JPH11288738A - Solid electrolytic battery and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and inexpensively realize high mechanical strength, high thermal stability, low interfacial resistance, and high ion conductivity, in a solid electrolytic battery. SOLUTION: On the surface opposed to a solid electrolyte layer having chemical bridged parts respectively carried by a positive electrode and a negative electrode, an adhering electrolyte layer bridging them each other is provided. Construction materials of the adhering electrolyte layer are preferably a vinylidene fluoride skeleton, an acrylonitrile skeleton, and an acrylic skeleton included in its high polymer matrix. The adhering electrolyte layer is formed by holding its raw material liquid by at least one surface of the solid electrolyte layer of the positive electrode side or the negative electrode side, and by gelatinizing the raw material liquid by natural-cooling, heating, or irradiation of energy rays such as light or electron rays, etc. Gelation under the condition that the raw material liquid is impregnated into a separator is also possible. Thus, the high-performance lithium secondary battery is constituted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid electrolyte battery, and more particularly to a solid electrolyte battery having sufficient mechanical strength, thermal stability, low interface resistance,
The present invention relates to a high-performance solid electrolyte battery having both high ionic conductivity and a simple manufacturing method thereof.

[0002]

2. Description of the Related Art With the rapid progress of miniaturization, thinning, and lightening of electronic devices, batteries supporting these electric powers are also required to be reduced in size and increased in energy density. Non-aqueous water containing light metals such as lithium and magnesium as the negative electrode active material and carbon fluoride, copper oxide, manganese dioxide, lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), etc. as the positive electrode active material Electrolyte batteries are known as batteries that can meet such demands. Many non-aqueous electrolyte batteries use an electrolyte obtained by dissolving an electrolyte salt in an organic solvent so as not to react with the light metal. However, as long as the liquid is used, there is a concern that the electrolyte may leak or the inside of the battery may be dried due to the volatilization of the organic solvent. This causes an increase in internal impedance or an internal short circuit.

As a battery capable of solving these disadvantages, a solid electrolyte battery has been proposed. This battery typically uses a polymer electrolyte in which an inorganic salt is dissolved in a polymer matrix composed of an oxyethylene chain or an oxypropylene chain. However, although this solid solution is excellent in processability and freedom of molding, its ionic conductivity at room temperature is on the order of 10 ^-5 S / cm, which is superior to ordinary non-aqueous electrolyte, because it is a perfect solid. About three orders of magnitude lower. For this reason, various devices for improving the ionic conductivity of the solid electrolyte battery have been conventionally devised. For example, an example is known in which the ionic conductivity is improved to the order of 10 ⁻⁴ S / cm by making the skeleton structure of the polymer matrix into a dendritic structure.

Japanese Patent Application Laid-Open No. 54-104541 discloses a method in which a polymethyl methacrylate powder is dissolved in an organic electrolyte by heating or a polymerization initiator is added to an organic electrolyte in which a polymethyl methacrylate monomer is dissolved. The disclosed semi-solid (gel) organic electrolyte is disclosed. The ionic conductivity of these organic electrolytes is on the order of 10 ^-4 S / cm.

JP-A-63-94501 discloses a method for producing an ion-conductive solid electrolyte in which a liquid composition containing an acryloyl-modified polyalkylene oxide and a salt of an inorganic ion is cured by irradiating it with ultraviolet light or visible light. It has been disclosed. The ionic conductivity of the organic electrolyte obtained by this method is on the order of 10 ^-4 to 10 ^-8 S / cm.

Further, in US Pat. No. 5,607,485, a xerogel is obtained by removing a solvent from a gel-like substance obtained by dissolving a polymer in an organic electrolytic solution, and the xerogel is again dissolved in the solvent or the electrolyte. A method is disclosed in which an electrolyte containing a salt is permeated and gelled again. In actual production of the battery, the xerogel is formed on the surface of each of the positive electrode and the negative electrode, and then the xerogels are heat-pressed to each other. In this state, the electrolyte containing the solvent or the electrolyte salt is permeated again. Many of the polymers used here are linear thermoplastic polymers that are soluble in the organic electrolyte, and can be easily heat-sealed by raising the temperature to near the melting point during thermocompression bonding. Therefore, the interface between the xerogels on both electrodes can be almost completely eliminated, and the gel regenerated from the xerogel also has the interface eliminated. Therefore, the interface resistance can be reduced, and as a result, a decrease in ionic conductivity can be suppressed.

[0007]

However, there are still many problems to be solved in the prior art. First, the gel organic electrolyte described in JP-A-54-104541 described above is relatively easy to produce, but has insufficient mechanical strength. This is because a part of the cross-linking point is constituted by a physically cross-linked portion of a polymer. Here, the physical bridge portion has a small binding energy of about the thermal kinetic energy,
It is a cross-linking portion that repeats generation / disappearance due to increase and decrease in molecular motion. In the above-mentioned organic electrolyte, the thermal motion of the polymer increases in a high temperature range, the physical cross-linking portion decreases, and the solubility increases, so that the mechanical strength decreases. The reduction of the physical cross-links causes loss of the properties as a solid electrolyte and, in some cases, progresses the state change from gel to sol.

[0008] When the solid state is deteriorated in this way, there is a danger that a battery without a separator may cause a short circuit between the positive and negative electrodes, which is dangerous. Also, when the temperature inside the battery rises and the strength, viscoelasticity and low diffusivity of the solid electrolyte deteriorate, it becomes difficult to pass the nail penetration test and the crush test of the battery. Note that the above solification is intentionally generated when the solid electrolyte formed on the positive electrode and the solid electrolyte formed on the negative electrode are integrated by heating and pressing during the production of the solid electrolyte battery. , Lower interfacial resistance at the junction,
In addition, it can be considered to be useful for suppressing a decrease in ionic conductivity. However, at the stage of thermocompression bonding, since the nonaqueous electrolyte is still contained in the solid electrolyte layer, it is actually difficult to perform sufficient heating to cause gelation, and a remarkable effect cannot be expected.

On the other hand, Japanese Unexamined Patent Publication No.
According to the method described in JP-A No. 1 (KOKAI), a solid electrolyte excellent in both mechanical strength and heat resistance can be obtained. This is because a part of the crosslinking points is constituted by a chemically crosslinked portion.
Here, the chemical cross-linking portion is a cross-linking portion formed by a covalent bond that is not extinguished by energy of the degree of thermal motion of a molecule.
Therefore, the above-mentioned solid electrolyte is useful for improving the reliability of the battery, and is particularly useful as an electrolyte layer for a secondary battery in which repetitive charge / discharge characteristics are important.

However, when such a solid electrolyte is applied to the actual production of a battery, a liquid composition containing a polymer is thinly applied to the surface of each of the positive electrode and the negative electrode, and the coated film is irradiated with light. Because of the necessity, the solvent easily evaporates from the surface of the coating film. In addition, since the surface of the solid electrolyte is always present at the solid-gas interface during the formation process, a difference occurs in the physical properties between the surface portion and the deep portion of the solid electrolyte layer, and the ionic conductivity of the surface layer generally decreases. Furthermore, the solid electrolyte layer formed on each of the positive electrode and the negative electrode has a chemically stable surface, so that even when pressed, the surfaces of the solid electrolyte only contact macroscopically, and a clear joint is formed. There is an interface. For this reason, the interface impedance increases, and the ionic conductivity greatly decreases.

