JP2017183115A - Lithium ion battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium ion battery incorporating a crystalline oxide-based inorganic solid electrolyte having enhanced ion conductivity.SOLUTION: The lithium ion battery includes a positive electrode, a negative electrode, and a solid electrolyte layer. The solid electrolyte layer has a structure in which crystalline oxide-based inorganic solid electrolyte particles are arranged in a single layer. At least a part of the surface of the inorganic solid electrolyte particle is coated with an amorphous compound having lithium ion conductivity.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a lithium ion battery.

  Lithium ion secondary batteries are characterized by their light weight, high energy, and long life, and are widely used as power sources for portable electronic devices such as notebook computers, mobile phones, digital cameras, and video cameras. Yes. In addition, with the transition to a low environmental impact society, power sources for hybrid electric vehicles (HEVs) and plug-in HEVs (Plug-in Hybrid Electric Vehicles: PHEVs), as well as power storage for residential power storage systems, etc. It is also attracting attention in the field.

Conventionally, an organic electrolytic solution in which a lithium salt is dissolved in an organic solvent has been used as an electrolyte of a lithium ion secondary battery, and there has been a concern about safety associated with leakage.
By using a solid electrolyte instead of an electrolyte, all-solid-state batteries in which the positive electrode material, electrolyte, and negative electrode material are all solid have been proposed as a technology that dramatically improves safety by eliminating the need for flammable electrolytes. ing.
As a solid electrolyte used for an all solid state battery, for example, there is a disclosure of a technique using a sulfide-based material because of high lithium ion conductivity. However, sulfide-based materials have poor chemical stability, and when hydrogen sulfide is generated by exposure to the atmosphere or when a sulfide-based solid electrolyte and a positive electrode material are brought into direct contact with each other, there is no lithium on the interface. There are problems such as the appearance of a “deficient layer” of several nanometers, and a significant reduction in output characteristics. Furthermore, since the sulfide-based solid electrolyte has flexibility, the interfacial resistance between particles is reduced by pressurization to obtain high lithium ion conductivity, but a short circuit is likely to occur during pressurization. Therefore, it is necessary to ensure a certain thickness or more, and there is a problem from the viewpoint of increasing the electric capacity of the battery by thinning the solid electrolyte layer and increasing the active material filling amount.

  In order to solve the above problems, attempts have been made to use a metal oxide-based material such as a garnet-type oxide and a LISICON-type oxide having lithium ion conductivity and chemically stable as a solid electrolyte. However, since oxide-based materials have poor flexibility and are difficult to process, it is difficult to increase the ion conductivity by reducing the resistance of grain boundaries by pressurizing operation like sulfide-based solid electrolytes. Furthermore, since the oxide-based material is a brittle material, it is inferior in workability, and it is difficult to make the solid electrolyte layer thin. Therefore, it is difficult to increase the filling amount of the active material as an all solid battery and increase the electric capacity as a battery. Met.

  In order to solve the problems of the inorganic solid electrolyte as described above, attempts have been made to bind inorganic solid electrolyte particles using an insulating polymer to obtain high ion conductivity and excellent workability. For example, Patent Document 1 discloses a technique of a solid electrolyte in which inorganic solid electrolyte particles are bound with one or more plastic materials selected from the group consisting of polyethylene, polypropylene, styrene butadiene rubber, neoprene rubber, and silicon rubber. . In addition, since it is difficult to manufacture a layer having a thickness of one particle as shown in Patent Document 1 without causing a short circuit between the electrodes, in Patent Document 2, the hopping sites are made dense. There is a disclosure of a technique in which the use of a polymer has a small number of short circuits between electrodes without blocking the ion conduction path even when a plurality of particles are filled in the thickness direction of the layer.

JP-A-63-78405 Japanese Patent Laid-Open No. 2001-29779

As described above, there has never been a technique for operating an all-solid-state lithium ion battery by obtaining a crystalline oxide-based inorganic solid electrolyte layer having high chemical stability as a thin layer while maintaining processability. Therefore, a technique for obtaining an all-solid-state lithium ion battery using a highly safe oxide-based inorganic solid electrolyte has been desired.
The present invention has been proposed in view of such conventional circumstances, and a problem to be solved by the present invention is to provide a lithium ion battery incorporating an oxide-based solid electrolyte with improved ion conductivity. It is.

The present inventors diligently researched and repeated experiments to solve the above problems. As a result, the use of a solid electrolyte layer having a structure in which crystalline oxide-based inorganic solid electrolyte particles are arranged in a single layer and coated with an amorphous compound having lithium ion conductivity at the particle interface is safe. Thus, the present inventors have found that an all-solid lithium ion battery having a high electric capacity and a thin solid electrolyte layer can be obtained, thereby having a high electric capacity as a battery.
That is, the present invention is as follows.
[1]
A positive electrode, a negative electrode, and a solid electrolyte layer;
The solid electrolyte layer has a structure in which crystalline oxide inorganic solid electrolyte particles are arranged in a single layer, and at least a part of the surface of the inorganic solid electrolyte particles has an amorphous compound having lithium ion conductivity Lithium ion battery characterized by being coated with.
[2]
The lithium ion battery according to [1], wherein the solid electrolyte layer has a sheet shape.
[3]
An amorphous compound having lithium ion conductivity is present both between the positive electrode active material and the crystalline oxide-based inorganic solid electrolyte particle, and between the negative electrode active material and the crystalline oxide-based inorganic solid electrolyte particle, [ The lithium ion battery according to [1] or [2].
[4]
The crystalline oxide inorganic solid electrolyte particles have a structure arranged in a single layer, and at least a part of the surface of the inorganic solid electrolyte particles is coated with an amorphous compound having lithium ion conductivity. A solid electrolyte for a lithium ion battery.

