WO2020203545A1

WO2020203545A1 - Composite electrode active material, electrode composition, electrode sheet for all-solid-state secondary battery and all-solid-state secondary battery, and methods for manufacturing composite electrode active material, electrode sheet for all-solid-state secondary battery, and all-solid-state secondary battery

Info

Publication number: WO2020203545A1
Application number: PCT/JP2020/013311
Authority: WO
Inventors: 広磯島
Original assignee: 富士フイルム株式会社
Priority date: 2019-03-29
Filing date: 2020-03-25
Publication date: 2020-10-08
Also published as: JP7061728B2; JPWO2020203545A1

Abstract

Provided are a composite electrode active material including an active material and a covering layer covering the active material, an electrode composition, an electrode sheet for an all-solid-state secondary battery, and an all-solid-state secondary battery, and methods for manufacturing the composite electrode active material, the electrode sheet for an all-solid-state secondary battery and the all-solid-state secondary battery, wherein: the covering layer contains an inorganic solid electrolyte and a conduction promoting agent; and lithium atoms and carbon atoms contained in the covering layer satisfy a relationship defined by formula (I) in relation to the number of atoms.　Formula (I) A1<B1 In the formula, A1 represents the ratio C/Li of the number of carbon atoms to the number of lithium atoms in a region A having a thickness 0.5 μm toward the outside from an active material contacting portion of the covering layer, and B1 represents the ratio C/Li of the number of carbon atoms to the number of lithium atoms in a region B having a thickness 0.5 μm toward the inside from the surface of the covering layer. Here, B1 is at most equal to 99/1.

Description

Method for manufacturing composite electrode active material, electrode composition, electrode sheet for all-solid secondary battery and all-solid secondary battery, and composite electrode active material, electrode sheet for all-solid secondary battery and all-solid secondary battery

The present invention relates to a composite electrode active material, an electrode composition, an electrode sheet for an all-solid secondary battery and an all-solid secondary battery, and a composite electrode active material, an electrode sheet for an all-solid secondary battery and an all-solid secondary battery. Regarding the manufacturing method of.

In the all-solid-state secondary battery, the negative electrode, the electrolyte, and the positive electrode are all made of solid, and the safety and reliability, which are the problems of the battery using the organic electrolytic solution, can be greatly improved. It is also said that it will be possible to extend the service life. Further, the all-solid-state secondary battery can have a structure in which electrodes and electrolytes are directly arranged side by side and arranged in series. Therefore, it is possible to increase the energy density as compared with a secondary battery using an organic electrolytic solution, and it is expected to be applied to an electric vehicle, a large storage battery, or the like.

The electrode active material layer of such an all-solid-state secondary battery usually contains an inorganic solid electrolyte and an active material. The active material repeats expansion and contraction by charging and discharging the all-solid-state secondary battery. Therefore, voids are generated between the solid particles (active material, inorganic solid electrolyte, conductive additive, etc.), which causes an increase in battery resistance. As an all-solid-state secondary battery for dealing with this problem, for example, in Patent Document 1, at least one electrode of a positive electrode and a negative electrode is coated with a coating layer containing a conductive agent and a lithium ion conductive inorganic solid electrolyte. Lithium secondary batteries having active material particles are described.
Further,

Patent Documents

2 and 3 describe techniques for coating the surface of active material particles used in a lithium ion secondary battery with a solid electrolyte, a conductive material, a lithium ion conductive polymer, or the like.

JP-A-2003-509492 Japanese Unexamined Patent Publication No. 2016-66584 Japanese Unexamined Patent Publication No. 2002-373634

In recent years, research and development for improving the performance and practical application of electric vehicles have progressed rapidly, and the battery performance required for all-solid-state secondary batteries has also increased. Negative electrode active materials that can be alloyed with lithium have high ionic conductivity and are attracting attention because they contribute to improving (initial) battery performance, but on the other hand, expansion and contraction due to charge and discharge are large and the above problems are likely to occur. ..
Under such circumstances, when the present inventor proceeded with the study on the active material used for the all-solid secondary battery, a conductive agent, an inorganic solid electrolyte, and further lithium ion conduction as described in Patent Documents 1 to 3 were carried out. Even if active material particles coated with a sex polymer or the like are used, it is still sufficient in that it imparts excellent battery characteristics (for example, characteristics for maintaining discharge capacity when charging and discharging at a high rate are repeated) to an all-solid secondary battery. It turned out not.

An object of the present invention is to provide a composite electrode active material capable of imparting excellent battery performance to an all-solid secondary battery by using it as a component contained in an electrode active material layer of the all-solid secondary battery. Further, the present invention uses the composite electrode active material, an electrode composition, an electrode sheet for an all-solid secondary battery and an all-solid secondary battery, and a composite electrode active material and an electrode sheet for an all-solid secondary battery. An object of the present invention is to provide a method for manufacturing an all-solid secondary battery.

As a result of various studies, the present inventor has coated the surface of the active material with a coating layer of an inorganic solid electrolyte and a conductive auxiliary agent as an active material for an all-solid secondary battery, and further obtained the coating layer. By setting the ratio of the number of carbon atoms to the number of lithium atoms in the outer region larger than the ratio of the number of carbon atoms to the number of lithium atoms in the inner region of the coating layer, the electron conduction path and the ion conduction path constructed in this active material are set. It was found that the all-solid-state secondary battery can be provided with excellent battery performance without being interrupted even if the expansion and contraction due to repeated charging and discharging are repeated. The present invention has been further studied based on these findings and has been completed.

That is, the above problem was solved by the following means.
<1>
A composite electrode active material having an active material and a coating layer covering the active material.
The coating layer contains an inorganic solid electrolyte and a conductive auxiliary agent,
A composite electrode active material in which lithium atoms and carbon atoms contained in the coating layer satisfy the relationship defined by the following formula (I) with respect to the number of atoms.
A1 <B1 formula (I)
In the formula, A1 represents the ratio C / Li of the number of carbon atoms to the number of lithium atoms in the region A having a thickness of 0.5 μm outward from the active material contact portion of the coating layer, and B1 is the surface of the coating layer. The ratio C / Li of the number of carbon atoms to the number of lithium atoms in the region B having a thickness of 0.5 μm is shown from the inside to the inside. However, B1 is 99/1 or less.
<2>
The composite electrode according to <1>, wherein the lithium atom and the carbon atom contained in the region C between the regions A and B satisfy the relationship defined by the following formula (IIA) or formula (IIB) with respect to the number of atoms. Active material.
A1 ≤ C1 <B1 equation (IIA)
A1 <C1 ≤ B1 equation (IIB)
In the formula, A1 and B1 are synonymous with A1 and B1 in the above formula (I). C1 indicates the ratio C / Li of the number of carbon atoms to the number of lithium atoms in the region C.
<3>
The composite electrode active material according to <1> or <2>, wherein the conductive auxiliary agent contains fibrous carbon.
<4>
The composite electrode active material according to any one of <1> to <3>, wherein the conductive auxiliary agent present in the region B contains fibrous carbon.
<5>
The composite electrode active material according to any one of <1> to <4>, wherein B1 is 50/50 to 99/1.

<6>
A composition for an electrode containing the composite electrode active material according to any one of <1> to <5> and a dispersion medium.
<7>
The electrode composition according to <6>, which comprises a binder.
<8>
The electrode composition according to <7>, wherein the binder is in the form of particles.

<9>
An electrode sheet for an all-solid-state secondary battery containing the composite electrode active material according to any one of <1> to <5>.
<10>
The electrode sheet for an all-solid-state secondary battery according to <9>, which contains a binder.
<11>
The electrode sheet for an all-solid-state secondary battery according to <10>, wherein the binder is in the form of particles.

<12>
An all-solid-state secondary battery including a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer in this order.
At least one layer of the positive electrode active material layer and the negative electrode active material layer is an all-solid-state secondary layer formed of the electrode sheet for an all-solid-state secondary battery according to any one of <9> to <11>. Next battery.
<13>
The method for producing a composite electrode active material according to any one of <1> to <5>.
It has the following step (1) and the following step (2) to be performed once or multiple times, and the mixing ratio of the inorganic solid electrolyte and the conductive auxiliary agent in the following step (1) and the final step (2) is changed. A method for producing a composite electrode active material, wherein a coating layer satisfying the relationship defined by the above formula (I) is formed on the surface of the active material.
Step (1): Mixing the active material, the inorganic solid electrolyte and the conductive auxiliary agent Step (2): Mixing the mixture obtained in the above step (1) with the inorganic solid electrolyte and the conductive auxiliary agent <14>
A method for producing an electrode sheet for an all-solid-state secondary battery, which comprises forming a film of the electrode composition according to any one of <6> to <8>.
<15>
A method for manufacturing an all-solid-state secondary battery, wherein the all-solid-state secondary battery is manufactured through the manufacturing method according to <14>.

By using the composite electrode active material of the present invention as a component contained in the electrode active material layer of the all-solid-state secondary battery, excellent battery performance can be imparted to the all-solid-state secondary battery. The electrode composition of the present invention containing the composite electrode active material can impart excellent battery performance to the all-solid secondary battery by using it as a constituent material of the electrode active material layer of the all-solid secondary battery. The electrode sheet for an all-solid-state secondary battery of the present invention contains the above-mentioned composite electrode active material, and by using it as an electrode active material layer of the all-solid-state secondary battery, excellent battery performance can be imparted to the all-solid-state secondary battery. Further, the method for producing the composite electrode active material of the present invention, the electrode sheet for the all-solid secondary battery and the all-solid secondary battery is the composite electrode active material of the present invention exhibiting the above-mentioned excellent characteristics, and the electrode for the all-solid secondary battery. Sheets and all-solid secondary batteries can be manufactured.

FIG. 1 is a vertical sectional view schematically showing an all-solid-state secondary battery according to a preferred embodiment of the present invention.

In the present specification, the numerical range represented by using "-" means a range including the numerical values before and after "-" as the lower limit value and the upper limit value.
In the present specification, the indication of a compound (for example, when referred to as a compound at the end) is used to mean that the compound itself, its salt, and its ions are included. In addition, it is meant to include a derivative which has been partially changed, such as by introducing a substituent, as long as the effect of the present invention is not impaired.

[Composite electrode active material]
The composite electrode active material of the present invention has an active material and a coating layer for coating the active material.
The coating layer contains an inorganic solid electrolyte and a conductive auxiliary agent, and the lithium atoms and carbon atoms contained in the coating layer satisfy the relationship represented by the following formula (I) with respect to the number of atoms.

A1 <B1 (I)

In the formula, A1 refers to the number of lithium atoms in the region A having a thickness of 0.5 μm from the active material contact portion (intersection between the active material and the coating layer) to the outside (opposite side of the active material) of the coating layer. The ratio C / Li of the number of carbon atoms is shown.
B1 shows the ratio C / Li of the number of carbon atoms to the number of lithium atoms in the region B having a thickness of 0.5 μm from the surface to the inside of the coating layer, which is 99/1 or less. Here, since the coating layer is formed of a particulate inorganic solid electrolyte, a conductive additive, or the like, the surface of the coating layer is usually not flat, but in the present invention, the surface of the coating layer is measured in Examples described later. In the method, the composition (Li derived from the coating layer solid electrolyte) is formed on the surface (SEM-EDX (scanning electron microscope-energy dispersive X-ray spectroscopy)) that is not in contact with the active material and is exposed to the voids. It is defined as (a part that changes discontinuously).
C (carbon atom) in the above ratio C / Li is a carbon atom derived from a conductive auxiliary agent, and Li (lithium atom) is a carbon atom derived from an inorganic solid electrolyte.
The ratio C / Li in A1 and B1 is determined by the method described in the section of Examples described later.

The composite electrode active material of the present invention exhibits sufficient electron conductivity and ionic conductivity (an electron conduction path and an ionic conduction path are constructed) by the above configuration. Moreover, the electron conductivity and the ionic conductivity (both conduction paths) are maintained even if the active material repeatedly expands and contracts due to charging and discharging of the all-solid-state secondary battery.

In the composite electrode active material of the present invention, the coating layer (inorganic solid electrolyte, conductive additive, etc.) is physically (mechanically) adsorbed or adhered to the surface of the active material, or bonded by a chemical bond to the surface. It forms a coating layer of. That is, in the composite electrode active material of the present invention, the active material and the coating layer act as one (preferably coated particles) inextricably linked to solve the problem of the present invention. The coverage of the coating layer on the active material is appropriately set according to the type of the active material, the inorganic solid electrolyte and the conductive auxiliary agent, and both conductivitys. For example, 50% or more is set with respect to the surface area of the active material. Preferably, 70% or more is more preferable, 80% or more is further preferable, and 90% or more is particularly preferable. The upper limit is set to 100% or less. The coverage can be measured by the method described in Examples below.
The thickness of the coating layer is not particularly limited as long as it exceeds 1 μm, but can be, for example, more than 1 μm and 10 μm or less, preferably more than 1 μm and 5 μm or less, and more preferably more than 1 μm and 3 μm or less. The thickness of the coating layer can be measured by the method described in Examples described later.

