salt.
And Japanese Patent Application Laid-Open No. 7-32081.

[0005]

However, the positive electrode constituting this lithium secondary battery uses manganese dioxide (MnO ₂ ) as a positive electrode active material, graphite powder as a conductive material, and an aprotic solvent as a binder. Is formed by applying a uniform mixture of these to a current collector surface and pressing the same, using a polytetrafluoroethylene powder insoluble in water. The surface is relatively rough. Therefore, the adhesion between the positive electrode and the electrolyte layer cannot be said to be sufficient, the interface impedance between the positive electrode and the electrolyte layer becomes large, and a high-capacity, all-solid secondary battery excellent in large-current discharge characteristics is obtained. It was difficult. In addition, the battery is subjected to strong vibration or shock, or undergoes long-term expansion and contraction of the active material layer (positive electrode) due to lithium ion doping / de-doping, thereby causing interfacial delamination between layers and shortening the cycle life of the battery. Had the drawback of being easy to do.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a compact, lightweight, high-capacity, excellent large-current discharge characteristic, less likely to cause liquid leakage and inconvenience of fire, and an interface impedance between a positive electrode or a negative electrode and an electrolyte layer. It is to provide an all-solid-state secondary battery having a small cycle and good cycle characteristics.

[0007]

The inventors of the present invention have studied to solve the above-described problems, and as a result, have found that a film-like solid (gel-like solid) comprising a polymer having a high relative dielectric constant, an electrolyte salt, and an aprotic solvent. ) On both sides of the electrolyte layer, a laminate is formed by bonding a positive electrode and a negative electrode, each of which is formed using a gel electrolyte comprising an organic polymer having a high relative dielectric constant and an aprotic solvent as a binder for the positive electrode active material and the negative electrode active material. The all-solid-state secondary battery of the present invention having at least one is completed.

That is, the all-solid secondary battery of the present invention is an all-solid secondary battery having a structure in which an electrolyte layer made of a gel organic polymer electrolyte is inserted and fixed between a positive electrode and a negative electrode. Is composed of a positive electrode active material and a gelled organic polymer electrolyte, and the negative electrode is composed of a negative electrode active material and a gelled organic polymer electrolyte. Further, it is desirable that the gel organic polymer electrolyte is composed of a uniform composition having an organic polymer having a relative dielectric constant of 4 or more, an aprotic solvent, and an electrolyte salt. The organic polymer is preferably an acrylonitrile-based polymer. Also,
The acrylonitrile-based polymer is preferably a (co) polymer containing 50 mol% or more of acrylonitrile units.

The positive electrode is formed by gelling a composition comprising an acrylonitrile-based polymer, an aprotic solvent, an electrolyte salt, and a positive electrode active material, and is gelled. The negative electrode is formed of acrylonitrile. The composition may be formed into a film having a system polymer, an aprotic solvent, an electrolyte salt, and a negative electrode active material, and may be gelled. Further, the positive electrode is an acrylonitrile-based polymer, polyvinylidene fluoride, an aprotic solvent, an electrolyte salt, and a film formed of a composition having a positive electrode active material, and the positive electrode is formed by gelation, May be obtained by forming a film of a composition containing an acrylonitrile-based polymer, polyvinylidene fluoride, an aprotic solvent, an electrolyte salt, and a negative electrode active material, and gelling the composition. Further, the electrolyte layer has an acrylonitrile-based polymer, an aprotic solvent, and a composition having an electrolyte salt, or an acrylonitrile-based polymer, polyvinylidene fluoride, an aprotic solvent, and an electrolyte salt. The composition may be gelled. Also,
The electrolyte layer is formed by impregnating any one of a woven fabric, a nonwoven fabric, and a paper-like material made of fibers or pulp-like materials made of an acrylonitrile-based polymer with an aprotic solvent in which an electrolyte salt is dissolved, and this gels. May be done.

It is preferable that the aprotic solvent contains a carbonate-based solvent. It is preferable that a current collector made of a metal thin film is provided on the surface of the positive electrode or the negative electrode. Further, as the negative electrode, lithium metal or a lithium alloy may be used instead of the negative electrode active material and the gel organic polymer electrolyte. Further, the woven fabric, nonwoven fabric or paper-like material constituting the electrolyte layer is a pulp-like material made of an acrylonitrile polymer, at least one kind of fiber, and a fiber, pulp-like, fibril-like material made of vinylidene fluoride or polyolefin. It may be composed of a mixture with at least one of the substances.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The positive electrode of the all solid state secondary battery of the present invention comprises a positive electrode active material and a gel organic polymer electrolyte, and the negative electrode comprises a negative electrode active material and a gel organic polymer electrolyte. Further, the electrolyte layer of the all solid state secondary battery of the present invention is made of a gel organic polymer electrolyte. As the positive electrode active material used for the positive electrode of the all solid state secondary battery of the present invention, for example, LiCoO ₂ , LiMnO ₂ , LiNiO
_Although transition metal chalcogenites such as ₂ are preferably used, any compound can be used as long as it can dope and undope lithium ions. In addition, the negative electrode active material used for the negative electrode may be any material that can be doped and dedoped with lithium ions. Examples thereof include pyrolytic carbons, cokes (pitch coke, needle coke, etc.), graphite, glassy carbons, and the like. And an organic polymer fired body (a fired product of a phenol resin, a furan resin, polyacrylonitrile, polyvinyl alcohol, or the like) or the like can be used.

