WO2025115661A1 - Composite, method for producing composite, positive electrode mixed material, positive electrode for lithium ion battery, lithium ion battery, activated carbon for solid-state lithium ion battery, use of activated carbon, and method for producing solid-state lithium ion battery - Google Patents

Abstract

This composite comprises activated carbon and at least one of elemental sulfur or discharge product of elemental sulfur. The activated carbon has a peak area percentage of oxygen functional groups of 15% or less in the C1s spectrum as obtained by X-ray photoelectron spectroscopy.

Description

Composite, method for manufacturing the composite, positive electrode mixture, positive electrode for lithium ion battery, lithium ion battery, activated carbon for all-solid-state lithium ion battery, use of activated carbon, and method for manufacturing all-solid-state lithium ion battery

The present invention relates to a composite, a method for producing the composite, a positive electrode mixture, a positive electrode for a lithium ion battery, a lithium ion battery, an activated carbon for an all-solid-state lithium ion battery, use of the activated carbon, and a method for producing an all-solid-state lithium ion battery.
Specifically, the present invention relates to a composite capable of improving rate characteristics, a method for producing the composite, a positive electrode mixture, a positive electrode for a lithium ion battery, a lithium ion battery, activated carbon for an all-solid-state lithium ion battery, use of the activated carbon, and a method for producing an all-solid-state lithium ion battery.

It has been proposed to use a sulfur-activated carbon composite for the positive electrode of an all-solid-state lithium-ion battery.
On the other hand, it has been reported that in liquid-type lithium-ion batteries, the characteristics can be improved by increasing the oxygen functional group of the activated carbon used in the sulfur-activated carbon composite (Non-Patent Document 1).

Performance Enhancement of Rechargeable Sulfur Cathode Utilizing Microporous Activated Carbon Composite, Electrochemistry, 2017, 85(10), pp. 671-674

The present inventors attempted to further improve the rate characteristics of an all-solid-state lithium ion battery using a sulfur-activated carbon composite (hereinafter also simply referred to as a "composite") in the positive electrode from the viewpoint of the activated carbon used.
Conventional techniques including that described in Non-Patent Document 1 have not been able to solve such problems.

One of the objects of the present invention is to provide a composite that can improve rate characteristics, particularly when used in the positive electrode of an all-solid-state lithium-ion battery, a method for manufacturing the composite, a positive electrode mixture, a positive electrode for a lithium-ion battery, a lithium-ion battery, activated carbon for an all-solid-state lithium-ion battery, use of activated carbon, and a method for manufacturing an all-solid-state lithium-ion battery.

As a result of extensive investigations, the present inventors have found that when activated carbon having a reduced amount of oxygen functional groups is used as the activated carbon for use in the sulfur-activated carbon composite, the rate characteristics of an all-solid-state lithium ion battery or the like can be improved, and have completed the present invention.
According to the present invention, the following composites and the like can be provided.
1. Activated carbon having a peak area ratio of oxygen functional groups in a C1s spectrum obtained by X-ray photoelectron spectroscopy of 15% or less;
A composite material comprising: at least one of elemental sulfur and a discharge product of elemental sulfur.
2. The composite according to 1, wherein the activated carbon has a specific surface area of 2300 m ² /g or more.
3. The composite according to 1 or 2, wherein the activated carbon has a total pore volume of 1.2 cc/g or more.
4. The composite according to any one of 1 to 3, wherein the activated carbon has a micropore volume of 1.2 cc/g or more.
5. Activated carbon having a peak area ratio of oxygen functional groups in a C1s spectrum obtained by X-ray photoelectron spectroscopy of 15% or less;
A method for producing a composite comprising: combining elemental sulfur and at least one of a discharge product of elemental sulfur.
6. The method for producing a composite according to 5, wherein the activated carbon has a specific surface area of 2300 m ² /g or more.
7. The method for producing a composite according to 5 or 6, wherein the activated carbon has a total pore volume of 1.2 cc/g or more.
8. The method for producing a composite according to any one of 5 to 7, wherein the activated carbon has a micropore volume of 1.2 cc/g or more.
9. The method for producing a composite according to any one of 5 to 8, wherein the activated carbon has been subjected to a treatment for reducing oxygen functional groups at a temperature of 500° C. or higher and 1000° C. or lower.
10. A composite according to any one of 1 to 4, or a composite produced by the method for producing a composite according to any one of 5 to 9,
A positive electrode composite comprising: a sulfide solid electrolyte;
11. The positive electrode mixture according to claim 10, wherein the sulfide solid electrolyte contains at least a lithium atom, a phosphorus atom, a sulfur atom, and a halogen atom.
12. A positive electrode for a lithium ion battery comprising the positive electrode mixture according to 10 or 11.
13. A lithium ion battery comprising the positive electrode mixture according to 10 or 11.
14. Activated carbon for all-solid-state lithium-ion batteries, having a peak area ratio of oxygen functional groups in a C1s spectrum obtained by X-ray photoelectron spectroscopy of 15% or less.
15. Use of activated carbon, in which the peak area ratio of oxygen functional groups in a C1s spectrum obtained by X-ray photoelectron spectroscopy is 15% or less, for an all-solid-state lithium ion battery.
16. A method for producing an all-solid-state lithium ion battery, comprising treating activated carbon at a temperature of 500° C. or more and 1000° C. or less to reduce oxygen functional groups.