  By using the solid electrolyte layer having the form according to the present invention, an all-solid lithium ion battery having safety and high battery capacity can be provided.

It is sectional drawing which shows roughly an example of the lithium ion secondary battery in this embodiment.

  Hereinafter, a mode for carrying out the present invention (hereinafter simply referred to as “the present embodiment”) will be described in detail. The present invention is not limited to the following embodiments, and various modifications can be made within the scope of the invention. In addition, the range described using "-" in this specification includes the numerical value described before and behind that.

FIG. 1 is a schematic cross-sectional view showing an example of a lithium ion battery in the present embodiment.
The lithium ion battery (lithium ion secondary battery) 100 includes a solid electrolyte layer 110, a positive electrode 140 and a negative electrode 150 that sandwich the solid electrolyte layer 110 from both sides, and a positive electrode current collector 160 (positive electrode) that sandwiches the laminate. ), A negative electrode current collector 170 (arranged outside the negative electrode), and a battery exterior 180 that accommodates them.
In the lithium ion battery 100 of the present invention, the solid electrolyte layer 110 has a structure in which the crystalline oxide inorganic solid electrolyte particles 120 are arranged in a single layer, and at least a part of the surface of the particles 120 is made of lithium ions. It is characterized by being coated with an amorphous compound 130 having conductivity.
In the present invention, the solid electrolyte layer has a structure in which crystalline oxide inorganic solid electrolyte particles are arranged in a single layer, and the surface of the particles is coated with an amorphous compound having lithium ion conductivity. Thus, the solid electrolyte layer can be thinned with high safety, and thereby, an all solid lithium ion battery having a high electric capacity as a battery can be realized.

[Positive electrode]
The positive electrode contains a positive electrode active material, and can contain a conductive assistant, a binder, an inorganic solid electrolyte for increasing ion conductivity, a polymer gel electrolyte, a polymer electrolyte, an additive, and the like as necessary.
As the positive electrode active material, a positive electrode active material used in a general lithium ion battery can be used. Specifically, Li—Co composite oxides such as LiCoO ₂ that are layered rock salt type positive electrode materials, Li—Ni composite oxides such as LiNiO ₂ , nickel-based compounds derived from these, LiNi (Co, Al) O ₂ , Ternary compound LiNi _1/3 Mn _1/3 Co _1/3 O ₂ , LiNi _0.5 Mn _0.5 O ₂ which is a nickel manganese compound, lithium-excess compound Li ₂ MnO ₃ —LiMO ₂ (M = Co, Ni, Mn), LiMn ₂ O ₄ , which is a spinel type cathode material, LiMn _1.5 Ni _0.5 O ₄ , LiFeO ₂ which is an olivine-based cathode material, LiMnPO ₄ , Li ₂ MSiO ₄ (M is a transition metal) ), LiMPO ₄ F (M is a transition metal), a high-capacity positive electrode material such as a vanadium oxide-based or sulfur-based positive electrode material can be used.

A positive electrode will not be specifically limited if it acts as a positive electrode of a lithium ion secondary battery, For example, it is obtained as follows.
First, a positive electrode mixture-containing paste is prepared by dispersing a positive electrode mixture obtained by mixing the positive electrode active material together with other components (for example, a conductive additive, a binder, etc.) used as necessary in a solvent. Next, this positive electrode mixture-containing paste is applied to a positive electrode current collector, dried to form a positive electrode mixture layer, and further pressurized to adjust the thickness as necessary to produce a positive electrode.
Examples of the conductive aid used as necessary in the production of the positive electrode include graphite; carbon black typified by acetylene black and ketjen black; carbon fiber and the like. The number average particle diameter (primary particle diameter) of the conductive assistant is preferably 10 nm to 10 μm, more preferably 20 nm to 1 μm.
Examples of the binder include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid, styrene butadiene rubber, and fluorine rubber.

The solid content concentration in the positive electrode mixture-containing paste is preferably 30 to 80% by mass, more preferably 40 to 70% by mass.
The positive electrode current collector is made of a metal foil such as an aluminum foil or a stainless steel foil. These materials may be carbon coated or those materials processed into a mesh shape.
If necessary, a method of filling the space between the particles with a substance having lithium ion conductivity can be used in order to maintain lithium ion conductivity with the solid electrolyte. As the substance having lithium ion conductivity, for example, an amorphous substance having lithium ion conductivity can be used. As the substance having amorphous lithium ion conductivity, a polymer electrolyte, an amorphous substance can be used. An inorganic compound having lithium ion conductivity can be used.

[Negative electrode]
As a negative electrode, if it acts as a negative electrode of a lithium ion secondary battery, it will not specifically limit, A well-known thing can be used.
The negative electrode preferably contains at least one material selected from the group consisting of a material capable of inserting and extracting lithium ions as a negative electrode active material and metallic lithium. Such materials include metal lithium, metal materials such as a material containing an element capable of forming an alloy with lithium, and the like;
For example, amorphous carbon (hard carbon), artificial graphite, natural graphite, graphite, pyrolytic carbon, coke, glassy carbon, organic polymer compound fired body, mesocarbon microbead, carbon fiber, activated carbon, graphite, carbon colloid, Examples thereof include carbon materials typified by carbon black. Among these, examples of the coke include pitch coke, needle coke, and petroleum coke. The fired body of an organic polymer compound is obtained by firing and polymerizing a polymer material such as phenol resin or furan resin at an appropriate temperature. In addition to carbon, the carbon material may contain a heterogeneous compound containing O, B, P, N, S, SiC, B ₄ C, or the like. As content of a different compound, it is preferable that it is 0-10 mass% with respect to the whole negative electrode active material. The metal material capable of forming an alloy with lithium may be a single metal or a semimetal, an alloy, or a compound, and one or more of these phases may be combined. It may be at least partly.
The number average particle diameter (primary particle diameter) of the negative electrode active material is preferably 0.1 μm to 100 μm, more preferably 1 μm to 10 μm.