The above-mentioned gelled organic polymer electrolyte is desirably composed of a uniform composition having an organic polymer having a relative dielectric constant of 4 or more, an aprotic solvent, and an electrolyte salt. When the relative permittivity of the organic polymer is 4 or more, the ion mobility in the all-solid secondary battery can be improved. Examples of the organic polymer having a dielectric constant of 4 or more used to form the gel organic polymer electrolyte include acrylonitrile-based polymers, polyvinylidene fluoride, and polyoxymethylene. Among them, acrylonitrile-based polymers are preferred, and (co) polymers containing 50 to 100 mol% of acrylonitrile units are particularly preferred.

Examples of monomers copolymerizable with acrylonitrile include acrylic acid, methacrylic acid, itaconic acid, styrenesulfonic acid, vinyl acetate, vinyl chloride,
Examples include styrene, vinyl propionate, acrylates and methacrylates having an alkyl ester group having 4 or less carbon atoms, butadiene, and isoprene. Among them, as a monomer copolymerizable with acrylonitrile, a monomer containing a carboxylic acid is used in an amount of 0.1 to 2;
When used in an amount of 0% by weight, the effect of improving the adhesion is exhibited. When an acrylonitrile-based polymer is used as the organic polymer, the content of the acrylonitrile unit is desirably 50 mol% or more, preferably 80 mol% or more, and more preferably 85 mol% or more.
When the content of the acrylonitrile unit is large, the solubility in an aprotic solvent can be kept good, and the ionic conductivity of the obtained gelled solid electrolyte can be made good.

These acrylonitrile-based polymers have a high affinity for aprotic solvents, are easy to form a gel-like organic polymer electrolyte, have a high affinity for an electrolyte salt, and have a high ionic conductivity gel polymer. Therefore, it is suitable for increasing the capacity of the all solid state secondary battery of the present invention. In addition, the adhesion between the positive electrode or the negative electrode using the organic polymer as a binder and the electrolyte layer formed using the organic polymer is extremely good, and the interface adhesion between each electrode and the electrolyte layer is high. Become. for that reason,
The battery has a great feature that it can be a battery having low interface impedance and a solid battery that is unlikely to cause interface delamination. In addition, when using an acrylonitrile-based polymer as a binder for the positive electrode active material or the negative electrode active material, a mixture of polyvinylidene fluoride is used for the purpose of improving film forming properties, mechanical strength of the binder layer, and flexibility of the electrode. May be used.

As the aprotic solvent used for the gelled organic polymer electrolyte, any aprotic solvent that has been used as a solvent for forming an electrolytic solution of a conventional lithium secondary battery can be used. For example, ethylene carbonate (relative dielectric constant 90), propylene carbonate (relative dielectric constant 65), dimethyl carbonate (relative dielectric constant 3.1), and diethyl carbonate (relative dielectric constant 2. 1).
8), tetrahydrofuran (dielectric constant 7.4), γ-butyrolactone (dielectric constant 42) and the like. In the present invention, the relative dielectric constant is 10 or more, especially 20
It is preferable to use a solvent mainly containing the above aprotic solvent. These aprotic solvents may be used alone, or a mixture of two or more thereof may be used. The all-solid secondary battery of the present invention using an aprotic solvent having a relative dielectric constant of 10 or more, particularly 20 or more, has good adhesion between the positive electrode or the negative electrode and the organic polymer electrolyte layer, and has an interlayer impedance. Low rechargeable battery.

As the electrolyte salt used for the gel organic polymer electrolyte, any electrolyte salt which has been used as a conventional electrolyte salt for a lithium secondary battery can be used. For example, LiPF ₆ , LiClO ₄ , Li
BF ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , Li (CF ₃
SO ₂ ) ₂ N or the like can be used. Further, a conductive material can be added to the positive electrode. Examples of the conductive material include acetylene black, graphite (flake graphite, granular graphite), carbon black, and Ketjen black.

It is desirable to provide a current collector on the surface of the positive electrode or the negative electrode of the all solid state secondary battery of the present invention. As the current collector, for example, aluminum foil, copper foil, nickel foil,
A metal thin film such as a stainless steel foil may be used. It is preferable that these current collectors are appropriately selected and used depending on the purpose. Further, as the negative electrode of the all-solid secondary battery of the present invention, lithium or a lithium alloy may be used instead of a gel organic polymer electrolyte containing a negative electrode active material.

As a method of forming a positive electrode or a negative electrode, for example, a predetermined amount of a positive electrode active material or a negative electrode active material is uniformly mixed with a solution in which an organic polymer and an electrolyte salt are dissolved in an aprotic solvent. A method in which the mixture is uniformly applied to one or both surfaces of the metal foil for a current collector, a solvent is volatilized appropriately, and then gelling can be used. At this time, when dissolving the organic polymer and the electrolyte salt in an aprotic solvent, after sufficiently swelling the organic polymer in the solvent, it is possible to increase the solubility of the organic polymer by heating the solvent to such an extent that the solvent does not evaporate. It is valid. By cooling the heated and dissolved organic polymer solution after coating, the coating film changes from a fluid sol state to a gel state having no fluidity and a solvent retaining ability. When the amount of the solvent in the organic polymer solution is large, a method of obtaining a gel having a predetermined composition by partially evaporating the solvent after application by a technique such as reduced pressure and heating may be used.

In another method, a predetermined amount of a positive electrode active material or a predetermined amount of a negative electrode active material is uniformly mixed with a solution in which an organic polymer is dissolved in a highly soluble organic solvent and, if necessary, an electrolyte salt. Then, the paste-like mixture is uniformly coated on one or both surfaces of the metal foil for a current collector, and the organic solvent is completely volatilized by heating or the like, followed by impregnation with an aprotic solvent and gelation. Is mentioned. At this time, the aprotic solvent to be impregnated is preferably subjected to the impregnation operation as an electrolytic solution in which an electrolyte salt is dissolved in order to accelerate the diffusion of the solvent into the organic polymer.