In the present invention, the coating layer is formed in a state (mixture) in which the inorganic solid electrolyte and the conductive auxiliary agent, which are the contained components (forming components), are mixed. As a result, both an electron conduction path and an ionic conduction path can be constructed on the composite electrode active material (particularly the surface thereof).

As described above, the coating layer is formed of a mixture of an inorganic solid electrolyte and a conductive auxiliary agent, and the ratio C / Li satisfies the relationship defined by the above formula (I). That is, it is one of the preferable embodiments that the concentrations of the inorganic solid electrolyte and the conductive auxiliary agent are unevenly distributed on the inside and the outside of the coating layer, and the concentrations are inclined along the thickness direction. The mode of the concentration gradient is not particularly limited, but may be a gradual gradient or a gradual gradient. Further, the concentration gradient is not limited to the gradient that increases or decreases from the inside to the outside, and includes a region where the concentration is constant, a region where the concentration decreases, or a region where the concentration increases during the inclination of the increase or decrease. May be good.

The above A1 is preferably 45/55 to 1/99, more preferably 35/65 to 1/99, in terms of further improving the high rate characteristics of the all-solid-state secondary battery of the present invention. It is more preferably 20/80 to 5/95.
The above B1 may be 99/1 or less in that sufficient ionic conductivity can be secured, and is 50/50 to 99/1 in terms of further improving the high rate characteristics of the all-solid-state secondary battery of the present invention. It is preferably 70/30 to 99/1, more preferably 85/15 to 95/5.
The difference between A1 and B1 is not particularly limited, but when the ratio of the number of carbon atoms to the number of lithium atoms is expressed as a percentage, it is preferably 5 to 99%, more preferably 35 to 90%. ..

In the composite electrode active material of the present invention, in order to further improve the high rate characteristics of the all-solid-state secondary battery of the present invention, the lithium atoms and carbon atoms contained in the region C between the regions A and B have the following atomic numbers. It is preferable to satisfy the relationship specified by the formula (IIA) or the formula (IIB), and it is preferable to satisfy the relationship specified by the following formula (IIC).

A1 ≤ C1 <B1 equation (IIA)
A1 <C1 ≤ B1 equation (IIB)
A1 <C1 <B1 formula (IIC)

In the formula, A1 and B1 are synonymous with A1 and B1 in the formula (I). C1 indicates the ratio C / Li of the number of carbon atoms to the number of lithium atoms in the region C.

“Region C” has a thickness of 0.5 μm (1 μm in total) from the midpoint of the shortest distance between the active material contact portion and the surface of the coating layer (that is, the thickness of the coating layer) toward the regions A and B, respectively. Means the area having. Therefore, the area C may partially overlap with the area A, and the area C may partially overlap with the area B.
C1 is preferably 30/70 to 70/30, more preferably 35/65 to 65/35, in terms of further improving the high rate characteristics of the all-solid-state secondary battery of the present invention. It is more preferably / 60 to 60/40.
In both equations, the difference between A1 and C1 is not particularly limited, but is preferably 15 to 70% and 20 to 55% when the ratio of the number of carbon atoms to the number of lithium atoms is expressed as a percentage. Is more preferable. Similarly, the difference between C1 and B1 is not particularly limited, but is preferably 15 to 70%, preferably 20 to 55%, when the ratio of the number of carbon atoms to the number of lithium atoms is expressed as a percentage. Is more preferable.

The composite electrode active material of the present invention may have a region other than the above region C between the regions A and B. The number of such regions is preferably 1 to 5, more preferably 1 to 3, and even more preferably 1 to 2. The other regions may be the same as or different from the regions A to C in terms of the ratio C / Li of the number of carbon atoms to the number of lithium atoms. One of the preferred embodiments is an embodiment in which the ratio C / Li gradually increases from the region A to the region B.

Hereinafter, the components contained and the components that can be contained in the composite electrode active material of the present invention will be described.

<Active material>
The composite electrode active material of the present invention is a coating layer containing an inorganic solid electrolyte and a conductive auxiliary agent, which is an active material capable of inserting and releasing ions of a metal belonging to Group 1 or Group 2 of the periodic table (hereinafter, "the present invention". It is coated with a coating layer used in the invention. Examples of the active material include a positive electrode active material and a negative electrode active material, which will be described below.

(Positive electrode active material)
The positive electrode active material is preferably one capable of reversibly inserting and releasing lithium ions. The material is not particularly limited as long as it has the above characteristics, and may be a transition metal oxide, an element that can be composited with Li such as sulfur, or the like.
Among them, as the positive electrode active material, a transition metal oxide having preferably used a transition metal oxide, a transition metal element ^{M a (Co, Ni, Fe} , Mn, 1 or more elements selected from Cu and V) the The thing is more preferable. Further, the 1 (Ia) group elements of the transition metal oxide to elemental ^{M b} (Table metal periodic other than lithium, the elements of the 2 (IIa) group, Al, Ga, In, Ge , Sn, Pb, Elements such as Sb, Bi, Si, P and B) may be mixed. The mixing amount is preferably 0 ~ 30 mol% relative to the amount of the transition metal element ^{M a (100mol%).} That the molar ratio of li / ^{M a} was synthesized were mixed so that 0.3 to 2.2, more preferably.
Specific examples of the transition metal oxide include (MA) a transition metal oxide having a layered rock salt type structure, (MB) a transition metal oxide having a spinel type structure, (MC) a lithium-containing transition metal phosphoric acid compound, and (MD). ) Lithium-containing transition metal halide phosphoric acid compound, (ME) lithium-containing transition metal silicic acid compound, and the like.

(MA) Specific examples of the transition metal oxide having a layered rock salt structure include LiCoO ₂ (lithium cobalt oxide [LCO]), LiNi ₂ O ₂ (lithium nickel oxide), LiNi _0.85 Co _0.10 Al _{0. 05} O ₂ (Lithium Nickel Cobalt Aluminate [NCA]), LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (Lithium Nickel Manganese Cobalt Oxide [NMC]) and LiNi _0.5 Mn _0.5 O ₂ ( Lithium manganese nickel oxide).
(MB) Specific examples of the transition metal oxide having a spinel _{_{_{structure, LiMn 2 O 4 (LMO)}}} , LiCoMnO 4, Li 2 FeMn 3 O 8, Li 2 CuMn 3 O 8, Li 2 CrMn 3 O 8 and Li ₂ Nimn ₃ O ₈ can be mentioned.
Examples of the (MC) lithium-containing transition metal phosphate compound include olivine-type iron phosphate salts such as LiFePO ₄ and Li ₃ Fe ₂ (PO ₄ ) ₃ , iron pyrophosphates such as LiFeP ₂ O ₇ , and LiCoPO _4. Examples thereof include cobalt phosphates of the above, and monoclinic panacicon-type vanadium phosphate salts such as Li ₃ V ₂ (PO ₄ ) ₃ (lithium vanadium phosphate).
(MD) as the lithium-containing transition metal halogenated phosphate compound, for _example, Li 2 FePO ₄ F such fluorinated phosphorus iron _salt, Li 2 MnPO ₄ hexafluorophosphate manganese salts such as F and _Li 2 CoPO ₄ F Fluorophosphate cobalts such as.
Examples of the (ME) lithium-containing transition metal silicic acid compound include Li ₂ FeSiO ₄ , Li ₂ MnSiO ₄ , and Li ₂ CoSiO ₄ .
In the present invention, a transition metal oxide having a (MA) layered rock salt type structure is preferable, and LCO or NMC is more preferable.

The shape of the positive electrode active material is not particularly limited, but is preferably in the form of particles. The particle size (volume average particle size) of the positive electrode active material is not particularly limited. For example, it can be 0.1 to 50 μm, more preferably 0.5 to 20 μm, and even more preferably 1.5 to 15 μm. The particle size of the positive electrode active material particles can be measured in the same manner as the particle size of the following inorganic solid electrolyte. A normal crusher or classifier is used to adjust the positive electrode active material to a predetermined particle size. For example, a mortar, a ball mill, a sand mill, a vibrating ball mill, a satellite ball mill, a planetary ball mill, a swirling airflow type jet mill, a sieve, or the like is preferably used. At the time of pulverization, wet pulverization in which an organic solvent such as water or methanol coexists can also be performed. It is preferable to perform classification in order to obtain a desired particle size. The classification is not particularly limited, and can be performed using a sieve, a wind power classifier, or the like. Both dry and wet classifications can be used.
The positive electrode active material obtained by the firing method may be used after being washed with water, an acidic aqueous solution, an alkaline aqueous solution, or an organic solvent.

The positive electrode active material may contain one kind or two or more kinds.

(Negative electrode active material)
The negative electrode active material is preferably one capable of reversibly inserting and releasing lithium ions. The material is not particularly limited as long as it has the above characteristics, and examples thereof include a carbonaceous material, a metal oxide, a metal composite oxide, a lithium simple substance, a lithium alloy, and a negative electrode active material capable of forming an alloy with lithium. .. Among them, a carbonaceous material, a metal composite oxide or a simple substance of lithium is preferably used from the viewpoint of reliability.

The carbonaceous material used as the negative electrode active material is a material substantially composed of carbon. For example, various synthesis of petroleum pitch, carbon black such as acetylene black (AB), graphite (artificial graphite such as natural graphite and vapor-grown graphite), and PAN (polyacrylonitrile) -based resin or furfuryl alcohol resin. Examples thereof include carbonic materials obtained by firing a resin. Furthermore, various carbon fibers such as PAN-based carbon fibers, cellulose-based carbon fibers, pitch-based carbon fibers, vapor-grown carbon fibers, dehydrated PVA (polypoly alcohol) -based carbon fibers, lignin carbon fibers, graphitic carbon fibers and activated carbon fibers. Kind, mesophase microspheres, graphite whisker, flat graphite and the like can also be mentioned.
These carbonaceous materials can also be divided into non-graphitizable carbonaceous materials (also referred to as hard carbon) and graphite-based carbonaceous materials depending on the degree of graphitization. Further, the carbonaceous material preferably has the plane spacing or density and the size of crystallites described in JP-A-62-22066, JP-A-2-6856, and JP-A-3-45473. The carbonaceous material does not have to be a single material, and a mixture of natural graphite and artificial graphite described in JP-A-5-90844, graphite having a coating layer described in JP-A-6-4516, and the like should be used. You can also.
As the carbonaceous material, hard carbon or graphite is preferably used, and graphite is more preferably used.

The metal or semi-metal element oxide applied as the negative electrode active material is not particularly limited as long as it is an oxide capable of storing and releasing lithium, and is a composite of a metal element oxide (metal oxide) and a metal element. Examples thereof include oxides or composite oxides of metal elements and semi-metal elements (collectively referred to as metal composite oxides) and oxides of semi-metal elements (semi-metal oxides). As these oxides, amorphous oxides are preferable, and chalcogenides, which are reaction products of metal elements and elements of Group 16 of the Periodic Table, are also preferable. In the present invention, the semi-metallic element means an element exhibiting properties intermediate between the metallic element and the non-semi-metallic element, and usually contains 6 elements of boron, silicon, germanium, arsenic, antimony and tellurium, and further selenium. , Polonium and Astatine. Further, "amorphous" means an X-ray diffraction method using CuKα rays, which has a broad scattering band having an apex in a region of 20 ° to 40 ° in 2θ value, and a crystalline diffraction line is used. You may have. The strongest intensity of the crystalline diffraction lines found at the 2θ value of 40 ° to 70 ° is 100 times or less the diffraction line intensity at the apex of the broad scattering band seen at the 2θ value of 20 ° to 40 °. It is preferable that it is 5 times or less, and it is particularly preferable that it does not have a crystalline diffraction line.

Among the compound group consisting of the amorphous oxide and the chalcogenide, the amorphous oxide of the semi-metal element or the chalcogenide is more preferable, and the elements of the groups 13 (IIIB) to 15 (VB) of the periodic table (for example). , Al, Ga, Si, Sn, Ge, Pb, Sb and Bi) alone or a combination of two or more (composite) oxides, or chalcogenides are particularly preferred. Specific examples of preferable amorphous oxides and chalcogenides include, for example, Ga ₂ O ₃ , GeO, PbO, PbO ₂ , Pb ₂ O ₃ , Pb ₂ O ₄ , Pb ₃ O ₄ , Sb ₂ O ₃ , Sb _2. O ₄ , Sb ₂ O ₈ Bi ₂ O ₃ , Sb ₂ O ₈ Si ₂ O ₃ , Sb ₂ O ₅ , Bi ₂ O ₃ , Bi ₂ O ₄ , GeS, PbS, PbS ₂ , Sb ₂ S ₃ or Sb ₂ S ₅ is preferably mentioned.
Examples of the negative electrode active material that can be used in combination with the amorphous oxide negative electrode active material centering on Sn, Si, and Ge include a carbonaceous material capable of occluding and / or releasing lithium ions or lithium metal, lithium alone, and lithium. A negative electrode active material that can be alloyed with an alloy or lithium is preferably used.