A negative electrode is obtained as follows, for example.
First, a negative electrode mixture-containing paste is prepared by dispersing a negative electrode mixture prepared by mixing the negative electrode active material together with other components (for example, a conductive additive, a binder, etc.) used as necessary in a solvent. Next, this negative electrode mixture-containing paste is applied to a negative electrode current collector, dried to form a negative electrode mixture layer, and further pressurized to adjust the thickness as necessary to produce a negative electrode.
Here, the solid content concentration in the negative electrode mixture-containing paste is preferably 30 to 80% by mass, and more preferably 40 to 70% by mass. The negative electrode current collector is made of a metal foil such as a copper foil, a nickel foil, or a stainless steel foil.
Examples of the conductive aid used as necessary in the production of the negative electrode include graphite; carbon black typified by acetylene black and ketjen black; carbon fiber and the like. The number average particle diameter (primary particle diameter) of the conductive assistant is preferably 0.1 μm to 100 μm, more preferably 1 μm to 10 μm. Examples of the binder include PVDF, PTFE, polyacrylic acid, styrene butadiene rubber, and fluorine rubber.
If necessary, in order to maintain lithium ion conductivity with the solid electrolyte, a method of filling between the particles with a substance having lithium ion conductivity can be used. As the substance having lithium ion conductivity, for example, an amorphous substance having lithium ion conductivity can be used. As the substance having amorphous lithium ion conductivity, a polymer electrolyte, an amorphous substance can be used. An inorganic compound having lithium ion conductivity can be used.

[Solid electrolyte layer]
The solid electrolyte layer of the present invention has a structure in which crystalline oxide inorganic solid electrolyte particles are arranged in a single layer, and at least a part of the particle surface is coated with an amorphous compound having lithium ion conductivity. Shall.
In the following description, “crystalline oxide inorganic solid electrolyte particles” may be referred to as “solid electrolyte particles” or simply “particles”.
As the solid electrolyte particles, any crystalline oxide inorganic solid electrolyte having lithium ion conductivity can be used. For example, γ-LiPO ₄ type oxide, reverse fluorite type oxide, NASICON type oxide, perovskite type oxide and garnet type oxide are used, and the NASICON type oxide Li _1.3 Ti _1.7 (PO ₄ ) ₃ , La _{2 / 3-x} Li _3x TiO ₃ which is a perovskite oxide, and Li ₇ La ₃ Zr ₂ O ₁₂ which is a garnet oxide are preferably used. For the purpose of increasing ion conductivity, improving chemical stability, and improving workability, crystalline oxide solid electrolyte particles in which the above basic crystal structure is substituted or element is substituted by doping may be used. it can. Preferably, NASICON type oxide Li _1.3 Ti _1.7 (PO ₄ ) ₃ and garnet type oxide Li ₃ La ₇ Zr ₂ O ₁₂ are used, and most preferably element substitution product Li ₆ of garnet type oxide _{. 25 Al 0.25 La 3 Zr 2 O} 12, Li 7 La 3 Zr 2-x Nb x O 12 (0 <X <0.95), Li 7 La 3 Zr 2-x Ta x O 12 (0 <X <0.95) is used.

As the shape of the crystalline oxide-based inorganic solid electrolyte particles, either spherical or irregular shapes can be used. The crystalline oxide inorganic solid electrolyte particles preferably have a high density in order to ensure high ion conductivity, and those having a relative density of 80 to 100% of each crystalline oxide inorganic solid electrolyte are used. Those having a relative density of 90 to 100% are preferably used, and those having a relative density of 95 to 100% are most preferably used. Here, the relative density is a theoretical density obtained from a lattice constant value obtained from an XRD measurement method or the like using the “true density” of the sample obtained by a general measurement method such as a liquid substitution method or a gas substitution method as an actual measurement density. From
Relative density (%) = (sample actual density / theoretical density) × 100
Is required. By setting the relative density to 80% or more, the resistance derived from the grain boundaries in the crystal grains and the resistance derived from the voids are reduced, and the lithium ion conductivity of the grains themselves is improved. By setting it to 100% or less, it is possible to reduce the burden of complicated operations such as heating at a high temperature for reducing grain boundaries and voids of particles and compression at a high pressure.

The structure in which particles are arranged in a single layer means a structure in which one single particle is arranged in the thickness direction of the layer and a large number of particles are arranged in the direction of the layer. Even when the number of particles in the thickness direction of the layer is not one, such as when relatively flat particles overlap, the maximum number of particles in the in-layer direction may be 15% or less, and 5% or less Preferably it is present.
The solid electrolyte layer may have a structure in which particles are arranged in a single layer, and the particles may be used even if they are fixed or exist in an independent state. The space between particles when present in an independent state can be used without any space, but if necessary, an amorphous insulator such as an insulating resin can be used to prevent battery short-circuiting due to dendrite formation. Etc., and can be used. As a state where the particles are fixed to each other, it can be used as a sheet. The sheet shape means, for example, an extremely thin planar shape as compared with the length and width. In general, a sheet having a thickness of 0.2 mm or more is referred to as a sheet, and a film having a thickness of less than 0.2 mm is referred to as a film. For fixing the particles, an amorphous resin, an inorganic compound, or the like can be used.
Further, by using the electrolyte layer of the present invention, if the cell thickness is the same and the electrolyte layer is made thinner, more electrode active material can be packed, and the electric capacity as a battery can be increased.