When polyvinylidene fluoride is used together with an acrylonitrile-based polymer as a binder for forming a positive electrode or a negative electrode, these organic polymers, a positive electrode active material or a negative electrode active material, and, in some cases, an electrolyte salt are converted into acrylonitrile. After dissolving both the base polymer and polyvinylidene fluoride in an organic solvent that dissolves the solution, applying this solution to the surface of the metal foil for a current collector and completely volatilizing the organic solvent by heating, etc., the aprotic solvent May be used. At this time, dimethyl sulfoxide, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2 are used as organic solvents for dissolving both the acrylonitrile-based polymer and polyvinylidene fluoride.
-Pyrrolidone and the like can be used. Further, an aprotic solvent for forming an electrolyte may be appropriately mixed and used in this solvent. Further, the aprotic solvent to be impregnated is preferably subjected to the impregnation operation as an electrolytic solution in which an electrolyte salt is dissolved, for the purpose of accelerating the diffusion of the solvent into the organic polymer.

The electrolyte layer is formed by uniformly dissolving an electrolyte salt and an organic polymer in an aprotic solvent and coating the same on a mold release material or sheet surface in the same manner as the method for forming a positive electrode or a negative electrode. Alternatively, a method of casting and gelling this can be used. In particular, a method in which an electrolyte salt and an organic polymer are dissolved in an aprotic solvent by heating, and the resulting solution is applied or cast on a sheet surface or the like and then cooled to be gelled is preferable.

As a method for forming the electrolyte layer, a sheet-like material such as a non-woven fabric, a woven fabric, a paper-like material made of acrylonitrile-based polymer fiber or pulp is sandwiched between the positive electrode and the negative electrode. A method of impregnating an aprotic solvent in which an electrolyte salt is dissolved in a substance and dissolving and gelling the same can also be used. Also, at this time, by using a combination of fibers made of polyvinylidene fluoride or polyolefin insoluble in an aprotic solvent, pulp, fibrils, etc., a gel electrolyte layer having high mechanical strength and good handleability. Can be.

The all-solid secondary battery of the present invention can be manufactured by using at least one laminate in which a positive electrode and a negative electrode are joined on both sides of the electrolyte layer manufactured as described above. The adhesiveness between the electrolyte layer of the all-solid secondary battery thus prepared, the positive electrode, and the negative electrode interface is good,
Even when the all-solid secondary battery of the present invention is used under severe conditions,
No interfacial delamination occurs, and the battery has extremely good cycle characteristics.

Furthermore, the adhesion between the positive electrode and the negative electrode and the electrolyte layer is greatly improved by stacking the respective layers and then performing a heat treatment to such an extent that the deterioration of the active material is not promoted. In particular, after performing heat treatment near the sol-gel transition temperature of the gel-like organic polymer electrolyte, by cooling, the positive electrode, the negative electrode, and the electrolyte layer adhere to each other, and the adhesion is dramatically improved.

Further, the all-solid-state secondary battery of the present invention has a very small interface impedance, a high capacity, and a high current discharge characteristic because of good bonding properties at the electrode interface. Has features.

[0026]

The present invention will be described below in detail with reference to examples.

Example 1 (Preparation of polymer) Acrylonitrile was added to a 2000 ml glass-made reaction vessel equipped with a jacket under the condition that the water / monomer ratio was 14/1.
3.6 mol%, 6.4 mol% of vinyl acetate was charged,
1.0% by weight of Na ₂ S based on the reaction solution as a polymerization catalyst
Aqueous suspension polymerization was carried out using O ₃ , 1.5% by weight of NaHSO ₃ and 0.12% by weight of H ₂ SO ₄ . Reaction temperature is 5
It was kept at 5 ° C. The polymer produced in the reaction vessel was collected, washed sufficiently, and dried to obtain a white powder. The reaction yield was calculated from the weight of the obtained powder to be 73%.

When the composition of the obtained polymer was analyzed by elemental analysis, it was found that acrylonitrile was 96.0 mol.
%, Vinyl acetate was 4.0 mol%.
The molecular weight of this polymer measured by GPC was 5.1 × 10 ^{5 in} terms of polystyrene. Here, GPC measurement was performed using 0.01 M Li as a solvent.
The polymer concentration was 0.1 g / dl using Cl / DMF.

(Preparation of Positive Electrode) Lithium-cobalt composite oxide (LiCoO ₂ ) was used as a positive electrode active material, and 50 parts by weight of the positive electrode active material was 5 parts by weight of acetylene black as a conductive material and the above-mentioned acrylonitrile / binder was used as a binder polymer. 5 parts by weight of a vinyl acetate copolymer was added and mixed with an appropriate amount of N-methylpyrrolidone to prepare a paste. Preparation was performed under a nitrogen atmosphere. This paste is uniformly applied on an aluminum foil (thickness: 20 μm) of a positive electrode current collector under an argon atmosphere, and then heated to be N 2.
-Methylpyrrolidone was completely volatilized, and further pressed under pressure to form a positive electrode having a thickness of 50 μm.