The present invention provides a composite that can improve rate characteristics, particularly when used in the positive electrode of an all-solid-state lithium-ion battery, a method for manufacturing the composite, a positive electrode mixture, a positive electrode for a lithium-ion battery, a lithium-ion battery, activated carbon for an all-solid-state lithium-ion battery, use of activated carbon, and a method for manufacturing an all-solid-state lithium-ion battery.

The composite of the present invention, the method for producing the composite, the positive electrode mixture, the positive electrode for a lithium ion battery, the lithium ion battery, the activated carbon for an all-solid-state lithium ion battery, the use of the activated carbon, and the method for producing an all-solid-state lithium ion battery will be described in detail below.
In this specification, "x to y" represents a numerical range of "not less than x and not more than y." The upper and lower limits described in relation to the numerical ranges can be combined in any combination.
In addition, among the individual embodiments of the aspects of the present invention described below, it is possible to combine two or more embodiments that are not mutually contradictory, and an embodiment combining two or more embodiments is also an embodiment of the aspects of the present invention.

1. Composite The composite according to one embodiment of the present invention comprises an activated carbon having an oxygen functional group peak area ratio (hereinafter, also simply referred to as "peak area ratio") of 15% or less in a C1s spectrum obtained by X-ray photoelectron spectroscopy;
and at least one of elemental sulfur and a discharge product of elemental sulfur.
The composite according to this embodiment can improve the rate characteristics, particularly when used in the positive electrode of an all-solid-state lithium ion battery.
In the composite according to this embodiment, the activated carbon has a peak area ratio of 15% or less, that is, the amount of oxygen functional groups is small.
As described above, it has been reported that in liquid-type lithium-ion batteries, the performance improves as the amount of oxygen functional groups in the activated carbon used in the sulfur-activated carbon composite increases. However, it was unexpectedly found that in an all-solid-state system, the rate performance improves as the amount of oxygen functional groups decreases.
The reason why such an effect is exhibited is not entirely clear, but it is presumed that the small amount of oxygen functional groups suppresses deterioration of the properties of the sulfide solid electrolyte and improves the electronic conductivity of the activated carbon.

(activated carbon)
In one embodiment, the activated carbon has a peak area ratio of 15.0% or less, 14.8% or less, 14.6% or less, 14.4% or less, 14.2% or less, 14.0% or less, 13.8% or less, 13.6% or less, 13.4% or less, 13.2% or less, 13.0% or less, 12.8% or less, or 12.6% or less. The lower limit is not particularly limited, and is, for example, 1.0% or more, 2.0% or more, or 3.0% or more.
The peak area ratio is a value measured by the method described in the Examples.

In one embodiment, the specific surface area of the activated carbon is 1500 m ² /g or more, 1600 ^{m 2} /g or more, 1700 ^{m 2} /g or more, 1800 ^{m 2} /g or more, 1900 ^{m 2} /g or more, 2000 ^{m 2} /g or more, 2100 ^{m 2} /g or more, 2200 ^{m 2} /g or more, or 2300 m ² /g or more. The upper limit is not particularly limited, and is, for example, 4000 ^{m 2} /g or less, 3000 ^{m 2} /g or less, or 2800 m ² /g or less.
In one embodiment, the specific surface area of the activated carbon is 2300 ^{m 2} /g or more, whereby the effect of improving the rate characteristics is more significantly exhibited.
The specific surface area is a value measured by the method described in the Examples.