  As a method for arranging the particles in a single layer, for example, a structure in which the particles are arranged in a single layer can be obtained by placing the particles on the adhesive layer and removing the particles not fixed to the adhesive layer. As the adhesive layer, an adhesive tape or a substrate coated with easily removable grease or the like is also used. As a method for removing particles that are not fixed to the adhesive layer, the entire adhesive layer on which particles are placed is reversed, the particles that are not fixed are dropped and removed. For example, a method of removing particles by blowing them off can be used. As a method for fixing the particle layer arranged in a single layer, for example, a method of fixing by hot melt using a resin, or a method of casting in which a resin dissolved in a solvent is applied to the particle layer can be used. The ion-conductive amorphous compound may be coated on the crystalline oxide-based inorganic solid electrolyte particles in advance, and the particles may be arranged in a single layer, and then fixed by heat treatment or the like. If short circuit does not occur, the crystalline oxide inorganic solid electrolyte particles do not necessarily have to be bound to each other, and can be used, for example, in a form in which a single particle layer is formed on the positive electrode or the negative electrode.

By fixing the particle layer arranged in one layer using a resin, the solid electrolyte layer becomes a flexible sheet, and can follow the deformation of the battery.
In addition, when fixing the particle layer arranged in one layer using resin, in order to ensure the lithium ion conductivity of a solid electrolyte layer, it is necessary to expose the particle | grains on both sides of a sheet | seat. When the particles are coated with a resin, the particles can be exposed using an etching method or the like.

As the size of the crystalline oxide inorganic solid electrolyte particles, particles having an average particle size of 5 to 100 μm are used, preferably an average particle size of 10 to 80 μm is used, and particles of 20 to 50 μm are most preferably used. By setting the particle diameter to 5 μm or more, the physical strength of the solid electrolyte layer is increased, and a short circuit during processing can be prevented. By setting the particle diameter to 100 μm or less, sufficient lithium ion conductivity between the positive electrode and the negative electrode can be obtained.
The in-plane coverage by the solid electrolyte single particles of the solid electrolyte layer is represented by the ratio of the area occupied by the particles in the unit single particle layer area. The coverage is used in the range of 50 to 98%, preferably in the range of 60 to 90%. By setting the coverage to 50% or more, the lithium ion conductivity per unit single particle layer area can be sufficiently increased, and by setting the coverage to 98% or less, the film is given flexibility and the film is damaged due to embrittlement. Can be prevented.

[Coating with an amorphous compound having lithium ion conductivity]
In the present invention, at least a part of the surface of the particles of the solid electrolyte layer can be used in a state where the amorphous compound having lithium ion conductivity is coated. The particle surface is preferably a particle interface. The “particle interface” refers to a surface where the particles of crystalline oxide inorganic solid electrolyte particles are in contact with each other, and a surface where the crystalline oxide inorganic solid electrolyte particles are in contact with the negative electrode and the positive electrode. The coverage of the amorphous compound having lithium ion conductivity on the surface of the crystalline oxide-based inorganic solid particles is 5 to 100%, preferably 10 to 80%. By setting it to 5% or more, sufficient lithium ion conductivity between the crystalline oxide inorganic solid electrolyte particles and the positive electrode and the negative electrode can be obtained. By setting it to 100% or less, the crystalline oxide inorganic The binding property of the solid electrolyte particles is increased, and a short circuit can be prevented. When coating an amorphous compound having lithium ion conductivity, in order to maintain a stable structure in which crystalline oxide-based inorganic solid electrolyte particles are arranged in a single layer, an insulating amorphous compound is simultaneously added to the crystalline oxide. The inorganic solid electrolyte particles may be coated.
The amorphous compound having lithium ion conductivity may be present at the interface between the crystalline oxide inorganic solid electrolyte particles and the negative electrode active material, and the interface between the crystalline oxide inorganic solid electrolyte particles and the negative electrode active material, More preferably, it is present both at the interface between the crystalline oxide-based inorganic solid electrolyte particles and the positive electrode active material.

  The crystalline oxide-based inorganic solid electrolyte particles may be arranged in one layer after being coated with an amorphous compound having ion conductivity in advance, or may be coated after being arranged in one layer. If the amorphous compound is a polymer electrolyte, the coating is applied to the crystalline oxide inorganic solid electrolyte particles using a polymer solution dissolved in a solvent, and then the solvent is removed by heating, decompression, etc. And a method of softening the polymer by heating and coating the particles by pressure bonding or the like can be used. If the amorphous compound is a gel polymer, apply a solution containing carbonate-based electrolyte, monomer, and polymerization initiator to the crystalline oxide-based inorganic solid electrolyte particles, start polymerization by heat, etc., and cover the gel polymer can do. If the amorphous compound is an inorganic compound, a method of coating by pressure or pressure bonding, or a method of coating by sputtering or the like can be used.