(Preparation of Negative Electrode) Amorphous carbon powder was used as a negative electrode active material, and 4 parts by weight of the acrylonitrile / vinyl acetate copolymer as a binder polymer was added to 60 parts by weight of this carbon powder. -Methylpyrrolidone to prepare a paste. Preparation was performed under a nitrogen atmosphere. This paste was uniformly applied on a copper foil (thickness: 30 μm) of a negative electrode current collector under an argon atmosphere, and then heated to completely volatilize N-methylpyrrolidone. 60μm thick
Was formed.

(Preparation of Solid Electrolyte Membrane) To 11 parts by weight of the acrylonitrile / vinyl acetate copolymer, 89 parts by weight of an electrolyte obtained by dissolving LiPF ₆ in propylene carbonate so as to have a concentration of 1 M / liter were added, followed by swelling and heating. -A uniform paste was prepared by mixing. Preparation was performed under a nitrogen atmosphere. The paste was uniformly applied on a 200 μm-thick polyester film under an argon atmosphere. When slowly cooled to room temperature after coating, the coating liquid lost its fluidity and formed an opaque gel-like organic polymer electrolyte membrane. When the thickness of this film was measured, it was 9
It was 5 μm.

The electric conductivity of the thus prepared polymer solid electrolyte membrane was measured by an alternating current impedance method using a precision LCR meter 4284A manufactured by Hewlett-Packard. The attachment for electric conductivity measurement used for the measurement was made of a disc-shaped stainless steel electrode having a diameter of 14.8 mm facing the electrode, and the measurement was performed with a polymer solid electrolyte interposed 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.

An alternating current having a peak voltage of 20 mV was applied in a frequency range of 100 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 electrical conductivity was derived from the electrode area and the inter-electrode distance, with the point intersecting the real axis on the high frequency side as the resistance value of the sample. The electrical conductivity of the sample at 25 ° C. was 6.8 × 10 ⁻³ S / cm.

(Formation of Secondary Battery) Using the above positive electrode, negative electrode and solid electrolyte membrane, a thin-film type all solid secondary battery as shown in FIG. 1 was assembled. The positive electrode 1 and the negative electrode 2 are punched into a disk shape having a diameter of 25 mm, and the solid electrolyte membrane 3 is punched into a disk shape having a diameter of 27 mm, and the positive electrode 1, the solid electrolyte film 3, and the negative electrode are placed on a stainless steel electrode 5 provided in a dedicated fluororesin cell 4. 2
, And a stainless steel electrode 6 was placed on the negative electrode 2. At this time, the positive electrode 1 is laminated with the positive electrode active material layer 7 facing the solid electrolyte membrane 3 side and the positive electrode current collector 8 facing the stainless steel electrode 5 side, and the negative electrode 2 is laminated with the negative electrode active material layer 9 facing the solid electrolyte membrane 3. The negative electrode current collector 10 was laminated toward the stainless steel electrode 6 side. Next, a predetermined pressure was applied to the stacked body by the spring 11 to obtain a secondary battery. The load pressure was 9.8 kPa. This operation was all performed in a glove box purged with argon.

In the all-solid-state secondary battery formed according to the above procedure, a part of the electrolyte contained in the solid electrolyte membrane 3 comes into contact with the positive electrode 1 and the negative electrode 2.
By being immersed in the positive electrode 1 and the negative electrode 2 and impregnated with an acrylonitrile / vinyl acetate copolymer as a binder polymer, the binder polymer is converted into a solid electrolyte. In this process, the polymer used for the solid electrolyte membrane 3 and the positive electrode 1 and the negative electrode 2 has the same composition and high affinity, so that the process proceeds smoothly, and as a result, the adhesion is good, A secondary battery having low interface impedance and low internal resistance and excellent electric characteristics can be obtained.

(Measurement of Discharge Capacity) The secondary battery prepared as described above was charged at room temperature (24 ° C.) to 4.0 V at 2.45 mA, and then discharged to 2.0 V at 2.45 mA. Charge / discharge test with one cycle as
The discharge capacity at the cycle was determined. The discharge capacity of this secondary battery was 52 mAh. The capacity retention of this battery was defined as the ratio of the discharge capacity after the 30th cycle to the discharge capacity at the 5th cycle, and was found to be 82%.

(Evaluation of Adhesion Characteristics) In the secondary battery prepared as described above, the adhesion between the positive electrode 1 and the negative electrode 2 and the solid electrolyte membrane 3 was evaluated. Each layer adheres to each other,
It was solvated and no bleeding of the solvent was observed.

[Example 2] (Preparation of polymer) In the same manner as in Example 1, acrylonitrile unit was 96.0 mol.
An acrylonitrile polymer having a composition of 1% and a vinyl acetate unit of 4.0 mol% was obtained.

(Preparation of Positive Electrode / Negative Electrode) A paste prepared in the same manner as in Example 1 using the acrylonitrile-based polymer as a binder was coated on a metal foil as a current collector and gelled to form a positive electrode. And a negative electrode were produced.

(Preparation of Solid Electrolyte Membrane) JP-A-9-241
According to the method disclosed in Japanese Patent No. 917, a solution discharge port having a diameter of 0.2 mmφ, a cylindrical mixing cell portion having a diameter of 2 mmφ and a length of 1.5 mm, and a steam flow path opened in a slit shape. Of the polymer solution was supplied using a nozzle prepared such that the angle between the center line of the solution flow path and the center line of the slit was 60 degrees.
The N, N-dimethylacetamide solution of the acrylonitrile-based polymer is jetted into water at a temperature of 30 ° C. under the conditions of 1.5 kg / cm ² and a steam supply pressure of 1.5 kg / cm ² to obtain acrylonitrile-based polymer pulp fibers. Was. Using the aqueous dispersion of pulp-like fibers obtained as described above, wet papermaking is performed by a standard square sheet machine in accordance with JIS P-8209, and the basis weight is 25 g / m ² and the average sheet thickness is 155.
A fibrous sheet made of an acrylonitrile polymer having a thickness of μm was obtained.