The solid electrolyte described in US Pat. No. 5,607,485 has good ionic conductivity because the interface between the positive and negative electrodes is almost inconspicuous as described above. In that regard,
This is the same as the organic electrolyte described in Japanese Patent No. 104541, and has the same problems.

As described above, the conventional solid electrolyte using the polymer matrix simultaneously satisfies all of mechanical strength, thermal stability, low interface resistance, and high ionic conductivity which are sufficient as a material constituting a battery. It was not something you could do. Accordingly, an object of the present invention is to provide a high-performance solid electrolyte battery using a solid electrolyte that simultaneously satisfies these various characteristics, and a simple manufacturing method thereof.

[0013]

Means for Solving the Problems The present inventors have conducted studies to achieve the above-mentioned object, and as a result, the solid electrolyte layers formed on the surfaces of the positive electrode and the negative electrode have been constituted by a chemically crosslinked portion. It has been found that it is preferable to use a solid to be used, and that it is preferable to interpose a solid electrolyte layer for adhesion that bridges these solid electrolyte layers on the joint surface of each other, and have come to propose the present invention. . In other words, even if the stable surfaces of the solid electrolyte layers having the chemical cross-linking portions are pressed together as they are, only macro contact can be achieved, so that a solid electrolyte layer for adhesion capable of cross-linking both is newly provided, The molecular chains are entangled on the surfaces of both solid electrolyte layers to obscure the interface and achieve micro contact. With the obscuration of the interface, the interface impedance can be reduced, and the ionic conductivity can be increased. In addition, since the solid electrolyte layers formed on the surfaces of the positive electrode and the negative electrode have a chemically crosslinked portion, they do not basically exhibit thermoplastic behavior and have excellent thermal stability and mechanical strength. Can be provided.

In particular, if the solid electrolyte layer for adhesion is mainly composed of a chemically crosslinked portion, the solid electrolyte layer included in the solid electrolyte battery of the present invention has a positive electrode holding portion, a negative electrode holding portion, All of the contact portions between the two have a chemically crosslinked portion. For this reason, the thermal reliability can be greatly improved as compared with the case where the solid electrolyte layer for adhesion having only the physical cross-linking portion is used. Also,
The positive electrode holding portion, the negative electrode holding portion, or a configuration in which at least one of the solid electrolyte layers of the contact portion is supported on a separator, or by including dispersed particles, more than expected from the inherent viscoelasticity of the polymer matrix A solid electrolyte layer having high strength can be obtained. Thereby, a solid electrolyte battery having high resistance to mechanical external force can be configured.

It is particularly preferable to use, as the above-mentioned solid electrolyte layer for adhesion, one in which at least a part of the polymer matrix contains at least one of a vinylidene fluoride skeleton and an acrylonitrile skeleton in order to enhance thermal reliability. . This is because those containing a vinylidene fluoride skeleton have a high softening point and therefore hardly exhibit thermoplastic behavior even in a high temperature range, and those containing an acrylonitrile skeleton show thermosetting behavior due to a cyclization reaction.

In addition, the use of a solid electrolyte layer constituting at least one of the positive electrode holding portion, the negative electrode holding portion, and the contact portion, which has an acrylic skeleton in at least a part of its polymer matrix, requires a high ionic conductivity. It is particularly suitable for increasing viscoelasticity. This is because the solubility parameter of a polymer having an acrylate group is similar to that of many organic solvents generally used in electrolytes of non-aqueous batteries, and the interaction between the polymer skeleton and the solvent is extremely large. In addition, it is possible to achieve a value of 1 × 10 ⁻³ S / cm or more, which is comparable to that of a solvent, as the ionic conductivity required for the reactions of the positive and negative electrodes. Further, a polymer containing an acrylic skeleton can easily increase the number of chemically crosslinked portions by introducing a polyfunctional monomer, and is advantageous in improving the viscoelasticity and thermal stability of the solid electrolyte.

In addition, when an ethylene oxide group is introduced into the acrylic skeleton, a solid electrolyte having an ion conductivity as excellent as a liquid electrolyte is obtained. Ethylene oxide is a component of polyethylene oxide which is considered to have the best properties as a solid electrolyte at the present time.
It is believed that the ability to have a cyclic four-coordinate structure with respect to i ^{+ and the} high degree of freedom of movement of the molecular chain itself contribute to its excellent properties. Moreover, since the basic skeleton is an acrylic skeleton, the strong interaction with the solvent derived from the acrylic skeleton itself and the strong interaction with the electrolyte salt derived from the ethylene oxide group promote the ionization of the electrolyte salt. And increase the transit rate.

To produce the solid electrolyte battery of the present invention,
First, a solid electrolyte layer having a chemically crosslinked portion is formed on at least the surfaces of the positive electrode active material layer of the positive electrode and the negative electrode active material layer of the negative electrode in the first step, and then the polymer material or the polymerizable material is formed in the second step. The raw material liquid containing at least one of the compounds is held on at least one surface of the solid electrolyte layer on the positive electrode side or the negative electrode side, and then the solid electrolyte layers on the positive electrode side and the negative electrode side are opposed to each other in a third step. As described above, the positive electrode and the negative electrode are laminated, and the raw material liquid is gelled in a fourth step.

Here, as the method of gelation, at least one of natural cooling, heating or energy ray irradiation is performed according to the composition of the raw material liquid. In these methods, since the gelation is performed in a state where the raw material liquid is held between the solid electrolyte layers on the positive electrode side and the negative electrode side in advance, the manufacturing process after forming the solid electrolyte layer for adhesion is simplified, Manufacturing costs can be reduced. Gelation by spontaneous cooling is a method that can increase the ionic conductivity of the contact portion while maintaining the thermal stability of the solid electrolyte layers on the positive electrode side and the negative electrode side already formed. In addition, in the gelation process, the polymer chains having a large degree of freedom of movement in the raw material liquid are entangled with the polymer matrix of the solid electrolyte layer in the positive and negative electrode portions, and the crosslinking reaction proceeds. Can reduce the interface impedance with the solid electrolyte layer.

The gelation by heating can form a chemically cross-linked portion uniformly if the temperature is maintained at a constant temperature for a predetermined time or more. In addition, the "positive electrode / solid electrolyte layer / raw material liquid / solid electrolyte layer / negative electrode" This method can be performed in a state in which the laminate is accommodated in an outer container of a battery, so that the method is extremely excellent in manufacturing efficiency. Gelation by energy beam irradiation is a method that can increase the ionic conductivity of the adhered portion while maintaining the thermal stability of the already formed solid electrolyte layers on the positive electrode side and the negative electrode side. Since the irradiation of the raw material liquid at this time is performed while being held between the solid electrolyte layers, a physical property gradient in the layer due to evaporation of the solvent from the surface of the coating film is less likely to occur.