It is preferable that the oxide of a metal or a metalloid element, particularly a metal (composite) oxide and the chalcogenide, contains at least one of titanium and lithium as a constituent component from the viewpoint of high current density charge / discharge characteristics. Examples of the lithium-containing metal composite oxide (lithium composite metal oxide) include lithium oxide and the metal (composite) oxide or a composite oxide of the chalcogenide, more specifically, Li ₂ SnO _2. Can be mentioned.
It is also preferable that the negative electrode active material, for example, a metal oxide, contains a titanium element (titanium oxide). Specifically, Li ₄ Ti ₅ O ₁₂ (lithium titanate [LTO]) has excellent rapid charge / discharge characteristics due to small volume fluctuations during storage and release of lithium ions, and electrode deterioration is suppressed and lithium ion secondary It is preferable in that the life of the battery can be improved.

The lithium alloy as the negative electrode active material is not particularly limited as long as it is an alloy usually used as the negative electrode active material of the secondary battery, and examples thereof include a lithium aluminum alloy.

The negative electrode active material that can be alloyed with lithium is not particularly limited as long as it is usually used as the negative electrode active material of the secondary battery. Such an active material has a large expansion and contraction due to charging and discharging, and the battery performance tends to deteriorate as described above. However, in the present invention, the deterioration of the battery performance can be suppressed by coating the negative electrode active material with the coating layer. Examples of such an active material include a negative electrode active material (alloy) having a silicon element or a tin element, and each metal such as Al and In, and a negative negative active material (silicon element) having a silicon element that enables a higher battery capacity. (Containing active material) is preferable, and a silicon element-containing active material having a silicon element content of 50 mol% or more of all the constituent elements is more preferable.
Generally, a negative electrode containing these negative electrode active materials (Si negative electrode containing a silicon element-containing active material, Sn negative electrode containing an active material containing a tin element, etc.) is used as a carbon negative electrode (graphite, acetylene black, etc.). In comparison, more Li ions can be occluded. That is, the occlusal amount of Li ions per unit mass increases. Therefore, the battery capacity can be increased. As a result, there is an advantage that the battery drive time can be lengthened.
Examples of the silicon element-containing active material include silicon materials such as Si and SiOx (0 <x≤1), and silicon-containing alloys containing titanium, vanadium, chromium, manganese, nickel, copper, lanthanum, and the like (for example,). LaSi ₂ , VSi ₂ , La-Si, Gd-Si, Ni-Si) or organized active material (eg LaSi ₂ / Si), as well as other silicon and tin elements such as SnSiO ₃ , SnSiS ₃ Examples include active materials containing. In addition, SiOx itself can be used as a negative electrode active material (semi-metal oxide), and since Si is generated by the operation of an all-solid-state secondary battery, a negative electrode active material that can be alloyed with lithium (its). It can be used as a precursor substance).
Examples of the negative electrode active material having a tin element include Sn, SnO, SnO ₂ , SnS, SnS ₂ , and the active material containing the silicon element and the tin element. Further, a composite oxide with lithium oxide, for example, Li ₂ SnO ₂ can also be mentioned.

In the present invention, the above-mentioned negative electrode active material can be used without particular limitation, but in terms of battery capacity, a negative electrode active material that can be alloyed with silicon is a preferred embodiment as the negative electrode active material. , The above-mentioned silicon material or silicon-containing alloy (alloy containing a silicon element) is more preferable, and it is further preferable to contain silicon (Si) or a silicon-containing alloy.

The chemical formula of the compound obtained by the above firing method can be calculated from the inductively coupled plasma (ICP) emission spectroscopic analysis method as a measuring method and the mass difference of the powder before and after firing as a simple method.

The shape of the negative electrode active material is not particularly limited, but it is preferably in the form of particles. The volume average particle size of the negative electrode active material is not particularly limited, but is preferably 0.1 to 60 μm, more preferably 0.5 to 20 μm, and even more preferably 1.0 to 15 μm. The volume average particle diameter of the negative electrode active material particles can be measured in the same manner as the average particle diameter of the following inorganic solid electrolyte. In order to obtain a predetermined particle size, a normal crusher or classifier is used as in the case of the positive electrode active material.

The negative electrode active material may contain one kind or two or more kinds.

When the composite electrode active material of the present invention is used as the positive electrode active material in the all-solid-state secondary battery, the negative electrode active material layer can also be formed by charging the secondary battery. In this case, instead of the negative electrode active material, metal ions belonging to Group 1 or Group 2 of the periodic table generated in the all-solid-state secondary battery can be used. The negative electrode active material layer can be formed by combining these ions with electrons and precipitating them as a metal.

(Coating of active material)
The surfaces of the positive electrode active material and the negative electrode active material may be surface-coated with another metal oxide. That is, a surface coating formed of another metal oxide may be provided between the active material and the coating layer. Examples of the surface coating agent include metal oxides containing Ti, Nb, Ta, W, Zr, Al, Si or Li. Specific examples include spinel titanate, tantalate oxide, niobate oxide, lithium niobate compound, and the like. Specifically, Li ₄ Ti ₅ O ₁₂ , Li ₂ Ti ₂ O ₅ , LiTaO ₃ , LiNbO ₃ , LiAlO ₂ , Li ₂ ZrO ₃ , Li ₂ WO ₄ , Li ₂ TiO ₃ , Li ₂ B ₄ O ₇ , Li ₃ PO ₄ , Li ₂ MoO ₄ , Li ₃ BO ₃ , LiBO ₂ , Li ₂ CO ₃ , Li ₂ SiO ₃ , SiO ₂ , TiO ₂ , ZrO ₂ , Al ₂ O ₃ , B ₂ O _{3, and the} like.
Further, the surface of the electrode containing the positive electrode active material or the negative electrode active material may be surface-treated with sulfur or phosphorus.
Further, the surface of the particles of the positive electrode active material or the negative electrode active material forming the surface coating may be surface-treated with active light rays or an active gas (plasma or the like) before and after the surface coating.

<Inorganic solid electrolyte>
The coating layer used in the present invention contains an inorganic solid electrolyte.
In the present invention, the inorganic solid electrolyte is an inorganic solid electrolyte having a lithium atom, and the solid electrolyte is a solid electrolyte capable of transferring ions inside the solid electrolyte. Since it does not contain organic substances as the main ionic conductive material, it is an organic solid electrolyte (polymer electrolyte represented by polyethylene oxide (PEO), organic represented by lithium bis (trifluoromethanesulfonyl) imide (LiTFSI), etc. It is clearly distinguished from electrolyte salts). Further, since the inorganic solid electrolyte is a solid in a steady state, it is usually not dissociated or liberated into cations and anions. In this respect, it is clearly distinguished from inorganic electrolyte salts (LiPF ₆ , LiBF ₄ , Lithium bis (fluorosulfonyl) imide (LiFSI), LiCl, etc.) that are dissociated or liberated into cations and anions in the electrolyte or polymer. Will be done. The inorganic solid electrolyte is not particularly limited as long as it has the ionic conductivity of a metal belonging to Group 1 or Group 2 of the periodic table, and is generally one having no electron conductivity. When the all-solid-state secondary battery of the present invention is a lithium-ion battery, the inorganic solid electrolyte preferably has lithium ion ionic conductivity.
As the inorganic solid electrolyte, a solid electrolyte material usually used for an all-solid secondary battery can be appropriately selected and used. Examples of the inorganic solid electrolyte include (i) a sulfide-based inorganic solid electrolyte, (ii) an oxide-based inorganic solid electrolyte, (iii) a halide-based inorganic solid electrolyte, and (iV) a hydride-based solid electrolyte. A sulfide-based inorganic solid electrolyte is preferable from the viewpoint of being able to form a better interface between the and the inorganic solid electrolyte, and further, from the viewpoint of enhancing the adhesion between the coating layer and the active material in mixing with a mixer described later. ..

(I) Sulfide-based inorganic solid electrolyte The sulfide-based inorganic solid electrolyte contains a sulfur atom, has ionic conductivity of a metal belonging to Group 1 of the Periodic Table, and has electronic insulation. Is preferable. The sulfide-based inorganic solid electrolyte preferably contains at least Li, S and P as elements and has lithium ion conductivity, but other than Li, S and P may be used depending on the purpose or case. It may contain elements.

Examples of the sulfide-based inorganic solid electrolyte include a lithium ion conductive inorganic solid electrolyte satisfying the composition represented by the following formula (S1).

L _a1 M _b1 P _c1 S _d1 A _e1 (S1)

In the formula, L represents an element selected from Li, Na and K, and at least a part of L represents Li. M represents an element selected from B, Zn, Sn, Si, Cu, Ga, Sb, Al and Ge. A represents an element selected from I, Br, Cl and F. a1 to e1 indicate the composition ratio of each element, and a1: b1: c1: d1: e1 satisfy 1 to 12: 0 to 5: 1: 2 to 12: 0 to 10. a1 is preferably 1 to 9, more preferably 1.5 to 7.5. b1 is preferably 0 to 3, more preferably 0 to 1. The d1 is preferably 2.5 to 10, more preferably 3.0 to 8.5. e1 is preferably 0 to 5, more preferably 0 to 3.

The composition ratio of each element can be controlled by adjusting the blending amount of the raw material compound when producing the sulfide-based inorganic solid electrolyte as described below.

The sulfide-based inorganic solid electrolyte may be non-crystal (glass) or crystallized (glass-ceramic), or only a part thereof may be crystallized. For example, Li-PS-based glass containing Li, P and S, or Li-PS-based glass ceramics containing Li, P and S can be used.
Sulfide-based inorganic solid electrolytes include, for example, lithium sulfide (Li ₂ S), phosphorus sulfide (for example, diphosphorus pentasulfide (P ₂ S ₅ )), simple phosphorus, simple sulfur, sodium sulfide, hydrogen sulfide, and lithium halide (for example). It can be produced by the reaction of at least two or more raw materials in sulfides of LiI, LiBr, LiCl) and the element represented by M (for example, SiS ₂ , SnS, GeS ₂ ).

In Li-P-S based glass and Li-P-S based glass ceramics, the ratio of Li ₂ S and _P 2 _{S 5} _is, Li 2 _S: at a molar ratio of P 2 _{S 5,} preferably 60: 40 ~ It is 90:10, more preferably 68:32 to 78:22. By setting the ratio of Li ₂ S and P ₂ S ₅ in this range, the lithium ion conductivity can be made high. Specifically, the lithium ion conductivity can be preferably 1 × 10 ^-4 S / cm or more, and more preferably 1 × 10 ^-3 S / cm or more. There is no particular upper limit, but it is practical that it is 1 × 10 ^-1 S / cm or less.

As an example of a specific sulfide-based inorganic solid electrolyte, an example of combining raw materials is shown below. For _{_{_{_{example, Li 2 S-P 2 S}}}} 5, Li 2 S-P 2 S 5 -LiCl, Li 2 S-P 2 S 5 -H 2 S, Li 2 S-P 2 S 5 -H 2 S-LiCl, Li ₂ S-LiI-P ₂ S ₅ , Li ₂ S-LiI-Li ₂ O-P ₂ S ₅ , Li ₂ S-LiBr-P ₂ S ₅ , Li ₂ S-Li ₂ O-P ₂ S ₅ , Li ₂ S-Li ₃ PO _4- P ₂ S ₅ , Li ₂ S-P ₂ S _5- P ₂ O ₅ , Li ₂ S-P ₂ S _5- SiS ₂ , Li ₂ S-P ₂ S _5- SiS _2- LiCl, Li ₂ S-P ₂ S _5- SnS, Li ₂ S-P ₂ S _5- Al ₂ S ₃ , Li ₂ S-GeS ₂ , Li ₂ S-GeS _2- ZnS, Li ₂ S-Ga ₂ S ₃ , Li ₂ S-GeS _2- Ga ₂ S ₃ , Li ₂ S-GeS _2- P ₂ S ₅ , Li ₂ S-GeS _2- Sb ₂ S ₅ , Li ₂ S-GeS _2- Al ₂ S ₃ , Li ₂ S-SiS ₂ , Li ₂ S-Al ₂ S ₃ , Li ₂ S-SiS _2- Al ₂ S ₃ , Li ₂ S-SiS _2- P ₂ S ₅ , Li ₂ S-SiS _2- P Examples thereof include ₂ S _5- LiI, Li ₂ S-SiS _2- LiI, Li ₂ S-SiS ₂ -Li ₄ SiO ₄ , Li ₂ S-SiS ₂ -Li ₃ PO ₄ , Li ₁₀ GeP ₂ S ₁₂ . However, the mixing ratio of each raw material does not matter. As a method for synthesizing a sulfide-based inorganic solid electrolyte material using such a raw material composition, for example, an amorphization method can be mentioned. Examples of the amorphization method include a mechanical milling method, a solution method and a melt quenching method. This is because processing at room temperature is possible and the manufacturing process can be simplified.