The fibrous sheet was punched out into a round shape having a diameter of 42 mm using a punching machine, and 1
A propylene carbonate solution containing M / kg LiPF ₆ was impregnated. The sheet after the impregnation operation was transferred to a closed vessel and kept at 80 ° C. for 12 hours to perform a heat treatment, and the impregnated sheet was swollen and gelled to obtain a solid electrolyte membrane. The electrical conductivity of this sheet at 25 ° C. is 5.4 × 10
^-3 S / cm.

(Preparation of Secondary Battery) A thin-film type all-solid secondary battery was assembled in the same manner as in Example 1 using the above-described positive electrode, negative electrode and solid electrolyte membrane.

(Measurement of Discharge Capacity) The secondary battery prepared as described above was charged at room temperature (24 ° C.) at 2.45 mA to 4.0 V, and then discharged at 2.45 mA to 2.0 V. Charge / discharge test with one cycle as
The discharge capacity at the cycle was determined. The discharge capacity of this secondary battery was 49 mAh. The capacity retention of the battery was defined as the ratio of the discharge capacity after 30 cycles to the discharge capacity at the 5th cycle, and was measured to be 86%.

(Evaluation of Adhesion Characteristics) The secondary battery after the discharge test was disassembled, and the adhesion between the positive electrode and the negative electrode and the solid electrolyte membrane was evaluated. Each layer is in close contact with each other,
No seepage of the solvent was observed.

Example 3 (Preparation of Polymer) An acrylonitrile-based polymer having a composition of 96.0 mol% of acrylonitrile units and 4.0 mol% of vinyl acetate units was obtained in the same manner as in Example 1.

(Preparation of Positive Electrode / Negative Electrode) A paste prepared in the same manner as in Example 1 using the acrylonitrile-based polymer as a binder is coated on a metal foil as a current collector, and gelled to form a positive electrode. And a negative electrode,
It was punched into a disk-shaped electrode having a diameter of 25 mm.

(Preparation of Acrylonitrile Fiber Nonwoven Fabric) The above acrylonitrile unit was 96.0 mol.
%, 25 parts by weight of an acrylonitrile-based polymer having a vinyl acetate unit of 4.0 mol% in dimethylacetamide 75
The acrylonitrile-based fiber having a single fiber fineness of 1.0 denier was obtained by dissolving it in parts by weight and wet spinning. 70 parts by weight of chopped fiber obtained by cutting this fiber to 5 mm and polypropylene pulp (SWP manufactured by Mitsui Chemicals, Inc.)
Y600) Disperse 30 parts by weight in water by a predetermined method, make a paper according to the JISP-8209 method using a standard square sheet machine, dry, heat-treat under pressure at 165 ° C, and form a paper-like nonwoven fabric. I got a sheet. The polypropylene pulp in the obtained nonwoven fabric sheet was thermally fused to each other to form a porous support phase. The basis weight of the nonwoven fabric sheet obtained as described above was 42 g / m ² and the thickness was 65 μm, and the tensile strength of this sheet was 15 mm width and 28.7 N. This nonwoven fabric sheet was an opaque white material similar to paper. This nonwoven fabric sheet was punched into a disk having a diameter of 27 mm to form a nonwoven fabric for forming a solid electrolyte.

(Preparation of Secondary Battery) The non-woven fabric for forming a solid electrolyte was placed on the electrode surface (positive electrode active material layer) of the positive electrode, and the negative electrode surface was formed on the other surface of the non-woven fabric for forming a solid electrolyte. (Negative electrode active material layer), a stainless steel electrode is placed on the bottom of the fluororesin cell, and a negative electrode / nonwoven fabric for solid electrolyte formation / positive electrode is placed thereon, and a stainless steel electrode is placed thereon. Then, pressure was applied by a spring pressure. After impregnating the assembled laminate with the electrolytic solution used in Example 1, heat treatment is performed by holding the laminate at 80 ° C. for 12 hours to dissolve and gel the acrylonitrile-based polymer of the non-woven fabric for forming a solid electrolyte. A film was formed to obtain a secondary battery.

(Measurement of Discharge Capacity) A charge / discharge test of the secondary battery produced as described above was performed in the same manner as in Example 1. As a result, the discharge capacity of this secondary battery was 51 mAh.
The capacity retention of this battery was defined as the ratio of the discharge capacity after 30 cycles to the discharge capacity at the 5th cycle, and was measured to be 88%.

(Evaluation of Adhesion Characteristics) The secondary battery after the discharge test was disassembled, and the adhesion between the positive electrode and the negative electrode and the solid electrolyte membrane was evaluated. Each layer is in close contact with each other,
No seepage of the solvent was observed.

Example 4 (Preparation of Polymer) An acrylonitrile polymer having a composition of 96.0 mol% of acrylonitrile units and 4.0 mol% of vinyl acetate units was obtained in the same manner as in Example 1.

(Preparation of Positive Electrode / Negative Electrode) In the same manner as in Example 1, a paste prepared using the acrylonitrile-based polymer as a binder was coated on a metal foil as a current collector and gelled. A positive electrode and a negative electrode were produced.