In one embodiment, the activated carbon is an activated carbon that has been treated at a temperature of 500° C. to 1000° C. to reduce oxygen functionality.
The "treatment for reducing oxygen functional groups" will be described in detail later.

In one embodiment, the activated carbon is pressurized physically activated activated carbon.
The "pressurized physically activated carbon" will be described in detail later.

In one embodiment, the total pore volume of the activated carbon is preferably 1.2 cc/g or more, 1.3 cc/g or more, 1.4 cc/g or more, 1.5 cc/g or more, 1.6 cc/g or more, and 1.7 cc/g or more in that order. The upper limit of the total pore volume is not particularly limited, and may be, for example, 5 cc/g or less, 4 cc/g or less, or 3 cc/g or less.
The total pore volume of physically activated carbon such as general steam activated carbon is less than 1.2 cc/g, which is limited in terms of storing sufficient sulfur in the activated carbon. In contrast, activated carbon having a total pore volume of 1.2 cc/g or more is preferable because it can store more sulfur in the activated carbon.

In one embodiment, the micropore volume of the activated carbon is preferably 1.2 cc/g or more, 1.3 cc/g or more, 1.4 cc/g or more, 1.5 cc/g or more, 1.6 cc/g or more, and 1.7 cc/g or more in that order. The upper limit of the micropore volume is not particularly limited, and may be, for example, 5 cc/g or less, 4 cc/g or less, or 3 cc/g or less.
The micropore volume of physically activated carbon such as general steam activated carbon is less than 1.2 cc/g, which is limited in terms of storing sufficient sulfur in the activated carbon. In contrast, activated carbon having a micropore volume of 1.2 cc/g or more is preferable because it can store more sulfur in the activated carbon.

(Elemental sulfur and discharge products of elemental sulfur)
Although there are no particular limitations on the elemental sulfur (sulfur), the purity is preferably 95% by mass or more, more preferably 96% by mass or more, and particularly preferably 97% by mass or more.
Examples of the crystal system of elemental sulfur include α-sulfur (orthorhombic system), β-sulfur (monoclinic system), γ-sulfur (monoclinic system), and amorphous sulfur. These may be used alone or in combination of two or more. Elemental sulfur becomes a molten liquid when heated.

During the battery reaction, part or all of the elemental sulfur is converted into a discharge product. Therefore, in one embodiment, a discharge product of elemental sulfur is present in the composite. When a discharge product is present, the amount of sulfur contained in the composite is the total amount of elemental sulfur and sulfur contained in the discharge product.
Examples of discharge products of elemental sulfur include Li ₂ S in a fully discharged state and lithium polysulfides in the intermediate stages thereof, such as Li ₂ S ₂ , Li ₂ S ₄ , Li ₂ S ₆ , and Li ₂ S ₈ .

In one embodiment, in the composite, part or all of the elemental sulfur is attached (impregnated) in the pores of the activated carbon. In addition, the elemental sulfur that is not impregnated in the pores is present so as to cover part or all of the activated carbon. Whether or not sulfur is impregnated in the pores of the activated carbon can be confirmed by analyzing the cross section of the activated carbon particles using an analytical method capable of elemental mapping, such as SEM-EDS or TEM-EDX, and evaluating the overlap of elements derived from the activated carbon and sulfur elements.
In one embodiment, the content of elemental sulfur in the complex is so high that elemental sulfur is present outside the pores of the activated carbon. In this case, the complex may be a lump such as a pellet, but can be powdered by mechanically crushing it.

In one embodiment, the composite contains 150 to 600 parts by mass, 200 to 550 parts by mass, or 220 to 500 parts by mass of elemental sulfur and discharge products of elemental sulfur, calculated as sulfur, per 100 parts by mass of activated carbon. If the amount is 600 parts by mass or less, the sulfur in the activated carbon can be uniformly made conductive, and higher battery performance can be expected when the composite material is used. If the amount is 150 parts by mass or more, a sufficient sulfur content is ensured, and an electrode material with a higher energy density can be obtained.