(Ii) Oxide-based inorganic solid electrolyte The oxide-based inorganic solid electrolyte contains lithium atoms and oxygen atoms, has ionic conductivity of a metal belonging to Group 1 of the Periodic Table, and has electron insulation properties. It is preferable to have.
The oxide-based inorganic solid electrolyte preferably has an ionic conductivity of 1 × 10 ^-6 S / cm or more, more preferably 5 × 10 ^-6 S / cm or more, and 1 × 10 ^-5 S / cm or more. It is particularly preferable that it is / cm or more. The upper limit is not particularly limited, but it is practical that it is 1 × 10 ^-1 S / cm or less.

As a specific compound example, for example, Li _xa La _ya TiO ₃ [xa satisfies 0.3 ≦ xa ≦ 0.7, and ya satisfies 0.3 ≦ ya ≦ 0.7. (LLT); Li _xb _Layb Zr _zb M ^bb _mb _Onb (M ^bb is one or more elements selected from Al, Mg, Ca, Sr, V, Nb, Ta, Ti, Ge, In and Sn. Xb satisfies 5 ≦ xb ≦ 10, yb satisfies 1 ≦ yb ≦ 4, zb satisfies 1 ≦ zb ≦ 4, mb satisfies 0 ≦ mb ≦ 2, and nb satisfies 5 ≦ nb ≦ 20. Satisfies.); Li _xc _Byc M ^cc _zc _Onc (M ^cc is one or more elements selected from C, S, Al, Si, Ga, Ge, In and Sn. Xc is 0 <xc ≦ 5 , Yc satisfies 0 <yc ≦ 1, zc satisfies 0 <zc ≦ 1, nc satisfies 0 <nc ≦ 6); Li _xd (Al, Ga) _yd (Ti, Ge) _zd Si. _ad P _md O _nd (xd satisfies 1 ≦ xd ≦ 3, yd satisfies 0 ≦ yd ≦ 1, zd satisfies 0 ≦ zd ≦ 2, ad satisfies 0 ≦ ad ≦ 1, md is 1 ≦ met md ≦ 7, nd satisfies _{3 ≦ nd ≦ 13);.} Li (3-2xe) M ee xe D ee O (xe represents a number of 0 to ^{0.1, M ee} divalent ^{.D ee} representing the metal atom represents a combination of halogen atom or two or more halogen _{_{_{atoms);. Li xf Si yf O}}} zf (xf satisfies 1 ≦ xf ≦ 5, yf satisfies 0 <yf ≦ 3 , zf satisfies _{1 ≦ zf ≦ 10);.} Li xg S yg O zg (xg satisfies 1 ≦ xg ≦ 3, yg satisfies 0 <yg ≦ 2, zg satisfies 1 ≦ zg ≦ 10. ); Li ₃ BO ₃ ; Li ₃ BO _3- Li ₂ SO ₄ ; Li ₂ O-B ₂ O _3- P ₂ O ₅ ; Li ₂ O-SiO ₂ ; Li ₆ BaLa ₂ Ta ₂ O ₁₂ ; Li ₃ PO _{(4-3 / 2w)} N _w (w is w <1); Li _3.5 Zn _0.25 GeO ₄ having a LISION (Lithium super ionic controller) type crystal structure; La _0.55 having a perovskite type crystal structure Li _0.35 TiO ₃ ; LiTi ₂ P ₃ O ₁₂ having a NASICON (Naturium super ionic controller) type crystal structure; Li _{1 + xh + yh} (Al, Ga) _xh (Ti, Ge) _2-xh _Sihy _3-yh O ₁₂ (xh satisfies 0 ≦ xh ≦ 1, yh satisfies 0 ≦ yh ≦ 1. ); Examples thereof include Li ₇ La ₃ Zr ₂ O ₁₂ (LLZ) having a garnet-type crystal structure.
Phosphorus compounds containing Li, P and O are also desirable. For example, lithium phosphate (Li ₃ PO ₄ ); LiPON in which a part of the oxygen atom of lithium phosphate is replaced with nitrogen; LiPOD ¹ (D ¹ is preferably Ti, V, Cr, Mn, Fe, Co, Ni). , Cu, Zr, Nb, Mo, Ru, Ag, Ta, W, Pt and one or more elements selected from Au) and the like.
Further, LiA ¹ ON (A ¹ is one or more elements selected from Si, B, Ge, Al, C and Ga) and the like can also be preferably used.

(Iii) Halide-based inorganic solid electrolyte The halide-based inorganic solid electrolyte contains halogen atoms, has the conductivity of ions of metals belonging to Group 1 or Group 2 of the Periodic Table, and has electrons. Insulating compounds are preferred.
The halide-based inorganic solid electrolyte is not particularly limited, and examples thereof include compounds such as Li ₃ YBr ₆ and Li ₃ YCl ₆ described in LiCl, LiBr, LiI, ADVANCED MATERIALS, 2018, _30, 1803075. Of these, Li ₃ YBr ₆ and Li ₃ YCl ₆ are preferable.

(IV) Hydride-based Inorganic Solid Electrolyte The hydride-based inorganic solid electrolyte contains a hydrogen atom, has ionic conductivity of a metal belonging to Group 1 or Group 2 of the Periodic Table, and is electronically insulated. A compound having a property is preferable.
The hydride-based inorganic solid electrolyte is not particularly limited, and examples thereof include LiBH ₄ , Li ₄ (BH ₄ ) ₃ I, and ₃ LiBH _4- LiCl.

The inorganic solid electrolyte is preferably particles. In this case, the particle size (volume average particle size) of the inorganic solid electrolyte is not particularly limited, but is preferably 0.01 μm or more, and more preferably 0.1 μm or more. The upper limit is preferably 100 μm or less, and more preferably 50 μm or less.
In the present invention, the particle size of the inorganic solid electrolyte is preferably determined in consideration of the particle size of the active material and the conductive additive according to the surface coating state of the active material and the like. Within the above range, the particle size of the inorganic solid electrolyte forming the coating layer is preferably 0.1 to 5 μm, more preferably 0.1 to 3 μm, and preferably 0.2 to 1 μm. More preferred.
The particle size of the inorganic solid electrolyte is preferably smaller than that of the active material, and the difference from the particle size of the active material is not particularly limited, but is preferably 0.5 to 10 μm, preferably 0.8 to 5 μm, for example. More preferably.
The particle size of the inorganic solid electrolyte is measured by the following procedure. Inorganic solid electrolyte particles are prepared by diluting 1% by mass of a dispersion in a 20 mL sample bottle with water (heptane in the case of a water-unstable substance). The diluted dispersed sample is irradiated with 1 kHz ultrasonic waves for 10 minutes, and immediately after that, it is used for the test. Using this dispersion sample, data was captured 50 times using a laser diffraction / scattering particle size distribution measuring device LA-920 (trade name, manufactured by HORIBA) at a temperature of 25 ° C. using a measuring quartz cell. Obtain the volume average particle size. For other detailed conditions, etc., refer to the description of JIS Z 8828: 2013 “Particle size analysis-Dynamic light scattering method” as necessary. Five samples are prepared for each level and the average value is adopted.

The inorganic solid electrolyte may contain one kind or two or more kinds.
The content of the inorganic solid electrolyte in the coating layer is not particularly limited, and is set within a range that satisfies the relationship defined by the above formula (I). For example, it is preferably 15 to 99% by mass, more preferably 20 to 95% by mass, based on the total mass of the coating layer.

<Conductive aid>
The coating layer used in the present invention appropriately contains a conductive auxiliary agent.
The conductive auxiliary agent is not particularly limited as long as it is a substance containing a carbon atom, and a material known as a general conductive auxiliary agent can be used. For example, electron conductive materials such as natural graphite, artificial graphite and other graphite, acetylene black, ketjen black, furnace black and other carbon blacks, needle coke and other amorphous carbon, vapor-grown carbon fibers or carbon nanotubes. It may be a fibrous carbon such as graphene or fullerene, or a conductive polymer such as polyaniline, polypyrrole, polythiophene, polyacetylene, or polyphenylene derivative may be used. In the present invention, a usual conductive auxiliary agent containing no carbon atom such as metal powder such as copper and nickel and metal fiber can be used in combination with the conductive auxiliary agent containing these carbon atoms.
In the present invention, the conductive auxiliary agent means one that does not insert and release Li when the battery is charged and discharged, and does not function as an active material. Therefore, among the conductive auxiliary agents, those that can function as active materials in the active material layer when the battery is charged and discharged are classified as active materials instead of conductive auxiliary agents. Whether or not the battery functions as an active material when it is charged and discharged is not unique and is determined by the combination with the active material.

The shape of the conductive auxiliary agent is not particularly limited, but for example, it is indefinite, particulate or fibrous, preferably particulate or fibrous, and more preferably fibrous. The coating layer used in the present invention preferably contains fibrous carbon. It is preferable that the shapes of the conductive auxiliaries contained in the regions A and B of the coating layer used in the present invention are different, and in order to further improve the high rate characteristics of the all-solid-state secondary battery, the conductive auxiliaries contained in the region B are fibers. It is preferable that the conductive auxiliary agent contained in the region A is in the form of particles, and the conductive auxiliary agent contained in the region B is preferably in the form of fibers.

The volume average particle size of the particulate or fibrous conductive auxiliary agent is preferably determined in consideration of the particle size of the active material and the conductive auxiliary agent according to the surface coating state of the active material and the like. It is preferably 1 to 900 nm, more preferably 5 to 800 nm, and even more preferably 10 to 500 nm. The particle size of the conductive auxiliary agent is preferably smaller than that of the active material, and the difference from the particle size of the active material is not particularly limited, but is preferably 0.1 to 50 μm, for example, 1 to 15 μm. Is more preferable.
The volume average particle diameter of the particulate or fibrous conductive auxiliary agent can be measured in the same manner as the average particle diameter of the inorganic solid electrolyte.

The aspect ratio of the particulate conductive auxiliary agent is preferably 0.5 to 1.5, more preferably 0.8 to 1.2. On the other hand, the aspect ratio of the fibrous conductive auxiliary agent is preferably 2 to 10000, more preferably 10 to 1000. The aspect ratio is determined by, for example, by observing the shape on an SEM image, the line segment having the maximum length among the line segments passing through the center of the conductive auxiliary agent is set as the maximum major axis, and the width orthogonal to the maximum major axis / maximum major axis is used. Can be calculated. The aspect ratio is an arithmetic mean value of 80% of the total number of conductive auxiliaries as 100%.

The conductive auxiliary agent may contain one kind or two or more kinds.
The content of the conductive auxiliary agent in the coating layer is not particularly limited, and is set within a range that satisfies the relationship defined by the above formula (I). For example, it is preferably 5 to 95% by mass, more preferably 10 to 80% by mass, based on the total mass of the coating layer.

<Components other than inorganic solid electrolytes and conductive aids>
The coating layer may contain an inorganic solid electrolyte and a conductive auxiliary agent, and may contain components other than the inorganic solid electrolyte and the conductive auxiliary agent as long as the effects of the present invention are not impaired. The components other than the inorganic solid electrolyte and the conductive auxiliary agent are not particularly limited, but include an ion conductive substance such as a lithium salt or a lithium ion conductive polymer, an electron conductive substance other than the conductive auxiliary agent, and an electrode composition described later. Other components may be mentioned. The coating layer preferably contains no lithium ion conductive polymer (for example, the content in the coating layer is 5% by mass or less).
The content of the above components in the coating layer is not particularly limited. In particular, the content of the component that does not exhibit ionic conductivity and electron conductivity is preferably 5% by mass or less, more preferably 3% by mass or less, and further preferably 1% by mass or less in the coating layer.

