JP6088896B2 - Manufacturing method of all solid state battery - Google Patents

Description

Since the binder can be degreased in a short time at a low temperature, the electrode active material or the solid electrolyte can be prevented from being deteriorated, and defects due to the binder remaining can be prevented, and an all-solid battery having excellent characteristics can be manufactured. The present invention relates to a method for manufacturing an all-solid battery that can be used. The present invention also relates to an all solid state battery using the method for producing the all solid state battery.

Most of the secondary batteries installed in portable electronic devices such as mobile phones and notebook computers are lithium secondary batteries. Lithium secondary batteries are expected to be put into practical use as large batteries for hybrid cars and power load leveling systems in the future, and their importance is increasing.

A lithium secondary battery is composed of a positive electrode and a negative electrode each containing a material capable of reversibly occluding and releasing lithium, an electrolyte in which a lithium ion conductor is dissolved in a non-aqueous organic solvent, and a separator. Yes. Among these, as the electrolytic solution, an electrolyte such as lithium perchlorate or lithium hexafluorophosphate dissolved in a solvent such as propylene carbonate is used.

However, a lithium secondary battery employing such a liquid electrolyte easily causes a short circuit between the positive electrode and the negative electrode due to the structure of the battery, and causes heat generation and ignition due to such a short circuit. There was a problem.

In order to solve these problems, safety is ensured by solidifying the electrolyte using a chemically stable polymer or inorganic ceramics in a wide potential window instead of a liquid electrolyte. The development of such a battery is under consideration. Among these, oxide ceramic solid electrolytes have high chemical stability and are attracting attention from the viewpoint of safety.

Ceramic-based solid electrolyte is formed by forming an inorganic fine particle dispersed paste composition in which inorganic fine particles such as ceramic powder and glass particles are dispersed in a binder resin into a green sheet, and a plate-like solid electrolyte is formed through a firing process. .
For example, Patent Document 1 discloses an active material slurry in which an active material is dispersed in a solvent containing a lithium ion conductive binder, and a solid in which a sulfide-based solid electrolyte is dispersed in a solvent containing a lithium ion conductive binder. After forming an active material sheet and a solid electrolyte sheet from the electrolyte slurry, the solid electrolyte sheet is sandwiched between two active material sheets, and further sandwiched between two current collector sheets to form a laminate and a binder A method of manufacturing a battery having a ceramic solid electrolyte by vacuum hot pressing at a temperature equal to or higher than the melting point of is described.

In addition, as a method for imparting mechanical strength to such an extent that a sheet such as an active material sheet or a solid electrolyte sheet is not torn at the time of cutting, laminating, pressing, etc., Patent Document 2 discloses a polyvinyl butyral resin as a binder resin. Is being studied.
However, in this method, in order to suppress the dislocation of the crystal structure of the Li-containing glass, a baking method for decomposing the binder resin by holding at 350 ° C. for 75 hours is performed, which is extremely inefficient. On the other hand, when the time is shortened in the firing step, the binder is not sufficiently decomposed, and there is a problem that conductive carbide remains in the electrolyte layer and self-discharge or internal short circuit occurs.

JP 2010-33918 A JP 2012-238545 A

In view of the above situation, the present invention is capable of degreasing the binder at a low temperature and in a short time. Therefore, the electrode active material or the solid electrolyte can be prevented from being deteriorated, and problems due to the binder remaining can be prevented. An all-solid battery manufacturing method capable of manufacturing an all-solid battery is provided. Moreover, the all-solid-state battery using the manufacturing method of this all-solid-state battery is provided.