In the second step, when the separator impregnated with the raw material liquid is placed on the surface of the solid electrolyte layer, the formed solid electrolyte layer for adhesion is carried on the separator. Therefore, it is possible to obtain a solid electrolyte layer for adhesion having a higher strength than expected from the inherent viscoelasticity of the polymer matrix of the solid electrolyte layer, and it is possible to increase the resistance of the solid electrolyte battery to mechanical external force. In addition, since the shape of the final solid electrolyte layer for adhesion is also determined by the shape of the separator used, there is also an effect of simplifying the manufacturing process. Any of the above-described methods for forming the solid electrolyte layer for adhesion can be applied to the formation of the solid electrolyte layer on the positive electrode side or the solid electrolyte layer on the negative electrode side.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, two types of solid electrolyte layers are used: a solid electrolyte layer held on the positive electrode side and the negative electrode side, and a solid electrolyte layer for adhesion interposed between these opposing surfaces. . These are all homogeneous viscoelastic materials containing a polymer material, a non-aqueous solvent, and an electrolyte salt. Therefore, it is excellent in ionic conductivity, high-temperature stability, easy processability, low creep property, and adhesiveness, and also excellent in liquid retention and shape retention even though it contains a large amount of non-aqueous electrolyte. The solid electrolyte layer held on the positive electrode side and the negative electrode side mainly has a chemical cross-linking portion, but the solid electrolyte layer for adhesion has a chemical cross-linking portion mainly, or has a physical cross-linking portion. It may be mainly possessed. Hereinafter, the solid electrolyte layer having a chemically crosslinked portion and the solid electrolyte layer having a physically crosslinked portion will be separately described.

First, the solid electrolyte layer having a physically crosslinked portion will be described. Examples of the polymer constituting the polymer matrix of the solid electrolyte layer having a physically crosslinked portion include epoxy resins such as polyethylene oxide and polypropylene oxide, polyvinylidene fluoride, polyvinylidene fluoride and hexafluoropropylene (HFP) or tetrafluoropropylene. It is composed of a linear polymer such as a binary copolymer or terpolymer with propylene (TFP), polyacrylonitrile, polyurethane, polysiloxane, polyphosphazene, polyacrylate, and Nafion. Alternatively, it may have an epoxy skeleton, a urethane skeleton, or an acrylic skeleton as a part or a side chain of the main chain composed of these linear polymers. Further, a part of the side chain may contain a functional group such as a sulfone group, a carbonyl group, and an imide group.

The solid electrolyte layer having these physical cross-linking portions can be formed by allowing a coating film of a raw material liquid containing a polymer material in a dissolved state to be cooled and gelled. When such a solid electrolyte layer is used for adhesion to the opposing surfaces of the solid electrolyte layers held by the positive electrode and the negative electrode, a clear interface does not occur, so that a decrease in ionic conductivity is minimized. Can be.

Next, the solid electrolyte layer having a chemically crosslinked portion will be described. Examples of the polymer constituting the polymer matrix of the solid electrolyte layer having a chemically crosslinked portion include linear polymers such as polyethylene oxide, polypropylene oxide, polyvinylidene fluoride, polyacrylonitrile, polyurethane, polysiloxane, polyphosphazene, and polyacrylate. A polymer in which a chemically crosslinked portion is introduced into a part of the polymer is used. Here, a urethane skeleton, an acrylic skeleton, and an epoxy skeleton are exemplified as the chemical cross-linking portion. Examples of such a polymer include a polysiloxane having an ethylene oxide chain in a side chain and an acrylic resin having an ethylene oxide chain in a side chain or a main chain.

In the present invention, as a method of forming a solid electrolyte layer having a chemically crosslinked portion, a coating film of a raw material liquid containing a polymerizable compound is heated or irradiated with energy rays to gel the coating film. . In addition, the gelation referred to here is
It includes both a polymerization reaction and a crosslinking reaction. The polymerizable compound is a compound containing a hetero atom other than a carbon atom, such as an oxygen atom, a nitrogen atom, and a sulfur atom, in the molecule. It is considered that the hetero atom contributes to the improvement of the ion conductivity through the promotion of ionization of the electrolyte salt in the solid electrolyte layer, and also has a function of improving the strength of the solid electrolyte. The polymerizable compound is not limited to a monomer, and may be a prepolymer or a mixture of a monomer and a prepolymer.

Gelation by heating can be carried out, for example, in a mixed system of a polymer material and an organic peroxide.
That is, a radical generated by the cleavage of the organic peroxide abstracts a hydrogen atom from the polymer to generate a polymer radical, and the crosslinking between polymer chains mainly proceeds. By this mechanism, many polymer materials can be crosslinked at a temperature of 80 ° C. or higher, preferably 120 ° C. or higher without having a special functional group. As the organic peroxide, a compound generally known as a thermal polymerization initiator, such as dicumyl peroxide and benzoyl peroxide, can be used.

Alternatively, when a rubber-based polymer such as a diene-based polymer is used, a vulcanization accelerator such as 2-mercaptobenzothiazole or dithiocarbamate may be added to obtain a polymer.
C., preferably at about 140 ° C. In addition, cross-linking using formate azide is also possible. In addition, crosslinking using one or more functional groups such as a carbon-carbon double bond, a hydroxyl group, a carboxyl group, an imino group, and an amino group is also possible. Some of these proceed at room temperature, such as an addition reaction to a carbon-carbon double bond.

Polymerization and crosslinking by irradiation with energy rays include the following. First, gelation by light is effective for a mixed system of polyvinyl alcohol and cinnamic acid chloride, a polymer having an azide-type functional group, and a photoresist generally used in semiconductor production. If a polymerization initiator is used in combination, a polymer having a vinyl group can also be used as a raw material. Regarding gelation by radiation, many polymers, such as polymers having a polyvinylidene fluoride, ethylene, or ester skeleton, can be crosslinked by γ-irradiation. In addition, an electron beam, X
Lines can also be used. In the gelation by energy beam irradiation, it is necessary to pay attention to the irradiation energy distribution so that the chemically crosslinked portion is formed uniformly.

These various polymerization reactions and cross-linking reactions may be employed alone or in combination of two or more. In general, the above-mentioned gelation is preferably performed in an inert gas atmosphere, and a solid electrolyte layer having excellent ionic conductivity and mechanical strength can be formed as compared with the case where the gelation is performed in the air.

The general characteristics of the solid electrolyte layer having a chemically crosslinked portion formed in the present invention are generally as follows. The elastic modulus is, for example, 10 ⁶ dyn / cm ² or less when measured using a dynamic viscoelasticity tester. The preferred range of the elastic modulus in the present invention is 10 ² to 10 ⁵ dyn /.
cm ² , more preferably 10 ³ to 10 ⁵ dyn
/ Cm ² . The elongation is 20% or more. Those having the largest elongation percentage do not break up to about 400% and have a resilience to stretching deformation. Also, 180 °
Does not break when bent. Regarding the creep characteristic, even if the strain amount is measured by using, for example, a creep meter, the strain amount is so low that it hardly changes over time.

The liquid retention is a level at which the electrolyte contained therein does not leak even when the solid electrolyte is compressed with a load of 25 g / cm ² using the creep meter.
The ionic conductivity measured by the AC impedance method at 25 ° C. does not exceed a value specific to the non-aqueous electrolyte contained in the solid electrolyte layer, but is generally about 1
The order of × 10 ^-2 to 1 × 10 ^-4 S / cm is maintained.
That is, a decrease in the value due to solidification is minimized.

By the way, in the present invention, even if the solid electrolyte layer has either a chemically crosslinked portion or a physically crosslinked portion, excellent characteristics can be obtained when the polymer matrix is composed of an acrylic resin. be able to. Such a solid electrolyte layer can be formed using a monofunctional or polyfunctional (meth) acrylate monomer, prepolymer, or polymer. Hereinafter, these compounds will be described in detail. In the present specification, the term “(meth) acrylate” refers to both acrylate and methacrylate.