As the amorphous compound having lithium ion conductivity, any organic or inorganic substance can be used as long as it is an amorphous compound having lithium ion conductivity. As the amorphous compound having organic lithium ion conductivity, a polymer electrolyte or a gel polymer electrolyte is used. As the polymer electrolyte, for example, LiBr, LiCl, LiI, LiSCN, LiBF ₄ , LiAsF ₆ , LiClO ₄ , CH ₃ COOLi, CF ₃ COOLi, LiCF ₃ SO ₃ , LiPF ₆ , LiN (CF ₃ SO ₂ ) ₂ as a lithium salt. Polymers such as polyethylene oxide, polypropylene oxide, polyvinylidene fluoride, and polyacrylonitrile containing LiC (CF ₃ SO ₂ ) ₃ can be used. Examples of the gel polymer electrolyte include polymers such as polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), and polyethylene oxide (PEO), for example, ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl A combination of carbonates such as carbonate (DEC) and ethyl methyl carbonate (EMC) can be used. Preferably, polyethylene oxide using LiClO ₄ or LiN (CF ₃ SO ₂ ) ₂ as a lithium salt is used as a polymer electrolyte. As the amorphous inorganic compound, oxide-based glass, sulfide glass, amorphous thin film, or the like is used. As the oxide glass, 42.5Li ₂ O · 57.5B ₂ O ₃ , 40Li ₂ O · 60SiO ₂ , 60Li _{2 is used. O · 40SiO 2, 50Li 2 O} · 50Nb 2 O 5, 39Li 2 O · 13B 2 O 3 · 48SiO 2, 60LiPO 3 · 40LiF, 70LiPO 3 · 30LiCl, 67LiPO 3 · 33LiBr, 67LiPO 3 · 33LiI, 67LiPO 3 · 33Li ₂ SO _4, sulfide as a glass _{50Li 2 S · 50GeS 2, 50Li} 2 S · 50SiS 2, 60Li 2 S · 30SiS 2 · 10Al 2 S 3, 37Li 2 S · 18P 2 S 5 · 45LiI, 30Li 2 S · 26B ₂ S ₃ · 44LiI, 30Li _{S · 21SiS 2 · 9B 2 S} 3 · 40LiI, 57Li 2 S · 38SiS 2 · 5Li 4 SiO 4, Li 3.6 Si 0.6 P 0.4 O 4 as an amorphous thin _film, Li _{3.4 V 0.6} Si _0.4 O ₄ , Li _3.3 PO _3.9 N _0.37 (LIPON) can be used. Particularly preferably, the polymer electrolyte is a gel polymer using DMC as a solvent, LiPF ₆ as a lithium salt, and gelled using a polyfunctional acrylate polymerization initiator, and the polymer electrolyte is LiClO ₄ , LiN ( Polyethylene oxide using CF ₃ SO ₂ ) ₂ and LIPON can be used as the amorphous inorganic compound.

<Production method of battery>
The lithium ion secondary battery in the present embodiment is produced by a known method using the above-described positive electrode, negative electrode, and solid electrolyte particles. For example, a multilayer structure in which a positive electrode, a negative electrode, and a solid electrolyte particle layer are interposed, and a multilayer structure in which an electron conductor is interposed between a plurality of positive electrodes and negative electrodes that are alternately stacked. The electrode laminated body is configured according to the configuration or the like. Next, the electrode laminate is accommodated in a battery case (exterior) and sealed, whereby the lithium ion battery of this embodiment can be produced.
It is preferable to apply a pressure of 0.1 to 4000 kgf / cm ² to the opposing surfaces of the positive electrode and the negative electrode at the time of producing the battery, more preferably pressurizing with a pressure of 0.1 to 100 kgf / cm ² , Most preferably, pressurization is performed at a pressure of 0.5 to 15 kgf / cm ² . When the pressure is 0.1 kgf / cm ² or more, the contact state between the electrode active material and the solid electrolyte particles is improved, and the battery characteristics are improved. By setting the pressure to 4000 kgf / cm ² or less, a short circuit due to internal damage of the battery can be prevented. The battery can be operated while maintaining the pressurized state at the time of battery production, but can also be operated without pressure if there is no problem with the charge / discharge characteristics.
The shape of the lithium ion secondary battery of the present embodiment is not particularly limited, and, for example, a cylindrical shape, an elliptical shape, a rectangular tube shape, a button shape, a coin shape, a flat shape, a laminate shape, and the like are suitably employed.
Further, the solid electrolyte of the present embodiment is applicable not only to the lithium ion secondary battery as described above but also to other batteries.
As mentioned above, although the form for implementing this invention was demonstrated, this invention is not limited to the said embodiment. The present invention can be variously modified without departing from the gist thereof.

Examples and comparative examples performed for confirming the effects of the present invention will be described below.
[Example 1]
<Deposition of single particle film>
As crystalline oxide-based inorganic particles, Li _1.3 Ti _1.7 (PO ₄ ) ₃ (LATP), which is a NASICON type oxide manufactured by Toshima Seisakusho, is used as an amorphous compound having lithium ion conductivity. A film was formed using a compound in which ethylene oxide (PEO) and LiClO ₄ were combined.
On a stainless steel smooth substrate, a water-soluble adhesive tape (3M Water Soluble Adhesive water-soluble tape) was attached in an area of 3 cm × 3 cm so that the adhesive surface was on top. LATP particles classified by sieving with an opening of 38 to 45 μm in advance were placed on the adhesive surface of the adhesive tape, and the entire stainless steel substrate was inverted to remove excess particles that were not fixed to the adhesive tape. Furthermore, the operation of removing excess particles by placing LATP particles on an adhesive tape and inverting it was repeated several times, and single particles were arranged.