The present invention relates to a method for producing an all-solid battery having an electrode active material layer and a solid electrolyte layer, wherein an electrode active material layer slurry containing an electrode active material and a binder for an electrode active material layer is formed to form an electrode active material. A step of producing a material sheet, a step of forming a solid electrolyte sheet slurry by forming a solid electrolyte and a solid electrolyte layer slurry containing a binder for the solid electrolyte layer, and laminating the electrode active material sheet and the solid electrolyte sheet step of preparing a, and has a firing step of firing the laminate at 400 ° C. below the temperature, the binder for the solid body electrolyte layer, the amount of hydroxyl groups is contained 23 mol% of a polyvinyl acetal resin, wherein Polyvinyl acetal resin has an α-olefin unit in the main chain, or a graft copolymerized unit composed of a methacrylic monomer. A polymer, in the firing step, a method for manufacturing an all-solid battery firing at 200 ° C. / min or more Atsushi Nobori rate.
Details will be described below.

As a result of intensive studies, the present inventors have determined that a polyvinyl acetal resin having a hydroxyl group content of 23 mol% or less is degreased before reaching 400 ° C. when heated at a temperature increase rate of 100 ° C./min or more in an inert gas atmosphere. Was found to end. And it discovered that a baking process could be completed in a short time by using such predetermined polyvinyl acetal resin for the slurry for electrode active material layers and / or the slurry for solid electrolyte layers, and came to complete this invention. .

In the present invention, first, a process for forming an electrode active material layer slurry by forming an electrode active material layer slurry containing an electrode active material and an electrode active material layer binder, and a solid electrolyte and a solid electrolyte layer binder are included. A step of forming a solid electrolyte sheet by forming a slurry for the solid electrolyte layer is performed.

The binder for an electrode active material layer and / or the binder for a solid electrolyte layer contains a polyvinyl acetal resin having a hydroxyl group content of 23 mol% or less.
Conventionally, in order to thermally decompose polyvinyl acetal resin at 400 ° C. or lower, it has been necessary to decompose over a long period of time. However, in the present invention, by using the polyvinyl acetal resin, the polyvinyl acetal resin at the time of thermal decomposition can be used. It becomes possible to suppress the generation of soot having many double bonds accompanying dehydration and decarboxylation reaction. As a result, the firing process can be completed in a short time even at a low temperature of 400 ° C.

In the polyvinyl acetal resin, the upper limit of the amount of hydroxyl groups is 23 mol%. By making the amount of the hydroxyl group 23 mol% or less, it becomes possible to leave a large amount of oxygen in the resin under a high temperature atmosphere, and degreasing in a short time becomes possible.
When the hydroxyl group content exceeds 23 mol%, the decomposition end temperature increases.
A preferable upper limit of the amount of the hydroxyl group is 18 mol%, and a preferable lower limit is 3 mol%. A more preferred upper limit is 16 mol%, a more preferred lower limit is 3 mol%, a still more preferred upper limit is 10 mol%, and a still more preferred lower limit is 4 mol%.

The degree of acetalization of the polyvinyl acetal resin is preferably 70 to 82 mol%.
If the degree of acetalization is less than 70 mol%, the amount of hydroxyl groups in the polyvinyl acetal resin increases, and the binder may not be decomposed under baking conditions of 400 ° C or lower. The acetalization degree of 82 mol% is the theoretical upper limit of the acetalization reaction. Preferably, it is 72-81 mol%.

Moreover, in the said polyvinyl acetal resin, it is preferable to reduce the amount of hydroxyl groups, but as the means, it is preferable to reduce the amount of hydroxyl groups by reactions other than acetalization.
The method for reducing the amount of hydroxyl groups by a reaction other than the acetalization is not particularly limited, and examples thereof include a method of reacting an epoxy compound and a hydroxyl group in the presence of an isocyanate compound, an acid, or a base.
Further, in the polyvinyl acetal resin, the functional group that is most likely to undergo hydrogen abstraction reaction is a hydroxyl group. Therefore, by utilizing this property, hydrogen abstraction reaction by heat or light of carbonyl compounds such as benzophenone, thermal decomposition of peroxide compounds. The amount of hydroxyl groups may be reduced using a hydrogen abstraction reaction (grafting reaction of a vinyl compound) or the like by radicals. Among these, grafting of a vinyl compound with a peroxide compound can be suitably used because the reaction itself is easy and various functional groups can be imparted.