First, monofunctional (meth) acrylates include alkyl (meth) acrylates such as methyl (meth) acrylate, butyl (meth) acrylate, and trifluoroethyl (meth) acrylate; alicyclic (meth) acrylate; Hydroxyalkyl (meth) acrylates such as ethyl acrylate and hydroxypropyl acrylate; preferably having 1 to 4 carbon atoms, such as hydroxypolyoxyethylene (meth) acrylate and hydroxypolyoxypropylene (meth) acrylate
A hydroxypolyoxyalkylene (meth) acrylate having an oxyalkylene group, such as methoxyethyl acrylate, ethoxyethyl acrylate, and phenoxyethyl acrylate; and an alkoxyalkyl (meth) acrylate having an alkoxy group having preferably 1 to 4 carbon atoms. .

In addition, methyl ethylene glycol (meth) acrylate, ethyl ethylene glycol (meth) acrylate, propyl ethylene glycol (meth) acrylate, phenyl ethylene glycol acrylate, ethoxyethylene glycol acrylate, methoxyethyl acrylate, methoxydiethylene glycol methacrylate, Alkyl ethylene glycol (meth) acrylates such as methoxytriethylene glycol (meth) acrylate and methoxytetraethylene glycol methacrylate; and ethyl propylene glycol acrylate, butyl propylene glycol acrylate, and methoxy propylene glycol acrylate.

Further, the (meth) acrylate may contain a heterocyclic group. The heterocyclic group is a heterocyclic residue containing a hetero atom such as an oxygen atom, a nitrogen atom, and a sulfur atom. The type of the heterocyclic group contained in the (meth) acrylate is not particularly limited, and examples thereof include a furfuryl group and a tetrahydrofurfuryl group. Examples of the (meth) acrylate derivative having a furfuryl group include furfuryl (meth) acrylate, furfurylethylene glycol (meth) acrylate, and furfurylpropylene glycol (meth) acrylate, and a (meth) acrylate derivative having a tetrahydrofurfuryl group Examples thereof include tetrahydrofurfuryl (meth) acrylate, tetrahydrofurfuryl ethylene glycol (meth) acrylate, and tetrahydrofurfuryl propylene glycol (meth) acrylate.

The molecular weight of the above-mentioned monofunctional (meth) acrylate and its prepolymer is usually less than 500, preferably 300 or less. In the case of a (meth) acrylate having a molecular weight of 500 or more, the non-aqueous electrolyte is easily leached from the obtained solid electrolyte layer. The above (meth) acrylate may be used alone, or two or more kinds may be used in combination. The proportion of the (meth) acrylate in the raw material liquid of the solid electrolyte layer is 50% by weight or less, preferably 5 to 40% by weight, more preferably 10 to 30% by weight, based on the nonaqueous electrolyte. Within the range.

Examples of the bifunctional (meth) acrylate include ethylene glycol dimethacrylate, diethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, and butanediol di (meth) acrylate.
Acrylate, triethylene glycol di (meth) acrylate, and tripropylene glycol diacrylate are exemplified. Examples of the trifunctional (meth) acrylate include trimethylolpropane tri (meth) acrylate, ethylene oxide-modified trimethylolpropane triacrylate, and polyolefin-modified trimethylolpropane triacrylate. These trifunctional (meth) acrylates can achieve excellent liquid retention, ionic conductivity, and mechanical strength when a solid electrolyte layer is formed, and are the most preferable. More polyfunctional (meta)
Examples of the acrylate include pentaerythritol penta (meth) acrylate and dipentaerythritol hexa (meth) acrylate.

When these monofunctional (meth) acrylates and polyfunctional (meth) acrylates are used in combination, the amount of the polyfunctional (meth) acrylate added is 4 to the amount of the non-aqueous electrolyte.
% By weight, preferably in the range of 0.05 to 2% by weight. In particular, when a trifunctional (meth) acrylate is used, the ionic conductivity and the ionic conductivity can be reduced by a small amount of 2% by weight or less, preferably 0.05 to 0.5% by weight, based on the nonaqueous electrolyte. A solid electrolyte layer having extremely excellent mechanical strength can be obtained. In addition, as the polymerizable compound used in the present invention, a mixed system of a polyene and a polythiol may also be used.

When a monomer or a prepolymer is used, a photopolymerization initiator or a thermal polymerization initiator may be added to the raw material liquid. Examples of the photopolymerization initiator include a carbonyl compound group. These compounds include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether,
Benzoins such as benzoin isobutyl ether and α-phenyl benzoin; and anthraquinones such as anthraquinone, methylanthraquinone and chloroanthraquinone, as well as benzyl, diacetyl, acetophenone, benzophenone and methylbenzoyl formate. In addition, sulfur-containing compounds such as diphenyl sulfide and dithiocarbamate; halides of fused ring hydrocarbons such as α-chloromethylnaphthalene; pigments such as acrylflavin and fluorescein; metal salts such as iron chloride and silver chloride; Onium salts such as -methoxybenzenediazonium, hexafluorophosphoric acid, diphenyliodonium, triphenylsulfonium and the like can be exemplified. These may be used alone or in combination of two or more. Particularly preferred are carbonyl compounds, sulfur compounds and onium salts.

As the thermal polymerization initiator, bis- (4-t-
In addition to peroxydicarbonates such as (butylcyclohexyl) peroxydicarbonate and diisopropylperoxydicarbonate, azobisisobutyronitrile, benzoyl peroxide and lauroyl peroxide can be mentioned. Dimethylaniline, cobalt naphthenate, sulfinic acid, and mercaptan may be used as other polymerization initiators. These polymerization initiators can be used in combination with the aforementioned photopolymerization initiator and thermal polymerization initiator. The amount of these polymerization initiators used is in the range of 0.1 to 10% by weight, preferably 0.5 to 7% by weight, based on all (meth) acrylates. However, by performing the process continuously,
When residual radicals are present in the solid electrolyte layer on the positive electrode side or the negative electrode side, chain polymerization is performed without adding a polymerization initiator to the monomer or prepolymer contained in the raw material liquid in contact with the solid electrolyte layer. It is possible to start the reaction.

A sensitizer and a storage stabilizer can be further added to the raw material liquid for the solid electrolyte layer, if necessary. Examples of the sensitizer include a nitrile compound such as N, N-di-p-aminobenzonitrile, a phosphorus compound such as tri-n-butylphosphine, and urea. The addition amount of the sensitizer is in the range of about 0.1 to 5 parts by weight based on 100 parts by weight of all (meth) acrylate. As the storage stabilizer, quaternary ammonium chloride, benzothiazole, and hydroquinone can be used. The addition amount of the storage stabilizer is also in the range of about 0.1 to 5 parts by weight based on 100 parts by weight of the total (meth) acrylate.

The raw material liquid for the solid electrolyte layer of the present invention contains a non-aqueous electrolyte. This non-aqueous electrolyte is obtained by dissolving an electrolyte salt in a non-aqueous solvent. The concentration of the electrolyte salt in the non-aqueous electrolyte is usually 1.0 to 7.0 mol / l,
Preferably, it is in the range of 1.0 to 5.0 mol / liter. If it is less than 1.0 mol / liter, it becomes difficult to form a solid electrolyte layer having sufficient mechanical strength, and
When the amount exceeds mol / liter, it becomes difficult to dissolve the electrolyte salt.