  A polycycloolefin (COP) manufactured by Nippon Zeon was dissolved in decalin to prepare an 8 wt% COP solution. Next, the COP solution was dropped onto the surface on which the single particles were arranged so as to cover the surface, and spin coating was performed using a spin coater manufactured by MIKASA under the conditions of 300 rpm and 60 sec. After the coating, the stainless steel substrate was heated at 90 ° C. for 20 minutes using an AS ONE hot stirrer. The same spin coating and heating operations were repeated 4 times to obtain a film in which the single particle film and the adhesive tape were integrated. Next, the membrane in which the single particle membrane and the adhesive tape were integrated was placed in a beaker containing 100 ml of ethanol and sufficiently immersed. Next, when the beaker was heated to 65 ° C. on a water bath to dissolve the adhesive tape, the single particle film was separated. The obtained single particle film was dried overnight under reduced pressure at 80 ° C. to obtain a single particle film with one side exposed.

<Surface exposure operation of single particle film>
The obtained single particle film with one side exposed particle is placed in the chamber of Mori Engineering MPC-600 Co., Ltd. with the surface where the solid electrolyte particle surface is not exposed as the upper side, substrate temperature of 40 ° C., oxygen gas Plasma treatment was performed for 10 minutes at a flow rate of 100 CCM and an RF output of 100 W. The membrane after the treatment was taken out of the chamber to obtain a membrane in which single particles were arranged with both surfaces of the solid electrolyte particles exposed on the surface.

<Measurement of coverage of single particle film>
SEM observation of the obtained film SEM observation apparatus: VE-9800 manufactured by KEYENCE Corporation
Acceleration voltage: 1.2KV
Spot diameter: 6 (set value of the device)
Degree of vacuum: 3Pa
Detector: Secondary electron detector A sample was fixed to a sample stage using a conductive double-sided tape, and the surface not etched at a magnification of 200 times was observed under non-deposition conditions. The area occupied by the particles was calculated by software attached to the apparatus, and by dividing by the total area, the ratio of the particles of the single particle film was calculated to obtain the particle coverage. The same calculation was repeated three times while changing the field of view, and the average was calculated. As a result, the coverage was 79.1%.

<Coating of lithium ion conductive amorphous compound>
Compound obtained by combining polyethylene oxide (PEO) and LiClO ₄ in order to coat a crystalline oxide single particle film with exposed particles on both sides with a lithium ion conductive amorphous compound Coated with.
Aldrich Poly (ethylene oxide), average Mv ˜4,000,000 and Kanto Chemical LiClO ₄ were mixed at a unit molar ratio of 15: 1 (oxygen mole of PEO: Li mole of LiClO ₄ ). And a 10 wt% polymer solution was prepared. Next, in a dry room where the dew point was kept at -70 ° C, an operation of dropping a small amount of polymer liquid onto the surface of the etched single particle film, gradually reducing the pressure and drying at room temperature was performed with a Mitutoyo 457-401 thickness gauge. The measurement was repeated until a single particle film having a thickness of 5 μm and coated with PEO was obtained. As a result of observation using the SEM apparatus, it was confirmed that the PEO-coated surface of the single particle film was covered with PEO, and no particles were exposed.

<Battery evaluation>
(1) Positive electrode formation A positive electrode was formed on a single particle film 14 mm x 20 mm coated with PEO. Vanadium alkoxide (triisopropoxy vanadium oxide) was dissolved in dehydrated ethanol to prepare a 13 wt% solution. Subsequently, the single particle film coated with PEO was placed on a glass substrate with the surface not coated with PEO as the upper surface, and the prepared vanadium alkoxide solution was dropped, followed by hydrolysis by dropping water. Then, after drying at room temperature, drying was performed at 80 ° C. for 10 hours. The weight of the active material was 0.50 mg / cm ² .
(2) Preparation of battery for evaluation The battery uses lithium metal as the negative electrode, and a single particle film is placed thereon so that the lithium metal and the PEO-coated surface are in contact with each other, and the vanadium positive electrode is on the upper surface. Then, a tab for connecting the power source was attached to the positive electrode plate and the negative electrode plate so that charging and discharging were possible. The positive electrode and negative electrode sides were sandwiched between flat plates and pressurized with a pressure corresponding to 1 kg / cm ² .
(3) Evaluation of charge / discharge capacity For all solid state batteries, the discharge capacity at a specific discharge current was measured according to the following procedure, and the electric capacity was evaluated.
The measurement was performed using a charge / discharge device ACD-01 (trade name) manufactured by Asuka Electronics Co., Ltd. and a thermostatic chamber IN-804 (trade name) manufactured by Yamato Scientific Co., Ltd.
The lithium ion secondary battery was subjected to constant current discharge at a current value of 0.0028 mA (0.01 C Rate), and the electric capacity until reaching 2.0 V was determined as the initial discharge capacity. After the discharge, constant current charging was performed up to 4.0 V at a current value of 0.028 mA (0.01 C Rate). Subsequently, a constant current discharge is performed at a current value of 0.0028 mA (0.01 C Rate) to obtain an electric capacity until reaching 2.0 V, and charging is performed until it reaches 4.0 V at 0.0028 mA (0.01 C Rate). The charge and discharge were repeated a total of 6 times.
The initial discharge capacity, the sixth discharge capacity, and the capacity retention rate are shown.
Capacity retention rate = [6th discharge capacity] / [1st discharge capacity] × 100
The initial charge capacity was 60 mAh / g, the sixth discharge capacity was 58 mAh / g, and the capacity retention rate was 96.7%.