2. Manufacturing method of the composite A manufacturing method of the composite according to one embodiment of the present invention includes forming a composite of activated carbon having a peak area ratio of an oxygen functional group of 15% or less in a C1s spectrum obtained by X-ray photoelectron spectroscopy and at least one of elemental sulfur and a discharge product of elemental sulfur.
This gives a composite according to one embodiment of the present invention.

In this embodiment, the activated carbon used for the composite has a peak area ratio of oxygen functional groups of 15% or less in the C1s spectrum obtained by X-ray photoelectron spectroscopy. As a method for producing such activated carbon, the methods described below as the first and second embodiments can be used.

First Embodiment
In the first embodiment, a treatment for reducing oxygen functional groups is applied to raw activated carbon, which produces activated carbon having a peak area ratio of oxygen functional groups of 15% or less in a C1s spectrum obtained by X-ray photoelectron spectroscopy.

The activated carbon used as the raw material activated carbon is not particularly limited, but examples thereof include phenolic resin-derived activated carbon obtained by baking and carbonizing spherical phenolic resin, plant-derived carbonized materials such as charcoal, bamboo charcoal, and coconut shell charcoal, carbon derived from petroleum pitch, carbon derived from coal pitch, carbon derived from rayon, and carbon derived from acrylonitrile.
Activated carbon derived from phenolic resin has a high carbon residue rate and is an artificially synthesized resin raw material, so it is highly desirable because its structure can be easily controlled. Carbonized materials derived from plants are expected to have a hierarchical structure derived from the plant-derived structure, and are also desirable from the perspective of decarbonization because the plants occlude carbon dioxide in the air during growth. Carbon derived from petroleum pitch or coal pitch has the advantage of being available in large quantities at low cost.
The raw activated carbon may be subjected to activation treatment such as an alkali activation treatment using an alkali (potassium hydroxide, etc.) For example, the alkali activation treatment may be a method in which activated carbon and potassium hydroxide are kept at a temperature of 500° C. or higher and 1000° C. or lower for 10 to 120 minutes in a nitrogen flow atmosphere.

The raw material activated carbon may have a peak area ratio of more than 15%.
Alternatively, raw activated carbon having a peak area ratio of 15% or less may be used. In this case, the peak area ratio (amount of oxygen functional groups) can be further reduced by a treatment for reducing the amount of oxygen functional groups.

As a treatment for reducing the amount of oxygen functional groups, the raw material activated carbon can be treated (heat treated) at a temperature of 500° C. or more and 1000° C. or less.
The atmosphere during the treatment preferably does not contain oxygen or water vapor.
The atmosphere during the treatment preferably contains an inert gas such as nitrogen (N ₂ ) or argon.
Furthermore, the atmosphere during the treatment preferably contains hydrogen (H ₂ ). By containing hydrogen in the atmosphere during the treatment, radicals on the carbon surface after the functional groups have been removed can be terminated with hydrogen, and re-oxidation after exposure to the atmosphere to generate oxygen functional groups can be suppressed.
When the treatment atmosphere contains hydrogen, the hydrogen concentration is, for example, 10 to 100% by volume, with the remainder preferably being an inert gas such as nitrogen or argon.
It is preferable that the raw activated carbon is subjected to the treatment for reducing the amount of oxygen functional groups alone. Here, "alone" means that an alkali (potassium hydroxide, etc.) used in the alkali activation treatment is not present. Of course, the gas forming the above-mentioned atmosphere may be present.
In one embodiment, the time for the treatment to reduce oxygen functional groups is 1 hour or more, 2 hours or more, 5 hours or more, 7 hours or more, 10 hours or more, 15 hours or more, or 20 hours or more. The upper limit is not particularly limited, and may be, for example, 120 hours or less, 60 hours or less, 48 hours or less, or 36 hours or less.

Second Embodiment
In the second embodiment, the activated carbon is physically activated under pressure, thereby obtaining activated carbon having a peak area ratio of 15% or less (pressure physically activated activated carbon).

The activated carbon used in the pressurized physical activation treatment is not particularly limited, but for example, the activated carbon mentioned above as the raw activated carbon can be used.

Gases used for pressurized physical activation include carbon dioxide, water vapor, oxygen, air, etc. By using carbon dioxide as the gas used for pressurized physical activation, the activation effect is mild and the degree of activation can be easily controlled.
The concentration of carbon dioxide in the gas is, for example, 50 to 100% by volume.