The polyvinyl acetal resin is preferably obtained by acetalizing polyvinyl alcohol having a saponification degree of 80 mol% or more.
When polyvinyl alcohol having a saponification degree of less than 80 mol% is used, the acetalization reaction may be difficult because of the poor solubility of polyvinyl alcohol in water.

The polyvinyl alcohol preferably has a polymerization degree of 1000 to 4000.
When the polymerization degree is less than 1000, the strength of the electrode active material sheet or the solid electrolyte sheet may be insufficient. On the other hand, when the degree of polymerization exceeds 4000, the solubility in water may decrease, or the viscosity of the aqueous solution may become too high, making acetalization difficult. In addition, the solution viscosity becomes too high and the coatability is lowered. In the present invention, the degree of polymerization of polyvinyl acetal is the degree of polymerization of polyvinyl alcohol which is a raw material for synthesis. When mixing 2 or more types of polyvinyl alcohol, the average of these polymerization degrees is used.

The polyvinyl alcohol can be obtained by saponifying a vinyl ester polymer. Examples of the vinyl ester include vinyl formate, vinyl acetate, vinyl propionate, vinyl pivalate and the like, and vinyl acetate is preferable from the economical viewpoint.

The polyvinyl alcohol preferably contains an α-olefin in the main chain. Since the hydrogen bond strength of the polyvinyl acetal resin is weakened by the α-olefin, the viscosity stability over time can be improved, and the screen printability can be improved. Examples of the α-olefin include methylene, ethylene, propylene, isopropylene, butylene, isobutylene, pentylene, hexylene, cyclohexylene, cyclohexylethylene, and cyclohexylpropylene, and ethylene is particularly preferable. As content of the said alpha olefin, it is preferable that it is 1-20 mol%. If the amount is less than 1 mol%, the properties of the resulting polyvinyl acetal resin are the same as those of the unmodified polyvinyl acetal resin. If the amount is more than 20 mol%, the solubility of polyvinyl alcohol in water decreases. It becomes difficult or the hydrophobicity of the resulting polyvinyl acetal resin becomes too strong, so that the solubility in an organic solvent is lowered.

The polyvinyl alcohol may be copolymerized with other ethylenically unsaturated monomers as long as the effects of the present invention are not impaired. Examples of such ethylenically unsaturated monomers include acrylic acid, methacrylic acid, (anhydrous) phthalic acid, (anhydrous) maleic acid, (anhydrous) itaconic acid, acrylonitrile methacrylonitrile, acrylamide, methacrylamide, and trimethyl. -(3-acrylamido-3-dimethylpropyl) -ammonium chloride, acrylamido-2-methylpropanesulfonic acid and its sodium salt, ethyl vinyl ether, butyl vinyl ether, N-vinyl pyrrolidone, vinyl chloride, vinyl bromide, vinyl fluoride , Vinylidene chloride, vinylidene fluoride, tetrafluoroethylene, sodium vinyl sulfonate, sodium allyl sulfonate and the like. Also use terminal-modified polyvinyl alcohol obtained by copolymerizing vinyl ester monomer such as vinyl acetate with ethylene in the presence of thiol compounds such as thiol acetic acid and mercaptopropionic acid, and saponifying it. Can do.

The aldehyde used for the acetalization is not particularly limited. For example, formaldehyde (including paraformaldehyde), acetaldehyde (including paraacetaldehyde), propionaldehyde, butyraldehyde, amylaldehyde, hexylaldehyde, heptylaldehyde, 2-ethylhexylaldehyde Cyclohexyl aldehyde, furfural, glyoxal, glutaraldehyde, benzaldehyde, 2-methylbenzaldehyde, 3-methylbenzaldehyde, 4-methylbenzaldehyde, p-hydroxyaldehyde, m-hydroxyaldehyde, phenylacetaldehyde, phenylpropionaldehyde and the like. These aldehydes may be used alone or in combination of two or more, and acetaldehyde and / or butyraldehyde is preferably used.

The polyvinyl acetal resin is prepared by dissolving a polyvinyl alcohol resin in warm water, adding an aldehyde so as to have a predetermined degree of acetalization in the presence of an acid catalyst, reacting, and then washing, neutralizing, and drying. Can be obtained.