(Manufacturing method of composite electrode active material)
The method for producing the composite electrode active material of the present invention is not particularly limited, and examples thereof include a high-speed airflow impact method, a rolling flow coating method (sol-gel method), and a mixing method, and the mixing method is preferable.
The method for shifting the ratio C / Li can be applied without particular limitation to a known method. For example, coating by a high-speed airflow impact method by changing the mixing ratio of the inorganic solid electrolyte and the conductive auxiliary agent. Examples include a method of performing rolling flow coating or mixing multiple times.
As a preferable production method, the following step (1) and the following step (2) performed once or a plurality of times are included, and the mixing of the inorganic solid electrolyte and the conductive auxiliary agent in the step (1) and the final step (2) is performed. Examples thereof include a method of forming a coating layer satisfying the relationship defined by the above formula (I) on the surface of the active material by changing the ratio.

Step (1): Step of mixing the active material, the inorganic solid electrolyte and the conductive auxiliary agent Step (2): Step of mixing the mixture obtained in the step (1) with the inorganic solid electrolyte and the conductive auxiliary agent.

The number of times the step (2) is performed is not particularly limited as long as it is one or more times, and may be, for example, three times. Considering productivity and the like, 1 to 4 times is preferable, and 1 to 3 times is more preferable.
The inorganic solid electrolyte and the conductive auxiliary agent used in the step (2) are materials for newly forming the coating layer, and may be of the same type as the inorganic solid electrolyte and the conductive auxiliary agent (cover layer formed) used in the immediately preceding step. It may be different.
The mixing ratio of the inorganic solid electrolyte and the conductive additive (corresponding to the content in the coating layer) to be mixed in the step (2) is such that the mixing ratio of the above step (2) to be performed last is the mixing ratio of the step (1). It may be different, and may be different for each process. This change in the mixing ratio is appropriately set according to the mode of the concentration gradient. The mixing ratio is usually set to a value that satisfies the ratio C / Li of A1, B1, C1 and other regions in each of the above formulas.

The mixing method in both steps is not particularly limited, and the method described in the method for preparing the electrode composition described later can be applied. One example thereof is a method of mixing an active material or a mixture obtained in the immediately preceding step with an inorganic solid electrolyte and a conductive additive in a ball mill for, for example, 5 to 180 minutes. Specifically, a method described in Examples described later can be mentioned.

[Composition for electrodes]
The electrode composition of the present invention contains the composite electrode active material of the present invention and a dispersion medium. The electrode composition of the present invention is preferably a slurry in which the composite electrode active material is dispersed in a dispersion medium.
The content of the composite electrode active material in the electrode composition is preferably 70% by mass or more, more preferably 80% by mass or more, and more preferably 90% by mass or more, based on the total solid content contained in the electrode composition. It is more preferably 95% by mass or more, and may be 100% by mass.
The electrode composition of the present invention can be preferably used as an electrode sheet for an all-solid-state secondary battery or a molding material for an active material layer of an all-solid-state secondary battery.

In the present specification, the solid content (solid component) means a component that does not volatilize or evaporate and disappear when the electrode composition is dried at 170 ° C. for 6 hours under an atmospheric pressure of 1 mmHg and a nitrogen atmosphere. Typically, it refers to a component other than the dispersion medium described later.

The composition for electrodes of the present invention is not particularly limited, but the water content (also referred to as water content) is preferably 500 ppm or less, more preferably 200 ppm or less, and further preferably 100 ppm or less. It is preferably 50 ppm or less, and particularly preferably 50 ppm or less. When the water content of the electrode composition is low, deterioration of the inorganic solid electrolyte can be suppressed. The water content indicates the amount of water contained in the electrode composition (mass ratio to the electrode composition). Specifically, the water content is filtered through a 0.02 μm membrane filter, and Karl Fischer titration is used. It shall be the measured value.

<Dispersion medium>
The dispersion medium (dispersion medium) contained in the electrode composition of the present invention may be any one that disperses or dissolves the contained solid content. Examples of the dispersion medium include various organic solvents. Examples of the organic solvent include alcohol compounds, ether compounds, amide compounds, amine compounds, ketone compounds, aromatic compounds, aliphatic compounds, nitrile compounds, ester compounds and the like.

Specific examples of each of the above solvents are shown below.
Examples of the alcohol compound include methyl alcohol, ethyl alcohol, 1-propyl alcohol, 2-propyl alcohol, 2-butanol, ethylene glycol, propylene glycol, glycerin, 1,6-hexanediol, cyclohexanediol, sorbitol, xylitol, and 2 -Methyl-2,4-pentanediol, 1,3-butanediol, 1,4-butanediol can be mentioned.

Examples of the ether compound include alkylene glycol alkyl ethers (ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, diethylene glycol, dipropylene glycol, propylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol, polyethylene glycol, propylene glycol monomethyl ether, and dipropylene glycol. Monomethyl ether, tripropylene glycol monomethyl ether, diethylene glycol monobutyl ether, diethylene glycol monobutyl ether, etc.), dialkyl ether (dimethyl ether, diethyl ether, diisopropyl ether, dibutyl ether, etc.), cyclic ether (tetrahydrofuran, dioxane (1,2-, 1,3, etc.) -And each isomer of 1,4-), etc.) can be mentioned.

Examples of the amide compound include N, N-dimethylformamide, N-methyl-2-pyrrolidone, 2-pyrrolidinone, 1,3-dimethyl-2-imidazolidinone, 2-pyrrolidinone, ε-caprolactam, formamide, and N-. Examples thereof include methylformamide, acetamide, N-methylacetamide, N, N-dimethylacetamide, N-methylpropanamide, hexamethylphosphoric triamide and the like.

Examples of the amine compound include triethylamine, diisopropylethylamine, tributylamine and the like.
Examples of the ketone compound include acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and diisobutyl ketone.
Examples of the aromatic compound include aromatic hydrocarbon compounds such as benzene, toluene and xylene.
Examples of the aliphatic compound include aliphatic hydrocarbon compounds such as hexane, heptane, octane, and decane.
Examples of the nitrile compound include acetonitrile, propyronitrile, isobutyronitrile and the like.
Examples of the ester compound include ethyl acetate, butyl acetate, propyl acetate, butyl butyrate, butyl pentanate and the like.
Examples of the non-aqueous dispersion medium include the above aromatic compounds and aliphatic compounds.

In the present invention, among them, ether compounds, ketone compounds, aromatic compounds, aliphatic compounds and ester compounds are preferable, and ketone compounds, aliphatic compounds or ester compounds are more preferable. In the present invention, it is preferable to further select the above-mentioned specific organic solvent by using a sulfide-based inorganic solid electrolyte. By selecting this combination, the sulfide-based inorganic solid electrolyte can be handled stably because it does not contain a functional group that is active with respect to the sulfide-based inorganic solid electrolyte. In particular, a combination of a sulfide-based inorganic solid electrolyte and an aliphatic compound is preferable.

The dispersion medium preferably has a boiling point of 50 ° C. or higher at normal pressure (1 atm), and more preferably 70 ° C. or higher. The upper limit is preferably 250 ° C. or lower, and more preferably 220 ° C. or lower.
The dispersion medium may contain one kind alone or two or more kinds.

In the present invention, the content of the dispersion medium in the electrode composition is not particularly limited and can be appropriately set. For example, in the composition for electrodes, 20 to 99% by mass is preferable, 25 to 70% by mass is more preferable, and 30 to 60% by mass is particularly preferable.

<Binder>
The electrode composition of the present invention may contain a binder. The binder may be contained in any form, for example, in an electrode composition, an electrode sheet for an all-solid-state secondary battery, or an all-solid-state secondary battery, the binder may be in the form of particles or in an indefinite shape. May be good. The binder is preferably contained in the form of polymer particles. More preferably, it is contained in the form of resin particles containing a macromonomer component.
When the binder used in the present invention is polymer particles, the polymer forming the polymer particles is not particularly limited.
This binder is not particularly limited, and for example, the form of particles made of the following polymer is preferable.

Examples of the fluoropolymer include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), and a copolymer of polyvinylidene fluoride and hexafluoropropylene (PVdF-HFP).
Examples of the hydrocarbon-based thermoplastic polymer include polyethylene, polypropylene, styrene-butadiene rubber (SBR), hydrogenated styrene-butadiene rubber (HSBR), butylene rubber, acrylonitrile-butadiene rubber, polybutadiene, and polyisoprene.
Examples of the acrylic polymer include various (meth) acrylic monomers, (meth) acrylamide monomers, and copolymers of the monomers constituting these polymers (preferably copolymers of acrylic acid and methyl acrylate). Be done.
Further, a copolymer (copolymer) with other vinyl-based monomers is also preferably used. For example, a copolymer of methyl (meth) acrylate and styrene, a copolymer of methyl (meth) acrylate and acrylonitrile, and a copolymer of butyl (meth) acrylate, acrylonitrile and styrene can be mentioned. In the present invention, the copolymer may be either a statistical copolymer or a periodic copolymer, and a block copolymer is preferable.
Examples of other polymers include polyurethane, polyurea, polyamide, polyimide, polyester, polyether, polycarbonate, cellulose derivative and the like.
Among these, acrylic polymers, polyurethanes, polyamides and polyimides are preferable, acrylic polymers, polyurethanes and polyamides are more preferable, and acrylic polymers are particularly preferable.

As the polymer constituting the binder, a polymer synthesized or prepared by a conventional method may be used, or a commercially available product may be used.
The binder may contain one kind or two or more kinds.

When the electrode composition contains a binder, the content of the binder in the electrode composition is solid in consideration of reduction of interfacial resistance and maintenance of reduced interfacial resistance when used in an all-solid-state secondary battery. Of the 100% by mass of the components, 0.01% by mass or more is preferable, 0.1% by mass or more is more preferable, and 1% by mass or more is further preferable. From the viewpoint of battery characteristics, the upper limit is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less.

<Lithium salt>
The electrode composition of the present invention preferably contains a lithium salt (supporting electrolyte).
As the lithium salt, the lithium salt usually used for this kind of product is preferable, and there is no particular limitation. For example, the lithium salt described in paragraphs 882 to 985 of JP2015-088486 is preferable.
When the composition for an electrode of the present invention contains a lithium salt, the content of the lithium salt is preferably 0.1 part by mass or more, more preferably 5 parts by mass or more, based on 100 parts by mass of the composite electrode active material. The upper limit is preferably 50 parts by mass or less, and more preferably 20 parts by mass or less.

<Dispersant>
The composition for electrodes of the present invention may contain a dispersant. As the dispersant, those usually used for all-solid-state secondary batteries can be appropriately selected and used. In general, compounds intended for particle adsorption, steric repulsion and / or electrostatic repulsion are preferably used.

<Other additives>
In the electrode composition of the present invention, as components other than the above components, an ionic liquid, a thickener, a cross-linking agent (such as one that undergoes a cross-linking reaction by radical polymerization, condensation polymerization, or ring-opening polymerization), polymerization, etc. It can contain initiators (such as those that generate acids or radicals by heat or light), defoaming agents, leveling agents, dehydrating agents, antioxidants and the like. The ionic liquid is contained in order to further improve the ionic conductivity, and known ones can be used without particular limitation.

(Preparation of composition for electrodes)
The electrode composition of the present invention can be prepared as a mixture by mixing a composite electrode active material, a dispersion medium, and optionally a binder, a lithium salt, and any other components in various commonly used mixers, for example. It can be prepared preferably as a slurry.
The mixing method is not particularly limited, and the mixture may be mixed all at once or sequentially. The mixing environment is not particularly limited, and examples thereof include under dry air and under an inert gas.

[Electrode sheet for all-solid-state secondary battery]
The electrode sheet for an all-solid-state secondary battery of the present invention is a sheet-like molded body capable of forming an electrode active material layer of an all-solid-state secondary battery, and is preferably used for an electrode or a laminate of an electrode and a solid electrolyte layer. Be done.

The electrode sheet for an all-solid-state secondary battery of the present invention (also simply referred to as "electrode sheet") may be an electrode sheet having an active material layer, and the active material layer is formed on a base material (current collector). The sheet may be a sheet that does not have a base material and is formed from an active material layer. This electrode sheet is usually a sheet having a current collector and an active material layer, but an embodiment having a current collector, an active material layer and a solid electrolyte layer in this order, and a current collector, an active material layer and a solid electrolyte. An embodiment having a layer and an active material layer in this order is also included. The electrode sheet of the present invention may have the other layers described above. The layer thickness of each layer constituting the electrode sheet of the present invention is the same as the layer thickness of each layer described in the all-solid-state secondary battery described later.

In the sheet for an all-solid-state secondary battery of the present invention, at least one layer of the active material layer contains the composite electrode active material of the present invention. In the active material layer containing the composite electrode active material of the present invention, most of the composite electrode active material maintains the state of being coated with the active material by the coating layer, and further, the relationship defined by the above formula (I) is greatly increased. It is maintained without damage. A part of the inorganic solid electrolyte and the conductive auxiliary agent forming the coating layer may be removed from the coating layer and exist independently of the composite electrode active material as long as the effects of the present invention are not impaired. As a result, when an all-solid-state secondary battery is manufactured using the electrode sheet for the all-solid-state secondary battery of the present invention, excellent battery performance is exhibited.