In one embodiment, the pressurized physical activation is carried out under an absolute pressure of 2 atmospheres or more.
In one embodiment, the pressurized physical activation is carried out under a pressure of 2 to 100 atmospheres absolute, 3 to 10 atmospheres absolute, or 5 to 9 atmospheres absolute.

In one embodiment, the time for the pressurized physical activation treatment using carbon dioxide is more than 0 minutes and not more than 99 hours, 1 minute or more and not more than 24 hours, or 5 minutes or more and not more than 8 hours.
The temperature of the pressurized physical activation treatment using carbon dioxide can be appropriately set depending on the pressure, etc., but is preferably 600° C. or higher, more preferably 700° C. or higher, and is preferably 1200° C. or lower, more preferably 1100° C. or lower.

For details of the raw activated carbon (peak area ratio, specific surface area, total pore volume, micropore volume, etc.), the explanation given for the activated carbon in the composite can be used as appropriate.

(compound)
The activated carbon having a peak area ratio of 15% or less obtained in the above manner (raw activated carbon) is composited with at least one of elemental sulfur and discharge products of elemental sulfur.
Here, "composite" means that at least one of elemental sulfur and discharge products of elemental sulfur is attached to the surface of the activated carbon (pore inner surface and pore outer surface). This can mean that the surface of the activated carbon is covered with at least one of elemental sulfur and discharge products of elemental sulfur.

The method for compounding is not particularly limited, and examples thereof include a method in which raw activated carbon is mixed with at least one of elemental sulfur and a discharge product of elemental sulfur, and the mixture is heated.
The heating temperature is not particularly limited, and is, for example, 130 to 445°C, 140 to 400°C, or 150 to 350°C. If the heating temperature is 130°C or higher, the melting point of elemental sulfur (115°C) is exceeded, so sulfur is expected to melt and be impregnated into the activated carbon. The upper limit of the heating temperature is preferably equal to or lower than the boiling point of elemental sulfur (445°C). In particular, lithium polysulfide and lithium sulfide, which are discharge products of elemental sulfur, have high melting points, so the temperature may be higher than 445°C.
The heating time is not particularly limited, and is, for example, 0.1 to 99 hours, 1 to 24 hours, or 2 to 8 hours.

A positive electrode mixture according to an embodiment of the present invention includes the composite according to an embodiment of the present invention or a composite produced by the method for producing a composite according to an embodiment of the present invention, and a sulfide solid electrolyte, which can impart excellent rate characteristics to a lithium ion battery.

(Sulfide solid electrolyte)
The sulfide solid electrolyte is a solid electrolyte that contains at least sulfur atoms and exhibits ionic conductivity due to the metal atoms contained therein, and contains, in addition to sulfur atoms, preferably lithium atoms and phosphorus atoms, more preferably lithium atoms, phosphorus atoms and halogen atoms, and has ionic conductivity due to lithium atoms.
In one embodiment, the solid electrolyte includes at least lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms.
In one embodiment, the solid electrolyte includes lithium atoms, phosphorus atoms, sulfur atoms, bromine atoms, and iodine atoms.
The sulfide solid electrolyte may be an amorphous sulfide solid electrolyte or a crystalline sulfide solid electrolyte.

(Amorphous sulfide solid electrolyte)
The amorphous sulfide solid electrolyte may be used without any particular limitation as long as it contains at least sulfur atoms and exhibits ionic conductivity due to the metal atoms contained therein. Representative examples include solid electrolytes containing sulfur atoms, lithium atoms, and phosphorus atoms, such as Li ₂ S-P ₂ S ₅ , which are composed of lithium sulfide and phosphorus sulfide; solid electrolytes composed of lithium sulfide, phosphorus sulfide, and lithium halide, such as Li ₂ S-P _{2 S 5} -LiI, Li ₂ S-P ₂ S ₅ -LiCl, Li ₂ S-P ₂ S 5 -LiBr, and Li ₂ S-P 2 S ₅ -LiI-LiBr; and solid electrolytes further containing other elements such as oxygen and silicon _, such as Li ₂ S-P ₂ S ₅ -Li ₂ O-LiI and Li ₂ S-SiS ₂ -P ₂ S _5. In order to obtain a higher ionic conductivity, a solid electrolyte composed of lithium sulfide, phosphorus sulfide, and a lithium halide, such as Li ₂ S-P ₂ S ₅ -LiI, Li ₂ S-P ₂ S ₅ -LiCl, Li ₂ S-P ₂ S ₅ -LiBr, or Li ₂ S-P ₂ S ₅ -LiI-LiBr, is preferred.
The types of elements constituting the amorphous sulfide solid electrolyte can be confirmed, for example, by an ICP emission spectroscopic analyzer.