The acid catalyst is not particularly limited, and any organic acid or inorganic acid can be used. Examples thereof include acetic acid, paratoluenesulfonic acid, nitric acid, sulfuric acid, and hydrochloric acid. Moreover, as an alkali used for neutralization, sodium hydroxide, potassium hydroxide, ammonia, sodium acetate, sodium carbonate, sodium hydrogencarbonate, potassium carbonate etc. are mentioned, for example.

As a method for producing the polyvinyl acetal resin having a hydroxyl group content of 23 mol% or less, in addition to the method using the polyvinyl alcohol containing the α-olefin as a raw material, for example, a polyvinyl acetal resin produced under general production conditions And a method in which a monofunctional epoxy compound is reacted with the hydroxyl group, a method in which a thermally decomposable preferable methacrylic monomer is subjected to an addition reaction using a hydrogen abstraction radical initiator, and the like.
In the method of addition reaction of the methacrylic monomer, a graft copolymer obtained by graft-copolymerizing a unit composed of the methacrylic monomer to the hydroxyl group of the polyvinyl acetal resin before the reaction is obtained.

As said methacryl monomer, the methacryl monomer whose carbon number of an ester substituent is 4 or less is preferable, for example, methyl methacrylate, butyl methacrylate, isobutyl methacrylate, etc. are preferable.
Although it does not specifically limit as a radical initiator used for the said hydrogen abstraction, For example, perketal type, perester type | mold, a monocarbonate type, and a dialkyl type peroxide can be used preferably. As the peroxide used for hydrogen abstraction, a peroxide compound having a tert-butyl group, a phenyl group, a cumyl group, or the like can be preferably used because of its high hydrogen abstraction property.

Examples of the compound that undergoes an addition reaction with the hydroxyl group of the polyvinyl acetal resin include monomers such as acrylic monomer, styrene, α-methylstyrene, and vinyl acetate in addition to the methacrylic monomer. In particular, methacrylic monomers and acrylic monomers are preferable because thermal decomposability can be improved.

When the polyvinyl acetal resin is a graft copolymer, the degree of grafting is not particularly limited, but is 1 to 30 mol%. Within the above range, a polyvinyl acetal resin having a hydroxyl group content of 23 mol% or less can be produced without impairing the properties of the polyvinyl acetal resin. A more preferable degree of grafting is 5 to 20 mol%.
By using a polyvinyl acetal resin as a graft copolymer, a polyvinyl acetal resin having a hydroxyl group content of 18 mol% or less can be easily prepared.
The degree of grafting is the molar ratio of the graft chain portion.

As content of the said polyvinyl acetal resin in the said slurry for electrode active material layers, a preferable minimum is 1 weight% and a preferable upper limit is 20 weight%. If it is less than 1% by weight, an electrode active material sheet may not be formed. If it exceeds 20% by weight, the viscosity may be too high to obtain a smooth sheet.

As content of the said polyvinyl acetal resin in the said slurry for solid electrolyte layers, a preferable minimum is 3 weight% and a preferable upper limit is 10 weight%. If it is less than 3% by weight, the strength of the solid electrolyte layer sheet may be low and may not be handled. If it exceeds 10% by weight, residual carbon may remain without being defatted due to sinterability.