[Manufacturing method of electrode sheet for all-solid-state secondary battery]
The method for producing the electrode sheet for an all-solid-state secondary battery of the present invention is not particularly limited, and the electrode sheet can be produced by forming an active material layer using the electrode composition of the present invention. For example, preferably, a method of forming a film (coating and drying) on the current collector (which may be via another layer) to form a layer (coating and drying layer) composed of the electrode composition can be mentioned. As a result, an electrode sheet for an all-solid-state secondary battery having a current collector and a coating dry layer can be produced. Here, the coating dry layer is a layer formed by applying the electrode composition of the present invention and drying the dispersion medium (that is, the electrode composition of the present invention is used, and the electrode of the present invention is used. A layer having a composition obtained by removing the dispersion medium from the composition for use). In the active material layer, the dispersion medium may remain as long as the effect of the present invention is not impaired, and the residual amount may be, for example, 3% by mass or less in each layer.
In the method for manufacturing an electrode sheet for an all-solid-state secondary battery of the present invention, each step such as coating and drying will be described in the following method for manufacturing an all-solid-state secondary battery.

In the method for producing an electrode sheet for an all-solid-state secondary battery of the present invention, the coating dry layer obtained as described above can also be pressurized. The pressurizing conditions and the like will be described later in the method for manufacturing an all-solid-state secondary battery.
Further, in the method for producing an electrode sheet for an all-solid-state secondary battery of the present invention, the base material, the protective layer (particularly the release sheet) and the like can be peeled off.

[All-solid-state secondary battery]
The all-solid secondary battery of the present invention has a positive electrode active material layer, a negative electrode active material layer facing the positive electrode active material layer, and a solid electrolyte layer arranged between the positive electrode active material layer and the negative electrode active material layer. Have. The positive electrode active material layer is preferably formed on the positive electrode current collector to form the positive electrode. The negative electrode active material layer is preferably formed on the negative electrode current collector to form the negative electrode.
It is preferable that at least one layer of the negative electrode active material layer and the positive electrode active material layer contains the composite electrode active material of the present invention, and the negative electrode active material layer and the positive electrode active material layer contain the composite electrode active material. Most of the composite electrode active material in the active material layer containing the composite electrode active material of the present invention maintains the state of being coated with the active material by the coating layer, and further, the relationship defined by the above formula (I) is greatly increased. It is maintained without damage. A part of the inorganic solid electrolyte and the conductive auxiliary agent forming the coating layer may be removed from the coating layer and exist independently of the composite electrode active material as long as the effects of the present invention are not impaired. Further, the active material layer is preferably contained in the same component species and the content ratio thereof in the solid content of the electrode composition of the present invention. If one of the active material layers is not formed of the electrode composition of the present invention, a known material can be used.
The thicknesses of the negative electrode active material layer, the solid electrolyte layer, and the positive electrode active material layer are not particularly limited. The thickness of each layer is preferably 10 to 1,000 μm, more preferably 20 μm or more and less than 500 μm, respectively, in consideration of the dimensions of a general all-solid-state secondary battery. In the all-solid-state secondary battery of the present invention, the thickness of at least one of the positive electrode active material layer and the negative electrode active material layer is more preferably 50 μm or more and less than 500 μm.
The positive electrode active material layer and the negative electrode active material layer may each have a current collector on the opposite side of the solid electrolyte layer.

[Case]
Depending on the application, the all-solid-state secondary battery of the present invention may be used as an all-solid-state secondary battery with the above structure, but in order to form a dry battery, it should be further enclosed in a suitable housing. Is preferable. The housing may be made of metal or resin (plastic). When a metallic material is used, for example, one made of aluminum alloy or stainless steel can be mentioned. It is preferable that the metallic housing is divided into a positive electrode side housing and a negative electrode side housing, and electrically connected to the positive electrode current collector and the negative electrode current collector, respectively. It is preferable that the housing on the positive electrode side and the housing on the negative electrode side are joined and integrated via a gasket for preventing a short circuit.

The all-solid-state secondary battery according to the preferred embodiment of the present invention will be described below with reference to FIG. 1, but the present invention is not limited thereto.

FIG. 1 is a schematic cross-sectional view showing an all-solid-state secondary battery (lithium ion secondary battery) according to a preferred embodiment of the present invention. The all-solid-state secondary battery 10 of the present embodiment has a negative electrode current collector 1, a negative electrode active material layer 2, a solid electrolyte layer 3, a positive electrode active material layer 4, and a positive electrode current collector 5 in this order when viewed from the negative electrode side. .. Each layer is in contact with each other and has an adjacent structure. By adopting such a structure, during charging, electrons (e ⁻ ) are supplied to the negative electrode side, and lithium ions (Li ⁺ ) are accumulated there. On the other hand, at the time of discharge, the lithium ions (Li ⁺ ) accumulated in the negative electrode are returned to the positive electrode side, and electrons are supplied to the operating portion 6. In the illustrated example, a light bulb is used as a model for the operating portion 6, and the light bulb is turned on by electric discharge.

When an all-solid secondary battery having the layer structure shown in FIG. 1 is placed in a 2032 type coin case, the all-solid secondary battery is referred to as an all-solid secondary battery electrode sheet, and the all-solid secondary battery electrode sheet is referred to as an all-solid secondary battery electrode sheet. Batteries manufactured in a 2032 type coin case are sometimes referred to as all-solid secondary batteries.

(Positive electrode active material layer, solid electrolyte layer, negative electrode active material layer)
In the all-solid-state secondary battery 10, both the positive electrode active material layer and the negative electrode active material layer are composed of the electrode sheet for the all-solid-state secondary battery of the present invention, and contain the composite electrode active material of the present invention. There is. Therefore, the all-solid-state secondary battery 10 exhibits excellent battery performance. The composite electrode active material contained in the positive electrode active material layer 4 and the negative electrode active material layer 2 may be of the same type or different from each other.
In the present invention, either or both of the positive electrode active material layer and the negative electrode active material layer may be simply referred to as an active material layer or an electrode active material layer. Further, either or both of the positive electrode active material and the negative electrode active material may be collectively referred to as an active material or an electrode active material.

In the all-solid-state secondary battery 10, the negative electrode active material layer can be a lithium metal layer. Examples of the lithium metal layer include a layer formed by depositing or molding a lithium metal powder, a lithium foil, a lithium vapor deposition film, and the like. The thickness of the lithium metal layer can be, for example, 1 to 500 μm regardless of the thickness of the negative electrode active material layer.

The positive electrode current collector 5 and the negative electrode current collector 1 are preferably electron conductors.
In the present invention, either or both of the positive electrode current collector and the negative electrode current collector may be collectively referred to as a current collector.
As a material for forming the positive electrode current collector, in addition to aluminum, aluminum alloy, stainless steel, nickel and titanium, the surface of aluminum or stainless steel is treated with carbon, nickel, titanium or silver (a thin film is formed). Of these, aluminum and aluminum alloys are more preferable.
As a material for forming the negative electrode current collector, in addition to aluminum, copper, copper alloy, stainless steel, nickel and titanium, carbon, nickel, titanium or silver is treated on the surface of aluminum, copper, copper alloy or stainless steel. Preferably, aluminum, copper, copper alloy and stainless steel are more preferable.

The shape of the current collector is usually a film sheet, but a net, a punched body, a lath body, a porous body, a foam body, a molded body of a fiber group, or the like can also be used.
The thickness of the current collector is not particularly limited, but is preferably 1 to 500 μm. Further, it is also preferable that the surface of the current collector is made uneven by surface treatment.

In the present invention, a functional layer, a member, or the like is appropriately interposed or arranged between or outside each of the negative electrode current collector, the negative electrode active material layer, the solid electrolyte layer, the positive electrode active material layer, and the positive electrode current collector. You may. Further, each layer may be composed of a single layer or a plurality of layers.

[Manufacturing of all-solid-state secondary batteries]
The all-solid-state secondary battery can be manufactured by a conventional method. Specifically, the all-solid-state secondary battery can be manufactured by forming an active material layer using the electrode composition or the like of the present invention. However, when a base material other than the current collector is used for forming the active material layer, the base material is peeled off from the active material and used for manufacturing an all-solid-state secondary battery. This makes it possible to manufacture an all-solid-state secondary battery that exhibits excellent battery performance and even smaller electrical resistance. The details will be described below.

In the all-solid-state secondary battery of the present invention, the electrode composition of the present invention is appropriately applied onto a base material (for example, a metal foil serving as a current collector) to form a coating film (film formation). It can be manufactured by performing a method including (via) (a method for manufacturing a sheet for an all-solid-state secondary battery of the present invention).
For example, a positive electrode composition is applied onto a metal foil that is a positive electrode current collector to form a positive electrode active material layer, and a positive electrode sheet for an all-solid secondary battery is produced. Next, a solid electrolyte composition for forming the solid electrolyte layer is applied onto the positive electrode active material layer to form the solid electrolyte layer. Further, the composition for the negative electrode is applied on the solid electrolyte layer to form the negative electrode active material layer. By superimposing a negative electrode current collector (metal leaf) on the negative electrode active material layer, an all-solid secondary battery having a structure in which a solid electrolyte layer is sandwiched between the positive electrode active material layer and the negative electrode active material layer can be obtained. Can be done. This can be enclosed in a housing to obtain a desired all-solid-state secondary battery.
Further, by reversing the forming method of each layer, a negative electrode active material layer, a solid electrolyte layer and a positive electrode active material layer are formed on the negative electrode current collector, and the positive electrode current collector is superposed to manufacture an all-solid secondary battery. You can also do it.

As another method, the following method can be mentioned. That is, as described above, a positive electrode sheet for an all-solid-state secondary battery is produced. Further, a negative electrode composition is applied onto a metal foil which is a negative electrode current collector to form a negative electrode active material layer, and a negative electrode sheet for an all-solid secondary battery is produced. Next, a solid electrolyte layer is formed on the active material layer of any one of these sheets as described above. Further, the other of the positive electrode sheet for the all-solid-state secondary battery and the negative electrode sheet for the all-solid-state secondary battery is laminated on the solid electrolyte layer so that the solid electrolyte layer and the active material layer are in contact with each other. In this way, an all-solid-state secondary battery can be manufactured.
As another method, the following method can be mentioned. That is, as described above, a positive electrode sheet for an all-solid-state secondary battery and a negative electrode sheet for an all-solid-state secondary battery are produced. Separately from this, the solid electrolyte composition is applied onto the base material to prepare a solid electrolyte sheet for an all-solid secondary battery composed of a solid electrolyte layer. Further, the positive electrode sheet for the all-solid-state secondary battery and the negative electrode sheet for the all-solid-state secondary battery are laminated so as to sandwich the solid electrolyte layer peeled from the base material. In this way, an all-solid-state secondary battery can be manufactured.

In the above-mentioned production method, the electrode composition of the present invention may be used for any one of the positive electrode composition and the negative electrode composition, and it is preferable to use the electrode composition of the present invention in both cases.

<Formation of each layer (deposition)>
The application method of each composition is not particularly limited and can be appropriately selected. For example, coating (preferably wet coating), spray coating, spin coating coating, dip coating, slit coating, stripe coating, bar coating coating can be mentioned.
At this time, each composition may be subjected to a drying treatment after being applied, or may be subjected to a drying treatment after being applied in multiple layers. The drying temperature is not particularly limited. The lower limit is preferably 30 ° C. or higher, more preferably 60 ° C. or higher, and even more preferably 80 ° C. or higher. The upper limit is preferably 300 ° C. or lower, more preferably 250 ° C. or lower, and even more preferably 200 ° C. or lower. By heating in such a temperature range, the dispersion medium can be removed and a solid state (coating dry layer) can be obtained. Further, it is preferable because the temperature is not raised too high and each member of the all-solid-state secondary battery is not damaged. As a result, in an all-solid-state secondary battery, it is possible to obtain excellent overall performance, good binding properties, and good ionic conductivity even without pressurization.

It is preferable to pressurize each layer or the all-solid-state secondary battery after preparing the coated electrode composition or the all-solid-state secondary battery. It is also preferable to pressurize the layers in a laminated state. Examples of the pressurizing method include a hydraulic cylinder press machine and the like. The pressing force is not particularly limited, and is generally preferably in the range of 5 to 1500 MPa.
Further, the applied electrode composition may be heated at the same time as pressurization. The heating temperature is not particularly limited, and is generally in the range of 30 to 300 ° C. It can also be pressed at a temperature higher than the glass transition temperature of the inorganic solid electrolyte.
The pressurization may be carried out in a state where the coating solvent or the dispersion medium has been dried in advance, or may be carried out in a state where the solvent or the dispersion medium remains.
In addition, each composition may be applied at the same time, and the application drying press may be performed simultaneously and / or sequentially. After applying to separate substrates, they may be laminated by transfer.