The amount of the nonaqueous electrolyte used is usually 200% by weight or more, preferably 400 to 900% by weight, based on the amount of the monomer, prepolymer or polymer used as the raw material for forming the polymer matrix of the solid electrolyte layer. Particularly preferably, it is in the range of 500 to 800% by weight. If it is less than 200% by weight, a sufficiently high ionic conductivity cannot be achieved, and if it exceeds 900% by weight, it is difficult to solidify the non-aqueous electrolyte. In particular, when (meth) acrylate is used as a raw material for forming a polymer matrix, it is important to optimize both the concentrations of the electrolyte salt and the (meth) acrylate in the non-aqueous electrolyte. That is, when the concentration of the electrolyte salt is around the lower limit of 1.0 mol / liter, the concentration of (meth) acrylate is required to be 20 to 50% by weight to solidify the non-aqueous electrolyte. On the other hand, in a high concentration region where the concentration of the electrolyte salt is 1.5 mol / liter or more,
Even when the concentration of the (meth) acrylate is 10 to 20% by weight, a solid electrolyte layer having sufficiently excellent characteristics can be formed.

As the electrolyte salt, the following general formula (I) LiXFn... (I) (where X is any one of B, P, As and Sb atoms, and when X is B atom, n = 4 and n = 6 when X is any one of a P atom, an As atom and an Sb atom), or the following general formula (II) LiX (RSO ₂ ) n ... (II) (where X is any one of an N atom, a C atom, a B atom, or a C atom having an alkyl side chain, R is a methyl group or an ethyl group, and n is an integer of 1 to 3) The representative is a sulfonate represented by the following formula: Specific examples of the Lewis acid double salt include LiBF ₄ , LiAsF ₆ , Li
There are PF ₆ and LiSbF ₆ . Specific examples of the sulfonate include LiCF ₃ SO ₃ and LiN (CF ₃
SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiC (CH
₃ ) (CF ₃ SO ₂ ) ₂ .

As another electrolyte salt, LiCl
O ₄ , LiCF ₃ CO ₃ , NaClO ₃ , NaBF ₄ ,
NaSCN, KBF ₄ , Mg (ClO ₄ ) ₂ , Mg (B
F ₄ ) ₂ . The above-mentioned sulfonate has corrosiveness, and particularly when aluminum is used for the positive electrode current collector, the corrosion may be remarkable. In such a case, adding a Lewis acid double salt to the sulfonate or further adding the other electrolyte salt described above is effective in suppressing corrosion.

The use of an ester solvent is preferable because the ionic conductivity and elastic modulus of the obtained solid electrolyte can be improved. In addition to the above carbonate-based solvents, γ
-Butyrolactone, sulfolane, dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,2-dimethoxyethane, 1,2-
Ethoxymethoxyethane or glymes such as methyl glyme, methyl triglyme, methyl tetraglyme, ethyl glyme, ethyl diglyme, butyl diglyme can be used.

By the way, the above solid electrolyte layer is combined with a positive electrode having a positive electrode active material and a negative electrode having a negative electrode active material to form a solid electrolyte battery. Particularly, when the battery is a lithium battery or a lithium ion battery, it exhibits extremely good characteristics. The positive electrode active material is roughly classified into an inorganic material and an organic material. Examples of the inorganic material include TiS ₂ , MoS ₂ , Co ₂ S ₆ , FeS ₂ , and Nb.
Transition metal chalcogen compounds such as S ₂ , ZrS ₂ and VSe ₂ ; transition metal oxides such as V ₂ O ₅ , MnO ₂ and CoO ₂ ; LiCoO ₂ , LiNiO ₂ , LiFeO ₂ and Li
Lithium-containing composite oxides such as Mn ₂ O ₄ ; or Co, Ni, Fe, Mn in these lithium-containing composite oxides
LiCoX in which part of is further replaced by another element X
O ₂ , LiNiXO ₂ , LiFeXO ₂ , LiMn ₂ X
O ₄ can be mentioned. Among these, lithium-containing composite oxides have become the mainstream of recent positive electrode active materials because of their high potential and high energy, and are synthesized by firing high-temperature starting materials such as carbonates, hydroxides, and nitrates. Is used.

Although inorganic materials generally have a high volume energy density, rapid charge / discharge is difficult due to the slow diffusion rate of cations in the electrode, and the reversibility to overdischarge is poor. Many have room.
In addition, mechanical strength of the inorganic material is not so high because it is necessary to press-mold the inorganic material using a binder such as tetrafluoroethylene resin powder at the time of manufacturing the electrode. Another problem is that if lithium ions are excessively accumulated during overdischarge, the crystal structure is destroyed and the function as a secondary battery is impaired.

On the other hand, as the organic material, one-dimensional graphite, carbon fluoride, graphite, and a conductive polymer can be used. Examples of the conductive polymer include polyaniline, polypyrrole, polyazulene, polyphenylene, polyacetylene, polyphthalocyanine, poly-3-methylthiophene, polypyridine, polydiphenylbenzidine, and derivatives thereof. In any case, a material having an electric conductivity of 1 × 10 ⁻² S / cm ² or more, showing high cycle characteristics even at a discharge depth of 100%, and being relatively resistant to overdischarge as compared with inorganic materials. It is preferable to select The conductive polymer has the advantage of being excellent in moldability and processability as compared with inorganic materials, but has a low volume energy density due to a low density of the active material, and an excessive amount of electrolyte salt in the non-aqueous electrolyte. It costs. In addition, since the change in the concentration of the nonaqueous electrolyte due to the charge / discharge reaction is large and the change in the liquid resistance is large, there is a problem that an excessive amount of the nonaqueous electrolyte is required to smoothly advance the charge / discharge reaction. These are disadvantageous in improving the energy density.

As described above, since both inorganic and organic materials have advantages and disadvantages, it is also effective to form a composite of the two. For example, when a conductive polymer having an electric conductivity of 1 × 10 ⁻² S / cm or more and a transition metal oxide are kneaded to form a positive electrode, the conductive polymer is a binder, an active material, and a current collector. It has three functions of the body. In addition, since the conductive polymer is insulated at a low potential, even when the positive electrode is in an overdischarged state, the conductive polymer is insulated so that the inorganic active material contained therein is more than necessary. This prevents accumulation of lithium ions and prevents the crystal structure of the inorganic active material from being destroyed. This makes it possible to form a positive electrode that is resistant to overdischarge. As such a conductive polymer, polyacetylene,
Resix active materials such as polypyrrole, polythiophene, polyaniline, and polydiphenylbenzidine are suitable, and a remarkable effect is particularly observed in nitrogen-containing compounds.
As the inorganic active material, those having excellent potential flatness are preferable, and examples thereof include oxides of transition metals such as V, Co, and Ni, and composite oxides of these transition metals and alkali metals.

In order to produce a positive electrode using these positive electrode active materials, the positive electrode active material may be added in a solvent such as dimethylformamide, N-methylpyrrolidone, tetrahydrofuran or the like, if necessary, with a binder, a conductive agent and the like. It is most common to mix and disperse with the additives to prepare a high-concentration positive electrode paint, apply the positive-electrode paint on the current collector, and then dry it. In this case, the dispersion of the positive electrode active material is performed using a device such as a roll mill, a ball mill, and a valence mill. The application of the positive electrode paint is performed using a wire bar or a blade coater, or by a spray method.