It is not particularly restricted but includes the electrode active material, for _{example, LiO 2 · Al 2 O 3} · SiO 2 type low melting point glass such as inorganic _{glass, Li 2 S-M x S} y (M = B, Si, Gc, P Lithium sulfur glass such as LiCoO ₂ , lithium manganese composite oxide such as LiMnO ₄ , lithium nickel composite oxide, lithium vanadium composite oxide, lithium zirconium composite oxide, lithium hafnium composite oxide , Lithium silicic acid phosphate (Li _3.5 Si _0.5 P _0.5 O ₄ ), lithium titanium phosphate (LiTi ₂ (PO ₄ ) ₃ ), lithium titanate (Li ₄ Ti ₅ O ₁₂ ), phosphoric acid germanium lithium _{(LiGe 2 (PO 4) 3} ), Li 2 O-SiO 2, Li 2 O-V 2 O 5 -SiO 2, _{i 2 O-P 2 O 5} -B 2 O 3, Li 2 O-GeO 2 Ba, Li 10 GeP 2 S 12 lithium oxide compounds such as, and the like. In addition, the average particle diameter of the electrode active material is preferably 0.05 to 50 μm.
Further, there is no clear distinction between the positive electrode active material and the negative electrode active material. For example, the positive and negative potentials are compared with the positive and the negative potentials when comparing the charge / discharge potentials of two kinds of compounds. When each is used, a battery having an arbitrary voltage can be formed.

It does not specifically limit as said solid electrolyte, You may use the same thing as the said electrode active material. Specifically, for example, low melting point glass such as LiO ₂ · Al ₂ O ₃ · SiO ₂ type inorganic glass, lithium sulfur type glass such as Li ₂ S-M _x S _y (M = B, Si, Gc, P). LiCoO ₂ , lithium cobalt composite oxide such as LiMnO ₄ , lithium manganese composite oxide such as LiMnO ₄ , lithium nickel composite oxide, lithium vanadium composite oxide, lithium zirconium composite oxide, lithium hafnium composite oxide, lithium silicate (Li _3.5 Si _0.5 P _0.5 O ₄ ), lithium titanium phosphate (LiTi ₂ (PO ₄ ) ₃ ), lithium titanate (Li ₄ Ti ₅ O ₁₂ ), lithium germanium phosphate (LiGe ₂ (PO _{4) 3), Li 2 O} -SiO 2, Li 2 O-V 2 O 5 -SiO 2, Li 2 O-P 2 O 5 -B 2 Examples thereof include lithium oxide compounds such as O ₃ , Li ₂ O—GeO ₂ Ba, and Li ₁₀ GeP ₂ S ₁₂ . The average particle size of the solid electrolyte is preferably 0.05 to 50 μm.

Although it does not specifically limit as content of the said electrode active material in the said slurry for electrode active material layers, A preferable minimum is 10 weight% and a preferable upper limit is 90 weight%. When the amount is less than 10% by weight, the viscosity may not be sufficiently obtained, and the coatability may be deteriorated. When the amount exceeds 90% by weight, it may be difficult to disperse the electrode active material. .

Although it does not specifically limit as content of the said solid electrolyte in the said slurry for solid electrolyte layers, A preferable minimum is 10 weight% and a preferable upper limit is 90 weight%. When the content is less than 10% by weight, the viscosity may not be sufficiently obtained and the coatability may be deteriorated. When the content exceeds 90% by weight, it is difficult to disperse the solid electrolyte. Sometimes.

Examples of the organic solvent used for the electrode active material layer slurry include ethylene glycol monobutyl ether, ethylene glycol monoethyl ether acetate, diethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoisobutyl ether, trimethylpentanediol monoisobutyrate, Examples thereof include butyl carbitol, butyl carbitol acetate, terpineol, terpineol acetate, dihydroterpineol, dihydroterpineol acetate, and texanol. In addition, these organic solvents may be used independently and may use 2 or more types together.

Examples of the organic solvent used in the solid electrolyte layer slurry include toluene, ethyl acetate, butyl acetate, ethanol, isopropanol, methyl isobutyl ketone, methyl ethyl ketone, methyl isobutyl ketone, ethylene glycol ethyl ether, isophorone, butyl lactate, and dioctyl. Examples include phthalate, dioctyl adipate, and benzyl alcohol. In addition, these organic solvents may be used independently and may use 2 or more types together.

In addition to the electrode active material, solid electrolyte, polyvinyl acetal resin, and solvent described above, the electrode active material layer slurry and the solid electrolyte layer slurry may include a flame retardant aid, a thickener, and an antifoam as necessary. Additives such as agents, leveling agents, and adhesion-imparting agents may be added.