[Example 2]
LiTFSI (lithium bis (trifluoromethanesulfonyl) imide) was used as the salt combined with PEO for coating the amorphous compound having lithium ion conductivity of Example 1, and the unit molar ratio was 17: 1 (oxygen mole of PEO: LiTFSI). The same operation was performed except that a compound under the condition of Li mol) was prepared, and a battery was produced and evaluated. As a result, the initial charge capacity was 65 mAh / g, and the sixth discharge capacity was 62 mAh / g. The capacity retention rate was 95.4%.
[Example 3]
<Coating with LiPON>
The surface of the single particle film in which part of the surface of the solid electrolyte particles produced by the same method as described in Example 1 was exposed on both sides of the film was coated with amorphous LIPON using an RF sputtering apparatus. The LIPON film was formed under the following conditions with the surface of the single particle film etched upward. The film thickness was 500 nm, and the XRD of the surface on which LIPON was formed was measured. As a result, a halo pattern was observed in the vicinity of 2θ = 22 ° to 26 °, and LIPON was confirmed to be amorphous.
RF sputtering condition gas: N ₂
Pressure: 1.0Pa
Target: Li ₃ PO ₄
Target-base distance: 6cm
Rf output: 30w
Deposition time: 300 min
<Battery evaluation>
(1) Positive electrode formation A positive electrode was formed on a single particle film 14 mm × 20 mm coated with LiPON. The method was the same as the positive electrode forming method described in Example 1, and the positive electrode was formed on the surface not coated with LIPON. The active material weight was 0.51 mg / cm ² .
(2) Preparation of battery for evaluation The negative electrode uses a 14 mm x 20 mm lithium plate. The single particle film is placed on the lithium plate so that the LIPON film is in contact, and these are placed in an aluminum laminate sheath so that charging and discharging are possible. A tab for power supply connection was attached to the plate and the negative electrode plate and sealed. The positive electrode and negative electrode sides were sandwiched between flat plates and pressurized with a pressure corresponding to 1 kg / cm ² .
(3) Evaluation of charge / discharge capacity The same evaluation as in Example 1 was performed, the initial discharge capacity was 51 mAh / g, the sixth discharge capacity was 47 mAh / g, and the capacity retention rate was 92.2%.

[Example 4]
Li _6.25 Al _0.25 La ₃ Zr ₂ O ₁₂ (LLZO) is used as a crystalline oxide-based inorganic solid electrolyte particle, and a lithium ion battery is formed using a gel polymer as an amorphous compound having lithium ion conductivity. Produced.
(1) Formation of LLZO Single Particle Film A single particle film was formed using LLZO as the crystalline oxide inorganic solid electrolyte particles. On a stainless steel smooth substrate, a water-soluble adhesive tape (3M Water Soluble Adhesive water-soluble tape) was attached in an area of 3 cm × 3 cm so that the adhesive surface was on top. The LLZO particles classified by sieving with 38 to 45 μm openings were placed on the pressure-sensitive adhesive surface of the pressure-sensitive adhesive tape and inverted together with the stainless steel substrate to remove excess particles not fixed to the pressure-sensitive adhesive tape. Furthermore, the operation of removing excess particles by placing the LLZO particles on an adhesive tape and inverting it was repeated several times to obtain a state where single particles were arranged.
A polycycloolefin (COP) manufactured by Nippon Zeon was dissolved in decalin to prepare an 8 wt% COP solution. Next, the COP solution was dropped onto the surface on which the single particles were arranged so as to cover the surface, and spin coating was performed using a spin coater manufactured by MIKASA under the conditions of 300 rpm and 60 sec. After the coating, the stainless steel substrate was heated at 90 ° C. for 20 minutes using an AS ONE hot stirrer. The same spin coating and heating operations were repeated 4 times to obtain a film in which the single particle film and the adhesive tape were integrated. Next, the membrane in which the single particle membrane and the adhesive tape were integrated was placed in a beaker containing 100 ml of ethanol and sufficiently immersed. Next, when the beaker was heated to 65 ° C. on a water bath to dissolve the adhesive tape, the single particle film was separated. The obtained single particle film was dried overnight under reduced pressure at 80 ° C. to obtain a single particle film with one surface exposed.
The surface exposure operation of the single particle film was the same as that described in Example 1 to obtain a single particle film in which the surfaces of the solid electrolyte particles were exposed on both surfaces of the film.
(2) Formation of gel polymer on negative electrode 92.8% by weight of electrolyte solution manufactured by Kishida Chemical Co., Ltd. containing 1 mol / L of LiPF ₆ and EC: EMC ratio of 3: 7 (vol / vol%) as a monomer A polymer solution containing 7% by weight of a functional acrylate (dipentaerythritol hexaacrylate) and 0.2% by weight of Perkadox 16 manufactured by Kayaku Akzo Corporation as a polymerization initiator was prepared. Next, a polyethylene microporous film having a thickness of 20 μm was placed on the lithium metal plate, and the above polymer solution was dropped from above to add an amount capable of holding the liquid by the polyethylene microporous membrane. Next, the polyethylene metal microporous film containing the lithium metal plate and the polymer solution was heated at 100 ° C. for 20 minutes to polymerize the polymer solution. After the heating operation, it was confirmed that the polymer liquid of the polyethylene microporous membrane containing the polymer liquid was polymerized and gelled.
(3) Positive electrode formation Positive electrode formation was performed on a 14 mm x 20 mm aluminum plate. Vanadium alkoxide (triisopropoxy vanadium oxide) was dissolved in dehydrated ethanol to prepare a 13 wt% solution. Subsequently, the vanadium alkoxide solution prepared on the aluminum substrate was dropped, and then water was added dropwise for hydrolysis. Then, after drying at room temperature, drying was performed at 80 ° C. for 10 hours. The weight of the active material was 0.50 mg / cm ² .
(4) Preparation of battery for evaluation The single particle film is placed on the negative electrode in which the gel electrolyte is formed on the lithium metal plate so as to be in contact with the gel electrolyte, and the positive electrode material and the single particle film are in contact with the positive electrode plate thereon. Overlapped so that. These were put in an aluminum laminate exterior and a power supply tab was attached to the positive electrode plate and the negative electrode plate so that charging and discharging were possible and sealed. The positive electrode and negative electrode sides were sandwiched between flat plates and pressurized with a pressure corresponding to 1 kg / cm ² .
(5) Evaluation of charge / discharge capacity Charge / discharge was evaluated in the same manner as in Example 1. The initial charge / discharge capacity was 54 mAh / g, the sixth discharge capacity was 49 mAh / g, and the capacity retention rate was 90.7%.
[Example 5]
After forming the single particle film described in Example 2, the surface not etched by the same method as described in Example 2 was coated with PEO containing LiTFSI at a thickness of 5 μm, and both surfaces of the single particle film were LiTFSI. A single particle film coated with PEO containing was formed. When the charge / discharge capacity was evaluated using the same method except that this film was used, the initial charge / discharge capacity was 85 mAh / g, the sixth discharge capacity was 78 mAh / g, and the capacity retention rate was 91.8. %Met.