As the binder, it is required that the binder has excellent resistance to an electrolytic solution and high mechanical strength for maintaining an electrode film on the premise that the characteristics of the positive electrode active material are not impaired. For example, Teflon, polyethylene, nitrile rubber, polybutadiene, butyl rubber, polystyrene,
Styrene-butadiene rubber, nitrocellulose, cyanoethylcellulose, polyacrylonitrile, polyvinyl fluoride, polyvinyl acetate, polyvinylidene fluoride, polyethylene, polystyrene, polypropylene, polytetrafluoroethylene, polymethyl methacrylate, polychloroprene, polyvinyl pyridine and the like. . Further, as the conductive agent, any material may be used as long as it is an electron conductive material that does not cause a chemical change in the configured battery system, and a commonly used material such as natural graphite and artificial graphite can be used. .

As the current collector, for example, a metal such as copper, stainless steel, gold, platinum, nickel, aluminum, molybdenum, titanium or the like, formed into a sheet, foil, mesh, punched metal, expanded metal or the like, Alternatively, a mesh or nonwoven fabric made of a fiber obtained by compounding these metals by plating, vapor deposition, kneading, or the like may be used. These can be similarly used as a positive electrode current collector described later.
Among them, copper, aluminum, and stainless steel are advantageous from the viewpoint of electrical conductivity, chemical stability, electrochemical stability, economy, workability, etc., and further, from the viewpoint of lightness and electrochemical stability. Copper and aluminum are particularly preferred.

The surface of the current collector is more preferably roughened. By performing the surface roughening, the contact area with the active material layer is increased, the adhesion is improved, and an effect of lowering the impedance as a battery can be expected. In the preparation of an electrode using an active material paint, the adhesion between the active material and the current collector can be significantly improved by performing a surface roughening treatment. Examples of the surface roughening method include polishing using emery paper, blasting, and chemical or electrochemical etching. Blasting is suitable for roughening the surface of the stainless steel current collector, but etching is most suitable for the aluminum current collector. This is because, because aluminum is a soft metal, the current collector itself is deformed before roughening is performed in blasting. If it is an etching treatment, the μ can be obtained without causing deformation or a significant decrease in strength of the aluminum current collector.
The surface can be effectively roughened on the order of m.

On the other hand, as the negative electrode active material, not only natural graphite but also a carbon material obtained as a fired body of a carbon-based material such as graphite, pitch coke, synthetic polymer and natural polymer is preferable. Specifically, the fired body is (1) an insulating or semiconductive carbon material obtained by firing a natural polymer or a synthetic polymer such as phenol or polyimide in a reducing atmosphere at 400 to 800 ° C. )coal·
800-130 pitch synthetic polymer or natural polymer
Conductive carbon material obtained by firing in a reducing atmosphere at 0 ° C., (3) conductive carbon material obtained by firing coke, pitch, synthetic polymer, and natural polymer in a reducing atmosphere of 2000 ° C. or more Material. Among them, carbon material and natural graphite obtained by firing mesophase pitch and coke under a reducing atmosphere of 2500 ° C. or more have excellent potential flatness,
It also has favorable electrode characteristics.

The carbon anode as described above can be formed into a sheet. Examples of a method for producing the negative electrode at this time include a method in which a carbon material sheet is directly formed on a current collector by a wet papermaking method using a dispersion liquid in which a carbon material is dispersed together with a suitable binder, followed by drying. There is a method of pressing a carbon material sheet formed on a support by a wet papermaking method onto a current collector, or a method of applying a negative electrode coating material containing a carbon material and a binder on the current collector and drying it. As the binder and the current collector, those used at the time of manufacturing the positive electrode can be used.

In the case of a solid electrolyte battery, it is possible to provide the solid electrolyte layer with a function as a separator. However, the electrolyte between the electrodes is made uniform, the mechanical strength is improved, and the reliability of the manufactured battery is improved. In order to improve the quality, it is effective to integrate the separator with the separator. In particular, such consideration is necessary for a secondary battery. As the separator, a separator that has low resistance to ion migration of the electrolyte layer and has excellent electrolyte retention is used.
For example, nonwoven fabrics and woven fabrics made of fibers such as glass, polyester, Teflon, polyflon, and polypropylene alone or in combination are exemplified.

In the present invention, both the solid electrolyte layers on the positive electrode side and the negative electrode side and the solid electrolyte layer for adhesion interposed therebetween are formed on the electrode, the separator, or the active material layer. Can be formed directly. That is, the raw material liquid of the solid electrolyte layer is applied or impregnated to the battery elements such as the electrodes and the separator, and is naturally cooled, heated, and converted into a viscoelastic body by a gelling means such as energy irradiation, so that the solid electrolyte layer is formed. At this point, this is integrated with each battery element. When a separator is used, the electrode that is first integrated with the separator during the manufacturing process may be either a positive electrode, a negative electrode, or both. In addition, using a wound body or a laminate in which the separator is sandwiched between a positive electrode and a negative electrode, non-aqueous electrolyte secondary batteries of various forms such as a cylindrical type, a coin type, a gum type, and a flat type are manufactured. However, this form is not particularly limited.

Further, mixing the dispersed particles into at least one of the solid electrolyte layers on the positive electrode side and the negative electrode side, and the solid electrolyte layer for adhesion interposed therebetween, can also improve the strength and strength of the solid electrolyte battery of the present invention. It is effective in increasing thermal stability. As dispersed particles, glass, inorganic oxide,
Inorganic nitride, inorganic sulfide, inorganic carbide, metal, alloy, polyester, tetrafluoroethylene, polyfluorocarbon, polypropylene, particles made of each material such as polyethylene,
Alternatively, composite particles in which glass or another inorganic substance is mixed with or coated with an organic polymer material can be used.

[0061]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described. The cell used for the measurement of ionic conductivity was formed by forming a solid electrolyte layer having a thickness of 1 mm on the surface of each of two discs made of SUS steel or Li having a diameter of 20 mm by a casting method, instead of electrodes. The solid electrolyte layer for adhesion was formed while keeping the gap between both electrodes constant. The AC impedance was measured at 25 ° C. using one disk of the measurement cell as a working electrode and the other disk as a reference electrode. In addition, since the measurement of the elastic modulus of the solid electrolyte layer for adhesion is difficult to perform in the form of the measurement cell as described above, a bulk measurement sample using the same material is separately prepared, and a dynamic viscoelasticity test is performed. Machine (made by Rheology Co .; Model name: MR-30
0 solid liquid meter). Regarding the high-temperature stability of the solid electrolyte layer for adhesion, a bulk measurement sample was allowed to stand at 150 ° C. for 30 minutes in a sealed state to suppress volatilization of the solvent, and the change in gel shape was relatively evaluated.

The non-aqueous solvents and electrolyte salts used in the following examples are all battery-grade specimens that have been sufficiently purified to have a water content of 20 ppm or less. The preparation of the measurement cell and the bulk measurement sample and the various measurements were all performed in an argon atmosphere.

Next, the formation of the solid electrolyte layer will be described. First, the basic non-aqueous electrolyte is LiN (CH) in a solvent in which propylene carbonate, ethylene carbonate, and dimethyl carbonate are mixed at a volume ratio of 2: 3: 5.
₃ SO ₂ ) ₂ was prepared by dissolving to a concentration of 1.8 mol / l. This is used as a raw material liquid A.