The method for producing the slurry for the electrode active material layer and the slurry for the solid electrolyte is not particularly limited, and includes conventionally known methods. Each component is mixed using various mixers such as a ball mill, a bead mill, a blender mill, and a three roll. And the like.

The method for forming the electrode active material layer slurry to prepare an electrode active material sheet and the method for forming the solid electrolyte slurry to form a solid electrolyte sheet are not particularly limited. For example, one-side mold release treatment is performed. Examples of the method include coating on the applied support film, drying the organic solvent, and forming into a sheet.

The support film is preferably a resin film having heat resistance and solvent resistance and flexibility. Since the support film has flexibility, the slurry can be applied to the surface of the support film by a roll coater, a blade coater, etc., and the obtained sheet can be stored and supplied in a rolled state. it can.

Examples of the material for the support film include polyethylene terephthalate, polyester, polyethylene, polypropylene, polystyrene, polyimide, polyvinyl alcohol, polyvinyl chloride, polyfluoroethylene, and other fluorine-containing resins, nylon, and cellulose.
As for the thickness of the said support film, 20-100 micrometers is preferable, for example.
Moreover, it is preferable that the surface of the support film is subjected to a release treatment, whereby the support film can be easily peeled off.

Next, in the present invention, a step of laminating the electrode active material sheet and the solid electrolyte sheet to produce a laminate is performed.
Examples of the method of laminating include a method of forming a sheet and then performing thermocompression bonding by heat pressing, heat laminating, and the like.

Next, in the present invention, a firing process is performed in which the laminate is fired at a temperature of 400 ° C. or lower in an inert gas atmosphere.
In the present invention, firing at a low temperature of 400 ° C. or lower can be realized by using the polyvinyl acetal resin.
In the firing step, when the heating temperature exceeds 400 ° C., the Li-containing glass used for the solid electrolyte may be thermally deteriorated.
In addition, the preferable minimum of heating temperature is 350 degreeC, and a preferable upper limit is 380 degreeC.

In the firing step, firing is preferably performed at a temperature increase rate of 200 ° C./min or more. Thereby, the dehydration and decarboxylation reaction of the binder resin can be suppressed, and there is an advantage that it can be decomposed at 400 ° C. or less by leaving oxygen in the resin.
Preferably it is 200-1000 degrees C / min.
Moreover, the one where baking time is shorter is preferable.
The all solid state battery obtained by using the method for producing an all solid state battery of the present invention is also one aspect of the present invention.

According to the present invention, since the binder can be degreased at a low temperature and in a short time, the electrode active material or the solid electrolyte can be prevented from being deteriorated, and problems due to the residual binder can be prevented, and the all-solid battery having excellent characteristics. The manufacturing method of the all-solid-state battery which can be manufactured can be provided. Moreover, the all-solid-state battery using the manufacturing method of this all-solid-state battery can be provided.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

(Synthesis Example 1)
(Synthesis of polyvinyl acetal resin)
230 g of polyvinyl alcohol having a polymerization degree of 1000, a saponification degree of 98 mol%, and an ethylene content of 6 mol% was added to 2900 g of pure water, and stirred at a temperature of 90 ° C. for about 2 hours for dissolution. This solution is cooled to 40 ° C., 80 g of hydrochloric acid having a concentration of 35% by weight and 165 g of n-butyraldehyde are added thereto, the temperature of the solution is lowered to 15 ° C., and this temperature is maintained to perform an acetalization reaction. The product was precipitated. Thereafter, the liquid temperature was maintained at 50 ° C. for 3 hours to complete the reaction, and neutralized, washed with water and dried by a conventional method to obtain a white powder of polyvinyl acetal resin. The obtained polyvinyl acetal resin was dissolved in DMSO-d ₆ (dimethyl sulfoxide), and the degree of acetalization was measured using ¹³ C-NMR (nuclear magnetic resonance spectrum). The degree of acetalization was 72 mol%. Yes, the amount of hydroxyl groups was 20 mol%.