The atmosphere during pressurization is not particularly limited, and may be any of air, dry air (dew point −20 ° C. or lower), inert gas (for example, argon gas, helium gas, nitrogen gas) and the like.
The pressing time may be short (for example, within several hours) and high pressure may be applied, or medium pressure may be applied for a long time (1 day or more). In the case of an all-solid-state secondary battery other than the all-solid-state secondary battery sheet, for example, in the case of an all-solid-state secondary battery, an all-solid-state secondary battery restraint (screw tightening pressure, etc.) can be used in order to continue applying a medium pressure.
The press pressure may be uniform or different with respect to the pressed portion such as the sheet surface.
The press pressure can be changed according to the area or film thickness of the pressed portion. It is also possible to change the same part step by step with different pressures.
The pressed surface may be smooth or roughened.

<Initialization>
The all-solid-state secondary battery manufactured as described above is preferably initialized after manufacturing or before use. The initialization is not particularly limited, and can be performed, for example, by performing initial charging / discharging with the press pressure increased, and then releasing the pressure until the pressure reaches the general working pressure of the all-solid-state secondary battery.

[Applications for all-solid-state secondary batteries]
The all-solid-state secondary battery of the present invention can be applied to various applications. The application mode is not particularly limited, but for example, when mounted on an electronic device, a laptop computer, a pen input computer, a mobile computer, an electronic book player, a mobile phone, a cordless phone handset, a pager, a handy terminal, a mobile fax, or a mobile phone. Examples include copying, mobile printers, headphone stereos, video movies, LCD TVs, handy cleaners, portable CDs, mini discs, electric shavers, transceivers, electronic notebooks, calculators, memory cards, portable tape recorders, radios, backup power supplies, etc. Other consumer products include automobiles, electric vehicles, motors, lighting equipment, toys, game equipment, road conditioners, watches, strobes, cameras, medical equipment (pacemakers, hearing aids, shoulder massagers, etc.). Furthermore, it can be used for various munitions and space. It can also be combined with a solar cell.

The present invention will be described in more detail below based on examples, but the present invention is not construed as being limited thereto. In the following examples, "parts" and "%" representing the composition are based on mass unless otherwise specified. In the present invention, "room temperature" means 25 ° C.

<Sulfide-based inorganic solid electrolyte synthesis>
As a sulfide-based inorganic solid electrolyte, T.I. Ohtomo, A. Hayashi, M. et al. Tassumisago, Y. et al. Tsuchida, S.A. Hama, K.K. Kawamoto, Journal of Power Sources, 233, (2013), pp231-235 and A. et al. Hayashi, S.A. Hama, H.M. Morimoto, M.D. Tassumisago, T. et al. Minami, Chem. Lett. , (2001), pp872-873, Li-PS-based glass was synthesized with reference to non-patent documents.
Specifically, in a glove box under an argon atmosphere (dew point -70 ° C.), lithium sulfide _(Li 2 S, Aldrich Corp., purity> 99.98%) 2.42 g, diphosphorus pentasulfide _(P 2 S _5. Aldrich, purity> 99%) 3.90 g was weighed and put into a mortar. The molar ratios of Li ₂ S and P ₂ S ₅ were Li ₂ S: P ₂ S ₅ = 75: 25. On the agate mortar, the mixture was mixed for 5 minutes using an agate pestle.
66 g of zirconia beads having a diameter of 5 mm was put into a 45 mL container made of zirconia (manufactured by Fritsch), the whole amount of the above mixture was put into the container, and the container was sealed under an argon atmosphere. A container is set on a planetary ball mill P-7 (trade name) manufactured by Fritsch, and mechanical milling is performed at 25 ° C. at a rotation speed of 510 rpm for 20 hours to produce a yellow powder sulfide-based inorganic solid electrolyte (Li-PS). System glass, LPS) 6.20 g was obtained. The average particle size was 2.6 μm.

<Synthesis of binder A>
In a 2L three-necked flask equipped with a reflux condenser and a gas introduction cock, 7.2 g of a 40% by mass heptane solution of macromonomer M-1 prepared as described below, methyl acrylate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) Add 12.4 g, acrylic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) 6.7 g, heptane (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) 207 g, and azoisobutyronitrile 1.4 g to a flow rate of 200 mL / min. After introducing nitrogen gas for 10 minutes, the temperature was raised to 100 ° C. Liquid prepared in a separate container (40 mass% heptane solution of macromonomer M-1 93.1 g, methyl acrylate 222.8 g, acrylic acid 120.0 g, heptane 300.0 g, azoisobutyronitrile 2.1 g The mixed solution) was added dropwise over 4 hours. After the dropping was completed, 0.5 g of azoisobutyronitrile was added. Then, after stirring at 100 ° C. for 2 hours, the mixture was cooled to room temperature and filtered to obtain a dispersion of binder A. The solid component concentration was 39.2%. The average particle size was 150 nm.

A 40 mass% heptane solution of macromonomer M-1 was prepared as follows.
A self-condensate of 12-hydroxystearic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) (GPC polystyrene standard number average molecular weight: 2,000) is reacted with glycidyl methacrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) and methacrylic as a macromonomer. Macro by reacting acrylic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) with a polymer polymerized at a ratio of 1: 0.99: 0.01 (molar ratio) with methyl acid and glycidyl methacrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) Monomer M-1 was obtained. The SP value of this macromonomer M-1 was 9.3, and the number average molecular weight was 11000.

<Synthesis of composite electrode active material>
(Ball mill method)
In the following manner, the following step (1) is performed using the coating material 1 described in Table 1 below, and then the following step (2) is performed twice using the

coating materials

2 and 3 described in Table 1 below. The composite electrode active material No. 1 shown in Table 1 below. 7 was synthesized.
-Process (1)-
66 g of zirconia beads having a diameter of 5 mm were put into a 45 mL container made of zirconia (manufactured by Fritsch), and 3 g of LPS, 0.2 g of acetylene black as a conductive auxiliary agent, and 10 g of NMC having an average particle size of 5 μm as an active material were put into a ball mill. The active material 1 having a coating layer containing LPS and a conductive auxiliary agent was obtained by stirring at 370 rpm for 30 minutes at room temperature (trade name: P-7, manufactured by Fritsch) (number of coatings 1).
-Process (2)-
The active material 1, 0.05 g of LPS, and 0.4 g of acetylene black are stirred in a ball mill (trade name: P-7, manufactured by Fritsch) at room temperature for 30 minutes at 370 rpm, and the LPS and the conductive additive are stirred. An active material 2 having a coating layer containing the above was obtained (number of coatings 2).
The active material 2, 0.1 g of LPS, and 0.4 g of acetylene black are stirred in a ball mill (trade name: P-7, manufactured by Fritsch) at room temperature for 30 minutes at 370 rpm, and the LPS and the conductive additive are stirred. Composite electrode active material No. 1 having a coating layer containing 7 was obtained (number of coatings 3).

Composite electrode active material No. In the synthesis of No. 7, the composite electrode active material No. 1 was used, except that the composition and the number of coatings shown in Table 1 below were adopted. In the same manner as in No. 7, the composite electrode active material No. 1 shown in Table 1 below. Composite electrode active materials other than 7 and 12 were synthesized.

(High-speed airflow impact method)
The following step (1a) is performed using the coating material 1 described in Table 1 below, and then the following step (2a) is performed using the coating material 3 described in Table 1 below. No. 1 of the composite electrode active material according to 1. 12 was synthesized.
-Step (1a)-
66 g of zirconia beads having a diameter of 5 mm were put into a 45 mL container made of zirconia (manufactured by Fritsch), and 3 g of LPS, 0.2 g of acetylene black as a conductive auxiliary agent, and 10 g of NMC having an average particle size of 5 μm as an active material were put into a ball mill. A composite containing LPS and a conductive auxiliary agent was obtained by stirring with (trade name: P-7, manufactured by Fritsch) at room temperature at 150 rpm for 30 minutes. Then, using a high-speed airflow impact device (NHS-0 (trade name) manufactured by Nara Machinery Co., Ltd.), a coating layer containing LPS and a conductive additive was obtained by undergoing a dry compounding process at 12000 rpm for 5 minutes. The active material 1 to have was obtained (number of coatings 1).
-Step (2a)-
The active material 1, LPS 0.1 g, and acetylene black 0.4 g are stirred in a ball mill (trade name: P-7, manufactured by Fritsch) at room temperature for 30 minutes at 150 rpm, and the LPS and the conductive additive are stirred. A complex containing the above was obtained. After that, using a high-speed airflow impact device (NHS-0 (trade name) manufactured by Nara Machinery Co., Ltd.), a dry compounding process of 12000 rpm for 5 minutes was performed (number of coatings 2), LPS and conductive auxiliary agent. Composite electrode active material No. 1 having a coating layer containing I got twelve.

<Manufacturing of all-solid-state secondary battery>
As shown below, the all-solid-state secondary battery No. 1 having the layer structure shown in FIG. 1-7 was prepared.

(Preparation of Composition 1 for Positive Electrode)
66 g of zirconia beads having a diameter of 5 mm were put into a 45 mL container made of zirconia (manufactured by Fritsch), and the composite electrode active material No. 1 synthesized above was added. 77.0 g, LPS 0.9 g, and heptane 12.3 g as a dispersion medium were added. A container was set on the planetary ball mill P-7, and mixing was continued for 10 minutes at a temperature of 25 ° C. and a rotation speed of 100 rpm to prepare a positive electrode composition 1.

(Preparation of composition 1 for negative electrode)
66 g of zirconia beads having a diameter of 5 mm was put into a 45 mL container made of zirconia (manufactured by Fritsch), 2.8 g of LPS synthesized above, and 12.3 g of heptane as a dispersion medium were put. The container was set on a planetary ball mill P-7 manufactured by Fritsch, and mixed at a temperature of 25 ° C. and a rotation speed of 300 rpm for 2 hours. After that, 7.0 g of CGB20 (trade name, manufactured by Nippon Graphite Co., Ltd.) was put into a container as an active material, and similarly, the container was set on a planetary ball mill P-7 and mixed at a temperature of 25 ° C. and a rotation speed of 200 rpm for 15 minutes. Subsequently, the composition 1 for the negative electrode was prepared.

(Preparation of positive electrode sheet)
The positive electrode composition 1 prepared above is placed on an aluminum foil (positive electrode current collector) with an applicator (trade name: SA-201 Baker type applicator, manufactured by Tester Sangyo Co., Ltd.) with a basis weight of 30 mg / cm ^2. After heating at 80 ° C. for 1 hour, the mixture was further dried at 110 ° C. for 1 hour. Then, using a heat press machine, pressure was applied while heating (120 ° C.) (20 MPa, 1 minute) to prepare a positive electrode sheet having a positive electrode active material layer on the positive electrode current collector.

(Preparation of negative electrode sheet)
The negative electrode composition 1 prepared above is placed on a stainless steel (SUS) foil (negative electrode current collector) with an applicator (trade name: SA-201 Baker type applicator, manufactured by Tester Sangyo Co., Ltd.) at 15 mg / cm ² The mixture was applied so as to have a basis weight of, heated at 80 ° C. for 1 hour, and then dried at 110 ° C. for 1 hour. Then, using a heat press machine, pressure was applied while heating (120 ° C.) (20 MPa, 1 minute) to prepare a negative electrode sheet having a negative electrode active material layer on the negative electrode current collector.

Using the prepared positive electrode sheet and negative electrode sheet, an all-solid-state secondary battery was prepared as follows.
The positive electrode sheet was punched into a disk shape having a diameter of 10 mmφ and placed in a cylinder made of polyethylene terephthalate (PET) having a diameter of 10 mmφ. 30 mg of the synthesized LPS was placed on the surface of the positive electrode active material layer in the cylinder, and a rod made of SUS having a diameter of 10 mm was inserted through the openings at both ends of the cylinder. The positive electrode current collector side of the positive electrode sheet and the LPS were pressure-formed with a SUS rod at a pressure of 350 MPa to form a solid electrolyte layer. Then, the SUS rod arranged on the solid electrolyte layer side was once removed, and a disc-shaped negative electrode sheet having a diameter of 10 mmφ was inserted onto the solid electrolyte layer in the cylinder. The removed SUS rod was reinserted into the cylinder and fixed under a pressure of 50 MPa. In this way, aluminum foil (thickness 20 μm) -positive electrode active material layer (thickness 100 μm) -sulfide-based inorganic solid electrolyte layer (thickness 200 μm) -negative electrode active material layer (thickness 30 μm) -SUS foil (thickness) An all-solid-state secondary battery having a composition of 20 μm) was obtained.