Next, based on the above-mentioned electrolyte solution A, the following material solutions B to I were prepared as the material solutions to be gelled.
The composition of each raw material liquid and its gelling method will be sequentially described. [Raw material liquid B] ・ Raw material liquid A 20 parts by weight ・ Trifunctional polyethylene glycol (average molecular weight: about 1,000, ethylene oxide group / hydroxyl group = about 7.0) 5 parts by weight ・ Hexamethylene diisocyanate 1 part by weight It was prepared by mixing and stirring the above materials. Gelation can be performed, for example, by heating at 70 ° C. for 24 hours in an Ar atmosphere.

[Material liquid C] 10 parts by weight of material liquid A 3 parts by weight of polymethyl methacrylate Material liquid C was prepared by mixing and stirring the above materials at 70 ° C. for 3 hours. Gelation can be performed, for example, by allowing the mixture to cool at room temperature for 2 hours in an Ar atmosphere.

[Raw material liquid D] 5 parts by weight of raw material liquid A 1 part by weight of polyethylene oxide acrylate Triethylamine copper (sensitizer) A catalytic amount based on the photosensitive group However, the above polyethylene oxide acrylate is polyethylene oxide triol (average) Molecular weight ≒ 300
0) 10 parts by weight of pyridine and 1.16 parts by weight of pyridine
0 parts by weight, and a solution in which 1.96 parts by weight of acrylic acid chloride was dissolved in 20 parts by weight of benzene was dropped in an Ar gas atmosphere, and the solution was reacted for 6 hours to synthesize. Gelation can be performed, for example, by using a high-pressure mercury lamp with a cold mirror and irradiating with light at 50 mW / cm ² for 2 minutes.

[Raw material liquid E] 5 parts by weight of raw material liquid A 1 part by weight of methyl methacrylate 0.01 parts by weight of benzoyl peroxide The raw material liquid E was prepared by mixing and stirring the above materials. Gelation can be performed, for example, by using a high-pressure mercury lamp with a cold mirror and irradiating with light at 50 mW / cm ² for 10 minutes. Alternatively, for example, 70 ° C., 24
Time heating may be performed.

[Raw material liquid F] ・ 5 parts by weight of raw material liquid A ・ 1 part by weight of vinylidene fluoride-hexafluoropropylene copolymer (trade name: FLEX2750, manufactured by Atochem Japan Co., Ltd.) It was prepared by mixing and stirring for 3 hours. Gelation can be performed, for example, by allowing the mixture to cool at room temperature for 2 hours in an Ar atmosphere.

[Raw material liquid G] 7 parts by weight of raw material liquid A 1 part by weight of polyacrylonitrile (average molecular weight: 150,000) The raw material liquid G was prepared by mixing and stirring the above materials at 60 ° C. for 3 hours. Gelation can be performed, for example, by allowing the mixture to cool at room temperature for 2 hours in an Ar atmosphere.

[Raw material liquid H] ・ Raw material liquid A 86 parts by weight ・ Methyl methacrylate (monofunctional monomer) 13.7 parts by weight ・ Ethylene oxide-modified trimethylolpropane triacrylate (polyfunctional monomer 0.3 parts by weight ・ benzoin isopropyl ether ( (Polymerization initiator) 0.05 parts by weight The raw material liquid H was prepared by mixing and stirring the above materials, and the gelation was possible by light irradiation at 80 mW / cm ² for 1 minute using a high-pressure mercury lamp with a cold mirror, for example. It is.

[Raw material liquid I]-86 parts by weight of material liquid A-13.7 parts by weight of methyl methacrylate (monofunctional monomer)-ethylene oxide-modified trimethylolpropane triacrylate (0.3 parts by weight of polyfunctional monomer-benzoin isopropyl ether ( Polymerization initiator) 0.05 parts by weight ・ Benzyl carbodiimide 0.14 parts by weight Gelation can be performed by heating at 60 ° C. for 3 hours in an Ar atmosphere, for example.

Examples 1 to 10 and Comparative Examples 1 to Ratio
Comparative Example 2 The electrode plate used in these examples was a SUS plate. For the preparation of the solid electrolyte layer on the electrode plate, and the solid electrolyte layer at the contact portion, the above-described raw material liquids B to I are appropriately selected to prepare a measurement cell and a bulk measurement sample, respectively. Each item of conductivity, elastic modulus, high temperature stability, and process easiness was evaluated. The type of the raw material liquid used for producing each solid electrolyte layer and the evaluation results are shown in the list of FIG. The criteria for the evaluation of ionic conductivity, elastic modulus, high temperature stability, and process easiness are as follows. [Ion conductivity]…: 1.2 × 10 ^-3 S / cm or more ○: 0.6 × 10 ^-3 S / cm or more, 1.2 × 10 ^-3 S / cm
Less than cm △ ... 0.3 × 10 ^-3 S / cm or more, 0.6 × 10 ^-3 S / cm
Less than cm × ... less than 0.3 × 10 ⁻³ S / cm [Elastic modulus]…: 1 × 10 ³ dyn / cm ² or more ○… 1 × 10 ² dyn / cm ² or more, 1 × 10 ³ dyn
Less than / cm ² △ ... less than 1 × 10 ² dyn / cm ² [high-temperature stability]…: no change at 80 ° C. (for rapid change in elastic modulus) ○: slight change at 80 ° C. (Same as above) Δ: Change at 80 ° C is recognized (Same as above) ×: Large change at 80 ° C (Same as above) [Ease of process] ◎: Very good ○: Good △: Normal

Examples 1 and 2 are measuring cells in which the solid electrolyte layers on both electrodes are in close contact with the solid electrolyte layers mainly composed of physical crosslinked portions. Although the ionic conductivity was slightly improved as compared with No. 2, the high-temperature stability was slightly lowered as compared with the conventional product. In all of Examples 3 to 12, the ionic conductivity was significantly improved as compared with the comparative example, and the same results as those of the comparative example were obtained with respect to the elastic modulus, high-temperature stability and processability. However, in Example 6, in which the separator was impregnated with the solid electrolyte layer in the contact portion, the measurement of the elastic modulus was not possible, but a remarkable improvement in high-temperature stability was observed. Examples 9 and 10 provided particularly excellent results in all evaluation items. These two embodiments are common in that either the solid electrolyte layer on the electrode or the solid electrolyte layer at the contact portion contains an acrylic skeleton and an ethylene oxide group.

Examples 11 to 20 and Comparative Examples 3 to
Comparative Example 4 Next, in order to evaluate the performance as an actual battery, a button-type lithium secondary battery for evaluation was produced by the following procedure.
First, a positive electrode was produced as follows. 3 parts by weight of polyvinylidene fluoride are dissolved in 38 parts by weight of N-methylpyrrolidone, 50 parts by weight of LiCoO ₂ as a positive electrode active material and 9 parts by weight of graphite as a conductive agent are added, and mixed and dispersed in an inert atmosphere using a homogenizer. Then, a positive electrode paint was prepared. The thickness of this positive electrode paint is 20 μm in air using a wire bar.
And dried at 125 ° C. for 30 minutes to obtain a positive electrode having a positive electrode active material layer having a thickness of 40 μm and a total thickness of 60 μm. On this positive electrode, a raw material liquid excluding the polymer material from the raw material liquids used in Examples 1 to 10 and Comparative Examples 1 and 2 was applied. As one counter electrode, Examples 1 to 1
A 200 μm-thick Li plate was used instead of one of the SUS plates in Comparative Examples 1 and 2. The positive electrode and the counter electrode were crimped to produce a lithium secondary battery.