(Synthesis Example 2)
230 g of polyvinyl alcohol having a polymerization degree of 1700 and a saponification degree of 98 mol% was added to 2900 g of pure water, and stirred at a temperature of 90 ° C. for about 2 hours for dissolution. This solution is cooled to 40 ° C., 20 g of hydrochloric acid having a concentration of 35% by weight and 145 g of n-butyraldehyde are added thereto, the temperature of the solution is lowered to 15 ° C., and this temperature is maintained to carry out an acetalization reaction. The product was precipitated. Thereafter, the liquid temperature was kept at 40 ° C. for 3 hours to complete the reaction, and neutralized, washed with water and dried by a conventional method to obtain a white powder of polyvinyl acetal resin. When the obtained polyvinyl acetal resin was dissolved in DMSO-d ₆ (dimethyl sulfoxide) and the degree of acetalization was measured using ¹³ C-NMR (nuclear magnetic resonance spectrum), the degree of acetalization was 78 mol%. there were.

200 g of the obtained polyvinyl acetal resin was weighed and added together with 400 g of methyl isobutyl ketone to a 2 L separable flask equipped with a stirrer, a cooler, a thermometer, a hot water bath, and a nitrogen gas inlet, and then stirred at 80 ° C. And dissolved until transparent and uniform.
Next, 20 g of perbutyl O (manufactured by NOF Corporation) as a graft reaction initiator was added to the polyvinyl acetal solution layer at 80 ° C. After 3 minutes, 50 g of isobutyl methacrylate was added dropwise to the polyvinyl acetal solution at 80 ° C. with a dropping funnel to cause a graft reaction. ^{When the} degree of grafting was measured using ¹³ C-NMR (nuclear magnetic resonance spectrum), it was 10 mol%, and the amount of hydroxyl groups was 10 mol%.

Example 1
(1) Preparation of slurry for solid electrolyte To 10 parts by weight of the polyvinyl acetal resin obtained in Synthesis Example 1, 90 parts by weight of methyl isobutyl ketone was added and dissolved. Next, 50 parts by weight of LiS—P ₂ S ₅ glass (average particle diameter of 2.0 μm) as a solid electrolyte glass is added to 10 parts by weight of polyvinyl acetal resin, kneaded with a high-speed stirrer, and a slurry for solid electrolyte. Got.

(2) Production of Solid Electrolyte Sheet Using a blade coater on a support film (width 400 mm, length 30 m, thickness 38 μm) made of polyethylene terephthalate (PET), in which the obtained slurry for solid electrolyte was previously subjected to mold release treatment The applied coating was dried at 80 ° C. for 30 minutes to remove the solvent, and a 250 μm thick coating layer was formed on the support film to produce a solid electrolyte sheet.

(3) Preparation of positive electrode and negative electrode sheet Solid electrolyte slurry in which 30 parts by weight of lithium vanadium phosphate as a negative electrode active material, 3 parts by weight of conductive carbon (acetylene black) and 10 parts by weight of n-propanol as an additional solvent were prepared in advance. The slurry for negative electrode active material layers was prepared.
The obtained slurry for negative electrode active material layer was applied onto a release PET film by blade coating, dried at 80 ° C. for 30 minutes, and then released from the release PET film to obtain a negative electrode active material sheet. It was. In addition, the slurry for negative electrode active material layers was apply | coated so that the thickness of a negative electrode active material sheet might be set to 60 micrometers.
Moreover, the positive electrode active material sheet was produced similarly to the negative electrode active material sheet. In addition, the slurry for positive electrode active material layers was apply | coated so that the thickness of a positive electrode active material layer might be 30 micrometers.

(4) Production of laminate
After peeling off the PET film from the solid electrolyte sheet, it was sandwiched between the negative electrode active material sheet and the positive electrode active material sheet and thermocompression bonded at 80 ° C. and 10 kN for 60 seconds to prepare a laminate.
Next, an external electrode paste made of terpineol, silver, low-melting glass, and acrylic resin was applied to a stainless steel plate with a doctor blade to a thickness of 500 μm, and both surfaces of the laminate were adhered to form a current collector.