[Comparative Example 1]
In the solid electrolyte layer, the only difference is that the crystalline oxide-based inorganic particles are not coated with an amorphous compound, and the charge / discharge evaluation was performed under the conditions of Example 1. Confirmed not to.

[Comparative Example 2]
<Double particle layer film>
Li _1.3 Ti _1.7 (PO ₄ ) ₃ (LATP), a NASICON type oxide manufactured by Toshima Seisakusho, was used as the crystalline oxide-based inorganic particles, and polyethylene oxide ( A film was formed using a compound in which PEO) and LiClO ₄ were combined.
A water-soluble adhesive tape (3M Water-Soluble Wave Solder Tape 5414) is pasted on a stainless steel smooth substrate with an area of 2 cm ² so that the adhesive surface is on top, and classified by sieving with an opening of 38 to 45 μm in advance. The prepared LATP particles were placed so that the particle layer had a thickness of about 100 μm, and the surface was smoothed.
A polycycloolefin (COP) manufactured by Nippon Zeon was dissolved in decalin to prepare an 8 wt% COP solution. Next, the COP solution was dropped in an amount covering the surface on which the particles were arranged, and spin coating was performed using a spin coater manufactured by MIKASA under the conditions of 300 rpm and 60 sec. After the coating, the stainless steel substrate was heated at 90 ° C. for 20 minutes using an AS ONE hot stirrer. The above spin coating and heating operation were repeated four times to obtain a film in which a plurality of particle films and an adhesive tape were integrated. Next, the membrane in which the plurality of particle membranes and the adhesive tape were integrated was placed in a beaker containing 100 ml of ethanol and sufficiently immersed. Next, when the beaker was heated to 65 ° C. on a water bath to dissolve the adhesive tape, a multi-particle film was separated. The obtained multiple particle film was dried overnight under reduced pressure at 80 ° C. to obtain a multiple particle film with one surface exposed.
<Surface exposure operation of double particle film>
Etching was performed using the same method as in Example 1 to form a film in which both surfaces of the particle layer were exposed.
<Positive electrode formation, production of battery for evaluation, evaluation of discharge capacity>
When the positive electrode was formed, the evaluation battery was produced, and the discharge capacity was evaluated using the same method as in the example, an initial discharge capacity of 20 mAh / g was obtained, and no discharge capacity was obtained in the sixth cycle.
Table 1 summarizes the evaluation results of the batteries of the examples and comparative examples.

  As is apparent from Table 1, Comparative Example 1 in which the crystalline oxide-based inorganic solid electrolyte particles were not coated with the amorphous compound did not operate as a battery, and in Comparative Example 2 in which the solid electrolyte layer was a double particle film. A sufficient discharge capacity could not be obtained. In contrast, in the batteries of Examples in which crystalline oxide inorganic solid electrolyte particles are arranged in a single layer and the surface of the particles is coated with an amorphous compound having lithium ion conductivity, all have a high initial discharge capacity. And a high capacity could be maintained even after 60 cycles of charge and discharge.

  The lithium ion battery of the present invention has a high battery capacity and can be widely applied as a power source for portable electronic devices such as notebook computers, mobile phones, digital cameras, video cameras, and the like.

DESCRIPTION OF SYMBOLS 100 Lithium ion secondary battery 110 Solid electrolyte layer 120 Crystalline oxide type inorganic solid electrolyte particle 130 Amorphous compound having lithium ion conductivity 140 Positive electrode 150 Negative electrode 160 Positive electrode current collector 170 Negative electrode current collector 180 Exterior

Claims (4)

A positive electrode, a negative electrode, and a solid electrolyte layer;
The solid electrolyte layer has a structure in which crystalline oxide inorganic solid electrolyte particles are arranged in a single layer, and at least a part of the surface of the inorganic solid electrolyte particles has an amorphous compound having lithium ion conductivity Lithium ion battery characterized by being coated with.   The lithium ion battery according to claim 1, wherein the solid electrolyte layer has a sheet shape.   An amorphous compound having lithium ion conductivity is present both between the positive electrode active material and the crystalline oxide-based inorganic solid electrolyte particle, and between the negative electrode active material and the crystalline oxide-based inorganic solid electrolyte particle. Item 3. The lithium ion battery according to Item 1 or 2.   The crystalline oxide inorganic solid electrolyte particles have a structure arranged in a single layer, and at least a part of the surface of the inorganic solid electrolyte particles is coated with an amorphous compound having lithium ion conductivity. A solid electrolyte for a lithium ion battery.

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