A charge / discharge cycle test was performed on each of the batteries produced in Examples 11 to 20 and Comparative Examples 3 and 4. The test was performed using a charge / discharge measurement device (Hokuto Denko; model name HJ
-201B) was used. One cycle of the measurement is as follows: “Charging to a battery voltage of 4.2 V at a current density of 0.33 mA / cm ² →
1 hour rest → discharge to a battery voltage of 3.0 V at a current density of 0.33 mA / cm ² → 1 hour rest ”. Here, the discharge capacity (mAh) at the time of (1/3) C discharge in the fifth cycle was evaluated as the initial discharge capacity. In the fifth cycle (1 /
3) The ratio (%) of the discharge capacity at the 1C discharge in the sixth cycle to the discharge capacity at the C discharge was evaluated as a current load characteristic. Further, the ratio (%) of the discharge capacity at the 50th cycle to the initial discharge capacity was evaluated as an initial capacity change rate.

FIG. 2 shows the results. From this, Example 11
In each of Examples 20 to 20, the initial capacity is improved to about 2.0 to 5.6 times and the current load characteristics are improved to about 1.5 to 7.0 times as compared with Comparative Examples 3 and 4. I understood that. In particular, in Examples 19 and 20, excellent results were obtained in all the evaluation items. That is, it was confirmed that the solid electrolyte layer which exhibited the excellent properties in the above-described Examples 1 to 10 provided excellent charge / discharge characteristics even when incorporated in an actual battery.

Although the present invention has been described based on the twenty embodiments, the present invention is not limited to these embodiments. For example, in Examples 11 to 20 described above, button-type lithium secondary batteries for evaluation were manufactured, but the present invention can be widely applied to solid electrolyte batteries other than these, and not only secondary batteries but also It can also be applied to primary batteries. In addition, the type and formation method of the solid electrolyte of the contact portion, material selection of the positive electrode active material, the counter electrode active material and the non-aqueous electrolyte, and details of the form of the battery to be produced are within the scope of the present invention. Select, change,
Combinations are possible.

[0078]

As is apparent from the above description, in the present invention, the solid electrolyte layers having the chemically cross-linked portions formed on each of the positive electrode and the negative electrode are opposed to each other with the solid electrolyte layer for adhesion therebetween. Thereby, the ionic conductivity and the mechanical strength of the solid electrolyte battery can be improved. By forming the solid electrolyte layer for adhesion as a layer mainly composed of a chemically crosslinked portion, thermal stability is further improved. Further, forming a composite of a separator and dispersed particles on the solid electrolyte layer on the electrode or in the contact portion contributes to further improvement in thermal stability and mechanical strength. Adopting a vinylidene fluoride skeleton or acrylonitrile skeleton for at least a part of the polymer matrix of the solid electrolyte layer for adhesion is effective in increasing thermal reliability, and adopting an acrylic skeleton is
This is effective in achieving high ionic conductivity and viscoelasticity at low cost. When an ethylene oxide group is introduced into the acrylic skeleton, the ionic conductivity can be significantly improved.

In the solid electrolyte battery of the present invention, the raw material liquid for the solid electrolyte layer for adhesion is held on at least one surface of the solid electrolyte layer formed on each of the positive electrode and the negative electrode. According to the method for producing, it can be produced with extremely excellent production efficiency. Gelation is
The progress can be made extremely easily by at least one of natural cooling, heating, and energy beam irradiation. In the case where a separator is used, gelation can be performed in a state where the raw material liquid is impregnated in the separator, which facilitates production.

[Brief description of the drawings]

FIG. 1 shows the ionic conductivity, elastic modulus, high-temperature stability, and process of a solid electrolyte layer for measurement cells and bulk measurement samples prepared in Examples 1 to 10 and Comparative Examples 1 and 2. It is the chart which summarized the evaluation result of easiness.

FIG. 2 is a table summarizing the results of a charge / discharge cycle test of the button-type lithium secondary batteries for evaluation produced in Examples 11 to 20 and Comparative Examples 3 and 4.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Toshige Fujii 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company, Ltd.

Claims (12)

[Claims] 1. A positive electrode comprising a solid electrolyte layer having a chemically crosslinked portion held on at least a surface of a positive electrode active material layer;
A negative electrode in which a solid electrolyte layer having a chemically crosslinked portion is held on at least the surface of the negative electrode active material layer, and a solid electrolyte battery stacked such that both solid electrolyte layers face each other, A solid electrolyte battery, characterized in that a solid electrolyte layer for adhesion that bridges these solid electrolyte layers is interposed on the opposite surface of the solid electrolyte layer. 2. The solid electrolyte battery according to claim 1, wherein the solid electrolyte layer for adhesion mainly has a chemically crosslinked portion. 3. The solid electrolyte layer held by the positive electrode, the solid electrolyte layer held by the negative electrode, and at least one of the solid electrolyte layers for adhesion are supported by a separator. Item 6. The solid electrolyte battery according to Item 1. 4. The solid electrolyte battery according to claim 1, wherein the solid electrolyte layer for adhesion includes at least one of a vinylidene fluoride skeleton and an acrylonitrile skeleton in at least a part of a polymer matrix thereof. 5. A solid electrolyte layer held by the positive electrode, a solid electrolyte layer held by the negative electrode, and a solid electrolyte layer for adhesion include an acrylic skeleton in at least a part of a polymer matrix thereof. The solid electrolyte battery according to claim 1, wherein: 6. The solid electrolyte battery according to claim 5, wherein an ethylene oxide group is bonded to the acrylic skeleton. 7. A solid electrolyte layer having a chemically crosslinked portion,
A first step of forming at least a surface of each of a positive electrode active material layer of a positive electrode and a negative electrode active material layer of a negative electrode; and a raw material solution containing at least one of a polymer material and a polymerizable compound, the solid electrolyte layer on the positive electrode side or the negative electrode side. A second step of holding the positive electrode and the negative electrode so that the solid electrolyte layers on the positive electrode side and the negative electrode side face each other; and a step of gelling the raw material liquid. And a fourth step of forming a solid electrolyte layer for adhesion. 8. In the second step, the raw material liquid containing the polymer material in a dissolved state is applied to the surface of the solid electrolyte layer, and in the fourth step, the raw material liquid is allowed to cool by natural cooling to form a gel. The method for producing a solid electrolyte battery according to claim 7, wherein 9. The method according to claim 9, wherein in the second step, the raw material liquid is applied to a surface of the solid electrolyte layer, and in the fourth step, at least one of heating and energy ray irradiation is performed to promote gelation. The method for manufacturing a solid electrolyte battery according to claim 7. 10. The method according to claim 7, wherein in the second step, a separator impregnated with the raw material liquid is placed on a surface of the solid electrolyte layer. 11. In the first step, a raw material liquid containing at least one of a polymer material and a polymerizable compound is applied to each surface of the positive electrode active material layer and the negative electrode active material layer, and allowed to cool naturally. The method for producing a solid electrolyte battery according to claim 7, wherein the solid electrolyte layer is formed by gelling the raw material liquid by performing at least one of heating and energy beam irradiation. 12. The method according to claim 11, wherein, in the first step, a separator impregnated with the raw material liquid is placed on at least one surface of the positive electrode active material layer or the negative electrode active material layer. Of manufacturing a solid electrolyte battery.