(5) Laminate degreasing calcined tubular furnace AMF-N (Asahi Rika Seisakusho Co., Ltd.) is set in the center, the obtained laminate is set, and nitrogen gas is sent at 20 mL / min, while the temperature rises 200 ° C./min The speed was increased to 350 ° C. Next, after heating up to 400 degreeC and hold | maintaining at 400 degreeC for 20 minutes, the heater was turned off and the inside of a furnace was cooled with nitrogen gas. When the inside of the furnace became 100 ° C. or lower, the battery was taken out to obtain an all solid state battery.

(Example 2)
An all-solid battery was produced in the same manner as in Example 1 except that the polyvinyl acetal resin obtained in Synthesis Example 2 was used instead of the polyvinyl acetal resin obtained in Synthesis Example 1.

(Comparative Example 1)
An all-solid battery was produced in the same manner as in Example 1 except that polyvinyl butyral resin (BM-2, manufactured by Sekisui Chemical Co., Ltd., hydroxyl amount 31 mol%) was used instead of the polyvinyl acetal resin obtained in Synthesis Example 1. did.
In addition, degreasing baking of the laminated body was performed by putting the laminated body into a muffle furnace, raising the temperature to 600 ° C. at a temperature rising rate of 10 ° C./min in a nitrogen atmosphere, holding the resultant for 1 hour, and then cooling.

<Evaluation>
The following evaluation was performed about the all-solid-state battery obtained by the Example and the comparative example. The results are shown in Table 1.

(1) Constant current charge / discharge evaluation By using a charge / discharge evaluation apparatus TOSCAT-3000 (manufactured by Toyo System Co., Ltd.), the obtained all-solid-state battery is charged at 200 mA up to 4V, and after resting for 1 hour, it is discharged by 3V. The constant current charging / discharging evaluation was performed and the following criteria were evaluated.
The case where the charge / discharge curve was obtained was indicated by “◯”, and the case where the discharge curve was not obtained for some reason such as a short circuit was indicated by “x”.

(2) Residual carbon evaluation The solid electrolyte sheets prepared in Examples 1 and 2 and Comparative Example 1 were baked in an electric furnace at 450 ° C. for 30 minutes. Residual carbon (ppm) was measured using a carbon sulfur analyzer (Horiba Seisakusho).
When the residual carbon was less than 200 ppm, “◯” was given, and when it was 200 ppm or more, “x” was given.

According to the present invention, since the binder can be degreased at a low temperature and in a short time, the electrode active material or the solid electrolyte can be prevented from being deteriorated, and problems due to the residual binder can be prevented, and the all-solid battery having excellent characteristics. The manufacturing method of the all-solid-state battery which can be manufactured can be provided. Moreover, the all-solid-state battery using the manufacturing method of this all-solid-state battery can be provided.

Claims (3)

A method for producing an all-solid battery having an electrode active material layer and a solid electrolyte layer,
Forming an electrode active material sheet by forming an electrode active material layer slurry containing an electrode active material and an electrode active material layer binder;
Forming a solid electrolyte sheet by molding a solid electrolyte layer slurry containing a solid electrolyte and a solid electrolyte layer binder;
Laminating the electrode active material sheet and the solid electrolyte sheet to produce a laminate, and
Having a firing step of firing the laminate at a temperature of 400 ° C. or lower;
The solid body electrolyte layer binder has a hydroxyl amount contained 23 mol% of a polyvinyl acetal resin,
The polyvinyl acetal resin has a α-olefin unit in the main chain, or is a graft copolymer obtained by graft copolymerization of a unit composed of a methacryl monomer,
In the baking step, baking is performed at a temperature rising rate of 200 ° C./min or more.
Method for manufacturing an all-solid battery, wherein the this. The method for producing an all-solid-state battery according to claim 1, wherein the polyvinyl acetal resin has an α-olefin unit content of 1 to 20 mol%. The method for producing an all-solid-state battery according to claim 1, wherein the methacrylic monomer is a methacrylic monomer having an ester substituent having 4 or less carbon atoms.