(Preparation of Solid Electrolyte Membrane) 18 parts by weight of the acrylonitrile-based polymer was dissolved in dimethylacetamide 82
By dissolving in a part by weight and spinning, the fineness of a single fiber is 0.1.
An acrylonitrile fiber of 2 denier was obtained. After cutting this fiber to 5 mm, the fiber concentration becomes 0.3% by weight.
To prepare a liquid dispersed in water together with a viscous agent.
5 m / min of polypropylene fiber woven fabric with a basis weight of 50 g / m ²
An aqueous dispersion of the acrylonitrile-based polymer fiber is supplied while running on the net at a speed of, and the polyacrylonitrile-based cut fiber is entangled in a polypropylene fiber woven fabric by a high-pressure water flow, and then dried. The weight ratio of polyacrylonitrile fiber is 2/3,
A composite sheet having a thickness of 350 μm was prepared.

When this composite sheet was heat-treated under pressure between press rolls set at 170 ° C., which is higher than the melting point of the polypropylene fiber, the polypropylene was thermally fused to each other to form a porous support phase. Was. The thickness of this composite sheet was 142 μm. After impregnating the composite sheet with the electrolytic solution in the same manner as in Example 2, the composite sheet was transferred to a closed container and kept at 80 ° C. for 12 hours to perform a heat treatment, thereby swelling and gelling the impregnated sheet to obtain a solid electrolyte membrane. . The thickness of the solid electrolyte membrane was about 125 μm, and the conductivity at room temperature was 8.6 × 10 ⁻³ S / cm.

(Preparation of Secondary Battery) In the same manner as in Example 1, a thin-film type all-solid secondary battery was assembled using the above-described positive electrode, negative electrode and solid electrolyte membrane.

(Measurement of Discharge Capacity) A charge / discharge test of the secondary battery prepared as described above was performed in the same manner as in Example 1. As a result, the discharge capacity of the secondary battery was 38 mAh.
The capacity retention of the battery was defined as the ratio of the discharge capacity after 30 cycles to the discharge capacity at the 5th cycle, and was measured to be 86%.

(Evaluation of Adhesion Characteristics) The secondary battery after this discharge test was disassembled, and the adhesion between the positive electrode and the negative electrode and the solid electrolyte membrane was evaluated. Each layer is in close contact with each other,
No seepage of the solvent was observed.

Example 5 An acrylonitrile / vinyl acetate copolymer having an acrylonitrile unit of 93.5 mol% and a vinyl acetate unit of 6.5 mol% was prepared in the same manner as in Example 1. The molecular weight of the polymer obtained here was 4.0 × 10 ⁵ . Further, a positive electrode, a negative electrode and a solid electrolyte membrane were prepared in the same manner as in Example 1 using the acrylonitrile-based polymer. At this time, a solvent obtained by mixing 30 parts by weight of propylene carbonate (relative dielectric constant: 65), 40 parts by weight of ethylene carbonate (relative dielectric constant: 90), and 30 parts by weight of diethyl carbonate (relative dielectric constant: 2.8) was used as an electrolytic solution. 1M LiPF ₆ as supporting electrolyte
Per liter was used. The electric conductivity of the obtained solid electrolyte membrane is 9.4 × 10 ⁻² S
/ Cm.

As in Example 1, a secondary battery was constructed by combining the positive electrode, the negative electrode and the solid electrolyte membrane produced as described above, and the charge / discharge characteristics were measured. The discharge capacity was 54 mAh, and the capacity was maintained. The rate was 92%. Also,
There was no problem in the adhesion between the positive and negative electrodes and the solid electrolyte membrane.

Example 6 An acrylonitrile / ethyl acrylate copolymer having an acrylonitrile unit of 98.4 mol% and an ethyl acrylate unit of 1.6 mol% was prepared in the same manner as in Example 1. The molecular weight of the obtained polymer was 4.5 × 10 ⁵ . A positive electrode, a negative electrode, and a solid electrolyte membrane were prepared in the same manner as in Example 1. At this time, as in the case of Example 2, the solvent used was a mixture of 30 parts by weight of propylene carbonate, 40 parts by weight of ethylene carbonate, and 30 parts by weight of diethyl carbonate, and LiPF ₆ was 1 M / liter as a supporting electrolyte. Was used. The electric conductivity of the obtained solid electrolyte membrane is 8.9 × 10 ⁻² S / cm.
Met.

A secondary battery was constructed by combining the positive electrode, the negative electrode and the solid electrolyte membrane in the same manner as in Example 1, and the charge / discharge characteristics were measured. The discharge capacity was 51 mAh and the capacity retention was 91%. In addition, there was no problem in the adhesion between the positive and negative electrodes and the solid electrolyte membrane.

[Example 7] In the same manner as in Example 1, the acrylonitrile unit was 100 mol%, and the relative dielectric constant was 6.5.
Acrylonitrile polymer was prepared. The molecular weight of the polymer obtained here was 3.8 × 10 ⁵ . A positive electrode, a negative electrode, and a solid electrolyte membrane were prepared in the same manner as in Example 1. At this time, a solution prepared by dissolving LiPF ₆ at a concentration of 1 M / liter as a supporting electrolyte in a solvent obtained by mixing 80 parts by weight of propylene carbonate and 20 parts by weight of ethylene carbonate as an electrolytic solution was used. The electric conductivity of the solid electrolyte obtained here was 5.3 × 10 ⁻³ S / cm.

A secondary battery was constructed by combining the positive electrode, the negative electrode, and the solid electrolyte membrane in the same manner as in Example 1. The charge / discharge characteristics were measured. The discharge capacity was 53 mAh and the capacity retention was 89%. . In addition, there was no problem in the adhesion between the positive and negative electrodes and the solid electrolyte membrane layer.