All-solid-state secondary battery No. In the preparation of 1-7, the composite electrode active material No. Instead of No. 7, the composite electrode active material No. All-solid-state secondary batteries No. 1 to 6 and 8 to 24 were used. In the same manner as in 1-7, the all-solid-state secondary battery No. 1-1 to 1-6 and 1 to 8 to 1-24 were prepared.

All-solid-state secondary battery No. In the production of 1-7, the all-solid-state secondary battery No. 1 except that the following positive electrode composition 2 and negative electrode composition 2 were used instead of the positive electrode composition 1 and the negative electrode composition 1. In the same manner as in 1-7, the all-solid-state secondary battery No. 1-26 was made.

(Preparation of composition 2 for positive electrode)
66 g of zirconia beads having a diameter of 5 mm was put into a 45 mL container made of zirconia (manufactured by Fritsch), 2.8 g of LPS synthesized above, and 12.3 g of heptane as a dispersion medium were put. The container was set on a planetary ball mill P-7 manufactured by Fritsch, and mixed at a temperature of 25 ° C. and a rotation speed of 300 rpm for 2 hours. Then, 7.0 g of NMC as an active material was put into a container, and similarly, the container was set in a planetary ball mill P-7 and mixed at a temperature of 25 ° C. and a rotation speed of 200 rpm for 15 minutes to prepare a positive electrode composition 2. ..

(Preparation of composition 2 for negative electrode)
66 g of zirconia beads having a diameter of 5 mm were put into a 45 mL container made of zirconia (manufactured by Fritsch), and the composite electrode active material No. 1 synthesized above was added. 26 7.0 g, LPS 0.9 g, and heptane 12.3 g as a dispersion medium were added. The container was set on the planetary ball mill P-7, and mixing was continued for 10 minutes at a temperature of 25 ° C. and a rotation speed of 100 rpm to prepare a negative electrode composition 2.

All-solid-state secondary battery No. In the preparation of 1-26, the composite electrode active material No. Instead of 26, the composite electrode active material No. All-solid-state secondary battery No. 1-25 and 1-27-30 were used. In the same manner as in 1-7, the all-solid-state secondary battery No. 1-25 and 1-27-30 were made.

<Ratio of carbon atoms to lithium atoms C / Li>
The C / Li in each region of the coating layer of the synthesized composite electrode active material was measured as follows.
The composite electrode active material powder is pressed at 350 MPa to obtain composite electrode active material powder pellets, and the pellets are cut and used with an ion milling device (Hitachi Seisakusho, IM4000PLUS (trade name)) to accelerate voltage 3 kV and discharge voltage 1.5 V. It was cut out under the conditions of a treatment time of 4 hours and an argon gas flow rate of 0.1 ml / min. The cross section of the composite electrode active material was observed by SEM (Hitachi, MINISCOPE TM3030PLUS (trade name)) at a magnification of 5,000 times. For the measured values in each region, 10 composite electrode active materials were randomly selected, and for each composite electrode active material, the circumferential direction was at four locations with a central angle of 90 °, and the thickness direction of the composite electrode active material was The C / Li at one location was calculated near the center of each region, and the arithmetic mean value of the values of each region obtained from the 10 composite electrode active materials was adopted.
The active material contact surface is composed of SEM-EDX (Hitachi, Ltd., QUANTAX70 (trade name)) (Mn or Al derived from the positive electrode active material, Li derived from the inorganic solid electrolyte in the coating layer, or Si derived from the negative electrode active material. The portion where Sn and Li) derived from the inorganic solid electrolyte in the coating layer change discontinuously was defined as the contact surface between the active material and the coating layer. The surface of the coating layer was defined as a portion where the composition (Li and voids derived from the inorganic solid electrolyte in the coating layer) changed discontinuously with SEM-EDX. The area A, the area C, and the area B were measured on the same straight line (on one radius).

In the all-solid-state secondary battery, the composite electrode active material maintained C / Li in each region of the coating layer. For C / Li in each region of the coating layer of the composite electrode active material in the all-solid-state secondary battery, the composite electrode active material was taken out by disassembling the all-solid-state secondary battery, and the taken-out composite electrode active material was used. And measured in the same manner as above.

The coverage of the coating layer on the active material of the composite electrode active material synthesized above was calculated as follows.
Ten composite electrode active materials were randomly selected, and for each composite electrode active material, the circumference X of the active material contact portion and the length s of the uncoated portion region were measured, and the composite electrode active material was coated from the following formula. The rate was calculated and the arithmetic mean value of the values obtained from the 10 composite electrode active materials was adopted.
Coverage (%) = 100 x (X-s) / X

In the all-solid-state secondary battery, the composite electrode active material maintained the coverage of the coating layer with respect to the active material of the composite electrode active material. The coverage of the coating layer on the active material of the composite electrode active material in the all-solid-state secondary battery is determined by disassembling the all-solid-state secondary battery, taking out the composite electrode active material, and using the taken-out composite electrode active material. The measurement was performed in the same manner as above.

For the layer thickness of the coating layer of the synthesized composite electrode active material, 10 composite electrode active materials were randomly selected, and for each composite electrode active material, 40 active material contact portions and the coating portion surface were randomly selected. The shortest distance to and from was measured from an image with a magnification of × 5000 times by cutting out a cross section in the same manner as above and using an SEM (Hitachi Seisakusho, MINISCOPE TM3030PLUS (trade name)), and the arithmetic mean value was adopted.

In the all-solid-state secondary battery, the composite electrode active material maintained the layer thickness of the coating layer of the composite electrode active material. For the layer thickness in each region of the coating layer of the composite electrode active material in the all-solid-state secondary battery, the composite electrode active material was taken out by disassembling the all-solid-state secondary battery, and the taken-out composite electrode active material was used. The measurement was performed in the same manner as above.

<Evaluation of battery characteristics (high rate characteristic test)>
Using the all-solid-state secondary battery produced above, charging / discharging of 4.3 V to 3.0 V was performed once under the conditions of a charging current value of 0.13 mA and a discharge current value of 0.13 mA in an environment of 30 ° C. ( Initialized).
Then, as a high-rate characteristic test, charging / discharging was performed at 4.3 V to 3.0 V under the condition of a charge / discharge current value of 3.9 mA in an environment of 25 ° C.
The discharge capacity (1) at the time of initialization discharge and the discharge capacity (2) at the time of discharge of 4.3V to 3.0V are measured, and the discharge capacity retention rate is measured by the following formula, and this discharge capacity is measured. The high rate characteristics were evaluated by applying the maintenance rate to the following evaluation criteria. "E" or higher is the pass of this test.

Discharge capacity retention rate (%) = (Discharge capacity (2) / Discharge capacity (1)) x 100

-Evaluation criteria-
AA: 70% or more and less than 80% A: 60% or more and less than 70% B: 50% or more and less than 60% C: 40% or more and less than 50% D: 30% or more and less than 40% E: 20% or more and less than 30% F: 15% or more and less than 20% G: 0% or more and less than 15%

<Note to table>
No. 1 to 30: No. 1 of the composite electrode active material. Is shown.
No. 1-1 to 1-30: No. 1 of the all-solid-state secondary battery. Is shown.
SE: Inorganic solid electrolyte NMC: LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (lithium nickel manganese cobalt oxide), manufactured by Toshima Manufacturing Co., Ltd., average particle size 5.0 μm
NCA: LiNi _0.85 Co _0.10 Al _0.05 O ₂ (lithium nickel cobalt aluminate), manufactured by Nihon Kagaku Sangyo Co., Ltd., average particle size 6.0 μm
Si: Alfa Aesar, average particle size 3.0 μm
Sn: Made by Alfa Aesar, average particle size 3.5 μm
LLZ: Li ₇ La ₃ Zr ₂ O ₁₂ , manufactured by Toshima Manufacturing Co., Ltd., average particle size 1.3 μm
AB: Acetylene Black, manufactured by Denka, average particle size 40 nm, aspect ratio 1.0
VGCF: Vapor-grown carbon fiber, manufactured by Showa Denko, average particle size 1.2 μm, aspect ratio 11
CNT: Carbon nanotube, manufactured by Alfa Aesar, average particle size 1 μm, aspect ratio 100
Li-435: Product name, Denka acetylene black, average particle size 23 nm, aspect ratio 1.2
HSBR: Hydrogenated styrene-butadiene rubber

As is clear from Table 1, all the all-solid-state secondary batteries using the composite electrode active material that do not meet the provisions of the present invention failed the high-rate characteristic test.
On the other hand, all the all-solid-state secondary batteries using the composite electrode active material of the present invention passed the high-rate characteristic test. Further, for example, the all-solid-state secondary battery No. From the result of No. 11, it can be seen that the battery performance is further improved when the conductive auxiliary agent present in the region B contains fibrous carbon.

Although the present invention has been described with its embodiments, we do not intend to limit our invention in any detail of the description unless otherwise specified, and contrary to the spirit and scope of the invention set forth in the appended claims. I think that it should be widely interpreted without.

The present application claims priority based on Japanese Patent Application No. 2019-667059 filed in Japan on March 29, 2019, which is referred to herein and is described herein. Import as a part.

1 Negative electrode current collector 2 Negative electrode active material layer 3 Solid electrolyte layer 4 Positive electrode active material layer 5 Positive electrode current collector 6 Operating part 10 All-solid-state secondary battery

Claims

A composite electrode active material having an active material and a coating layer covering the active material.
The coating layer contains an inorganic solid electrolyte and a conductive auxiliary agent,
A composite electrode active material in which lithium atoms and carbon atoms contained in the coating layer satisfy the relationship defined by the following formula (I) with respect to the number of atoms.
A1 <B1 formula (I)
In the formula, A1 represents the ratio C / Li of the number of carbon atoms to the number of lithium atoms in the region A having a thickness of 0.5 μm outward from the active material contact portion of the coating layer, and B1 is the surface of the coating layer. The ratio C / Li of the number of carbon atoms to the number of lithium atoms in the region B having a thickness of 0.5 μm is shown from the inside to the inside. However, B1 is 99/1 or less.
The composite electrode according to claim 1, wherein the lithium atom and the carbon atom contained in the region C between the regions A and B satisfy the relationship defined by the following formula (IIA) or formula (IIB) with respect to the number of atoms. Active material.
A1 ≤ C1 <B1 equation (IIA)
A1 <C1 ≤ B1 equation (IIB)
In the formula, A1 and B1 are synonymous with A1 and B1 in the formula (I). C1 indicates the ratio C / Li of the number of carbon atoms to the number of lithium atoms in the region C.
The composite electrode active material according to claim 1 or 2, wherein the conductive auxiliary agent contains fibrous carbon.
The composite electrode active material according to any one of claims 1 to 3, wherein the conductive auxiliary agent present in the region B contains fibrous carbon.
The composite electrode active material according to any one of claims 1 to 4, wherein B1 is 50/50 to 99/1.
A composition for an electrode containing the composite electrode active material according to any one of claims 1 to 5 and a dispersion medium.
The electrode composition according to claim 6, which comprises a binder.
The electrode composition according to claim 7, wherein the binder is in the form of particles.
An electrode sheet for an all-solid-state secondary battery containing the composite electrode active material according to any one of claims 1 to 5.
The electrode sheet for an all-solid-state secondary battery according to claim 9, which includes a binder.
The electrode sheet for an all-solid-state secondary battery according to claim 10, wherein the binder is in the form of particles.
An all-solid-state secondary battery including a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer in this order.
An all-solid-state secondary battery in which at least one layer of the positive electrode active material layer and the negative electrode active material layer is a layer composed of the electrode sheet for an all-solid-state secondary battery according to any one of claims 9 to 11. ..
The method for producing a composite electrode active material according to any one of claims 1 to 5.
It has the following step (1) and the following step (2) to be performed once or multiple times, and the mixing ratio of the inorganic solid electrolyte and the conductive auxiliary agent in the following step (1) and the final step (2) is changed. A method for producing a composite electrode active material, wherein a coating layer satisfying the relationship defined by the formula (I) is formed on the surface of the active material.
Step (1): Mixing the active material, the inorganic solid electrolyte and the conductive auxiliary agent Step (2): Mixing the mixture obtained in the above step (1) with the inorganic solid electrolyte and the conductive auxiliary agent.
A method for producing an electrode sheet for an all-solid-state secondary battery, which comprises forming a film of the electrode composition according to any one of claims 6 to 8.
A method for manufacturing an all-solid-state secondary battery, which manufactures an all-solid-state secondary battery through the manufacturing method according to claim 14.