Comparative Example 1 An acrylonitrile polymer containing 100 mol% of acrylonitrile units was prepared in the same manner as in Example 1. The molecular weight of the polymer obtained here was 3.8 × 10 ⁵ . As an electrolytic solution, a solution prepared by dissolving LiPF ₆ at a concentration of 1 M / liter as a supporting electrolyte in a solvent in which 30 parts by weight of propylene carbonate, 40 parts by weight of ethylene carbonate, and 30 parts by weight of diethyl carbonate was used was used. An attempt was made to dissolve the polymer powder, but the polymer powder only partially swelled and was not dissolved.

Example 8 (Preparation of polymer) An acrylonitrile / vinyl acetate copolymer having an acrylonitrile unit of 93.5 mol% and a vinyl acetate unit of 6.5 mol% was prepared in the same manner as in Example 1. The molecular weight of the polymer obtained here is 4.
It was 0 × 10 ⁵ .

(Preparation of Positive Electrode) Lithium-cobalt composite oxide (LiCoO ₂ ) was used as a positive electrode active material, and 50 parts by weight of the positive electrode active material was 5 parts by weight of acetylene black as a conductive material, and the above-mentioned acrylonitrile / binder was used as a binder polymer. 3 parts by weight of the vinyl acetate copolymer and 2 parts by weight of polyvinylidene fluoride were added and mixed. 50 parts by weight of an electrolytic solution obtained by dissolving LiPF _{6 in} N-methylpyrrolidone at a concentration of 0.2 M / liter was added to this mixture, and the mixture was heated and mixed to prepare a uniform paste. Preparation was performed under a nitrogen atmosphere. This paste was uniformly applied on an aluminum foil of a positive electrode current collector under an argon atmosphere, and the solvent was volatilized in a hot-air dryer set at 150 ° C. After drying, the coating solution formed a hard film. This film was further immersed in an electrolyte solution obtained by dissolving LiPF ₆ in propylene carbonate at a concentration of 1 M / liter at room temperature for 10 hours to swell the film.

(Preparation of Negative Electrode) Amorphous carbon powder was used as a negative electrode active material, and 3 parts by weight of the acrylonitrile / vinyl acetate copolymer and 3 parts by weight of polyvinylidene fluoride Parts by weight were added and mixed. LiP to N-methylpyrrolidone
50 parts by weight of an electrolytic solution in which F ₆ was dissolved at a concentration of 0.2 M / liter was added to this mixture, and the mixture was heated and mixed to prepare a uniform paste-like substance. Preparation was performed under a nitrogen atmosphere. This paste was uniformly coated on a copper foil of a negative electrode current collector under an argon atmosphere.
The solvent was volatilized in a hot air dryer set at 0 ° C. After drying, the coating solution formed a hard film. This film was further immersed in an electrolyte solution obtained by dissolving LiPF ₆ in propylene carbonate at a concentration of 1 M / liter at room temperature for 10 hours to swell the film.

(Preparation of Solid Electrolyte Membrane) To 11 parts by weight of the acrylonitrile / vinyl acetate copolymer, 89 parts by weight of an electrolyte obtained by dissolving LiPF ₆ in propylene carbonate at a concentration of 1 M / liter were added, followed by heating and mixing. Thus, a uniform paste was prepared. Preparation was performed under a nitrogen atmosphere. The paste was uniformly applied on a 200 μm-thick polyester film under an argon atmosphere. When gradually cooled to room temperature after coating, the coating liquid similarly lost its fluidity and formed an opaque gel-like film. When the thickness of this film was measured, it was 95 μm. The electrical conductivity of the sample at 25 ° C. of the solid electrolyte was 6.8 × 10 ⁻³ S / cm.

(Preparation of Secondary Battery) A thin-film type all solid secondary battery was assembled in the same manner as in Example 1 using the positive electrode, the negative electrode and the solid electrolyte membrane prepared as described above. Further, this secondary battery was subjected to a heat treatment in an oven at 80 ° C. for 5 minutes.

(Measurement of Discharge Capacity) A step of charging the above secondary battery at 4.05 V at 2.45 mA at room temperature (24 ° C.) and then discharging it to 2.0 V at 2.45 mA is defined as one cycle. And a discharge capacity at the fifth cycle was determined. The discharge capacity of this secondary battery was 50 mAh. The capacity retention of the battery was defined as the ratio of the discharge capacity after 30 cycles to the discharge capacity at the 5th cycle, and was found to be 84%.

(Evaluation of Adhesion Characteristics) The secondary battery after the discharge test was disassembled, and the adhesion between the positive electrode and the negative electrode and the solid electrolyte membrane was evaluated. Each layer is in close contact with each other,
No seepage of the solvent was observed.

[0072]

As described above, in the all solid state secondary battery of the present invention, the electrolyte layer is made of a gel organic polymer electrolyte, the positive electrode is made of a positive electrode active material and a gel organic polymer electrolyte, Since the negative electrode is composed of the negative electrode active material and the gel organic polymer electrolyte, the adhesion between the electrolyte layer and the positive electrode, the negative electrode is good, and even when the all-solid secondary battery of the present invention is used under severe conditions, Without causing the interfacial delamination,
A battery with extremely good cycle characteristics is obtained. Further, the all-solid-state secondary battery of the present invention is a secondary battery that has a very small interface impedance, a high capacity, and an excellent high-current discharge characteristic because of good bonding at the contact interface between the positive electrode and the negative electrode and the electrolyte layer. It has a great feature of becoming.

Further, the gel organic polymer electrolyte is
When the composition includes an organic polymer having a relative dielectric constant of 4 or more, an aprotic solvent, and an electrolyte salt, ion mobility in an all solid state secondary battery can be improved. Further, when the organic polymer is an acrylonitrile-based polymer, the acrylonitrile-based polymer has a high affinity for an aprotic solvent, so that it is easy to form a gel-like organic polymer electrolyte, and the affinity with an electrolyte salt is also high. Since it is high, a gel polymer having high ionic conductivity can be obtained, so that the capacity of the all-solid secondary battery can be further increased. When the acrylonitrile-based polymer is a (co) polymer containing 50 mol% or more of an acrylonitrile unit, the acrylonitrile-based polymer can maintain good solubility in an aprotic solvent and can be obtained. The ionic conductivity of the gelled solid electrolyte can be improved. Further, when the aprotic solvent is mainly composed of a carbonate-based solvent, the adhesion between the positive electrode or the negative electrode and the organic polymer electrolyte layer can be further improved, and the interlayer impedance further decreases. A secondary battery can be obtained.

[Brief description of the drawings]

FIG. 1 is a side sectional view of an all solid state secondary battery in an example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 3 Solid electrolyte membrane (electrolyte layer)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshihiko Hosako 20-1 Miyukicho, Otake City, Hiroshima Prefecture Mitsubishi Rayon Co., Ltd. Central Research Laboratory (72) Inventor Mitsuo Hamada 201-1 Miyukicho, Otake City, Hiroshima Prefecture No. 72 in Central Research Laboratory, Mitsubishi Rayon Co., Ltd. (72) Inventor Taiken Lab No. 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (72) Inventor Hiroyuki Akashi 6-7, Kita-Shinagawa, Shinagawa-ku, Tokyo No. 35 in Sony Corporation (72) Inventor Masahiro Aoki 6-7-35 Kita Shinagawa, Shinagawa-ku, Tokyo F-term in Sony Corporation (reference) 5H029 AJ03 AJ05 AJ06 AJ11 AJ12 AJ15 AK03 AK05 AL06 AL07 AL12 AM00 AM01 AM02 AM03 AM07 AM16 BJ04 DJ07 DJ09 DJ15 HJ07 HJ20

Claims (12)

[Claims] 1. An all-solid secondary battery having a structure in which an electrolyte layer made of a gel organic polymer electrolyte is inserted and fixed between a positive electrode and a negative electrode, wherein the positive electrode comprises a positive electrode active material and a gel organic An all-solid secondary battery comprising a polymer electrolyte, wherein the negative electrode comprises a negative electrode active material and a gel organic polymer electrolyte. 2. The gel organic polymer electrolyte according to claim 1, wherein the gel organic polymer electrolyte is a homogeneous composition having an organic polymer having a relative dielectric constant of 4 or more, an aprotic solvent, and an electrolyte salt. Solid secondary battery. 3. The all-solid secondary battery according to claim 2, wherein the organic polymer is an acrylonitrile-based polymer. 4. The acrylonitrile-based polymer contains at least 50 mol% of an acrylonitrile unit (co).
The all-solid secondary battery according to claim 3, which is a polymer. 5. The method according to claim 5, wherein the positive electrode is formed by forming a film of a composition including an acrylonitrile-based polymer, an aprotic solvent, an electrolyte salt, and a positive electrode active material into a gel, and the negative electrode is formed of acrylonitrile. The composition comprising a system polymer, an aprotic solvent, an electrolyte salt, and a negative electrode active material is formed into a film, and the composition is gelled. The method according to any one of claims 1 to 4, wherein All-solid rechargeable battery. 6. The positive electrode is obtained by forming a film of a composition comprising an acrylonitrile-based polymer, polyvinylidene fluoride, an aprotic solvent, an electrolyte salt, and a positive electrode active material, and gelling the composition. The negative electrode, an acrylonitrile-based polymer, polyvinylidene fluoride, an aprotic solvent, an electrolyte salt, and a film formed of a composition having a negative electrode active material, characterized in that it is gelled. The all-solid-state secondary battery according to claim 1. 7. The electrolyte layer comprises a composition having an acrylonitrile-based polymer, an aprotic solvent, and an electrolyte salt, or an acrylonitrile-based polymer, polyvinylidene fluoride, an aprotic solvent, and an electrolyte salt. 7. The all-solid secondary battery according to claim 1, wherein the composition having the following is a gelled composition. 8. The electrolyte layer is formed by impregnating any one of a woven fabric, a nonwoven fabric, and a paper-like material made of a fiber or a pulp-like material made of an acrylonitrile-based polymer with an aprotic solvent in which an electrolyte salt is dissolved. The all-solid secondary battery according to any one of claims 1 to 7, wherein the all-solid secondary battery is gelled. 9. The method according to claim 2, wherein the aprotic solvent contains a carbonate-based solvent.
9. The all-solid-state secondary battery according to any one of claims 8 to 8. 10. The all-solid secondary battery according to claim 1, wherein a current collector made of a metal thin film is provided on a surface of the positive electrode or the negative electrode. 11. The negative electrode according to claim 1, wherein a lithium metal or a lithium alloy is used instead of a negative electrode active material and a gel organic polymer electrolyte. All-solid rechargeable battery. 12. The woven fabric, nonwoven fabric or paper-like material constituting the electrolyte layer is a pulp-like material made of an acrylonitrile-based polymer, a fiber or a pulp-like material made of at least one kind of fiber and vinylidene fluoride or polyolefin. 9. The all-solid-state secondary battery according to claim 8, comprising a mixture with at least one of fibril-like substances.