When the amorphous sulfide solid electrolyte has at least Li ₂ S-P ₂ S ₅ , the molar ratio of Li ₂ S to P ₂ S ₅ is preferably 30 to 85:15 to 70, more preferably 40 to 80:20 to 60, and even more preferably 45 to 78:22 to 55, from the viewpoint of obtaining high chemical stability and higher ionic conductivity.
When the amorphous sulfide solid electrolyte is, for example, Li ₂ S-P ₂ S ₅ -LiI-LiBr, the total content of lithium sulfide and diphosphorus pentasulfide is preferably 30 to 95 mol%, more preferably 35 to 90 mol%, and even more preferably 40 to 85 mol%. The ratio of lithium bromide to the total of lithium bromide and lithium iodide is preferably 1 to 99 mol%, more preferably 20 to 90 mol%, even more preferably 40 to 80 mol%, and particularly preferably 50 to 70 mol%.

The shape of the amorphous sulfide solid electrolyte is not particularly limited, but may be, for example, particulate. The average particle size (D ₅₀ ) of the particulate amorphous sulfide solid electrolyte may be, for example, within a range of 0.01 μm to 500 μm, or 0.1 to 200 μm.
In this specification, the average particle size ( _D50 ) is the particle size that reaches 50% of the total when the particle size distribution cumulative curve is drawn, starting from the smallest particle, and the volume distribution is the average particle size that can be measured using, for example, a laser diffraction/scattering type particle size distribution measuring device.

(Crystalline sulfide solid electrolyte)
The crystalline sulfide solid electrolyte may be, for example, a so-called glass ceramic obtained by heating the above-mentioned amorphous sulfide solid electrolyte to a crystallization temperature or higher, and a sulfide solid electrolyte having the following crystal structure may be used.
Examples of crystal structures that the crystalline sulfide solid electrolyte containing lithium atoms, sulfur atoms, and phosphorus atoms may have include a Li ₃ PS ₄ crystal structure, a Li ₄ P ₂ S ₆ crystal structure, a Li ₇ PS ₆ crystal structure, a Li ₇ P ₃ S ₁₁ crystal structure, and a crystal structure having peaks at 2θ = approximately 20.2° and approximately 23.6° (for example, JP 2013-16423 A).

In addition, examples of the crystal structure that the crystalline sulfide solid electrolyte containing lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms may have include the above-mentioned Li _4-x Ge _1-x P _x S ₄ -based thio-lisicon region II (thio-LISICON Region II) type crystal structure and a crystal structure similar to the Li _4-x Ge _1-x P _x S ₄ -based thio-lisicon region II (thio-LISICON Region II) type.

In an X-ray diffraction measurement using CuKα radiation, the diffraction peaks of the Li ₃ PS ₄ crystal structure appear, for example, at 2θ=17.5°, 18.3°, 26.1°, 27.3°, and 30.0°, the diffraction peaks of the Li ₄ P ₂ S ₆ crystal structure appear, for example, at 2θ=16.9°, 27.1°, and 32.5°, the diffraction peaks of the Li ₇ PS ₆ crystal structure appear, for example, at 2θ=15.3°, 25.2°, 29.6°, and 31.0°, the diffraction peaks of the Li ₇ P ₃ S ₁₁ crystal structure appear, for example, at 2θ=17.8°, 18.5°, 19.7°, 21.8°, 23.7°, 25.9°, 29.6°, and 30.0°, and the diffraction peaks of the Li _4-x Ge _1-x P The diffraction peaks of the _{Li4- xGe1-xPxS4-type thio-LISICON Region II crystal structure appear, for example, at 2θ = 20.1°, 23.9°, and 29.5°, and the diffraction peaks of a crystal structure similar to the Li4-xGe1 - xPxS4 - type} thio-LISICON Region II crystal structure appear, for example, at 2θ = 20.2° and 23.6°. These peak positions may vary within a range of ±0.5°.

The crystal structure of the crystalline sulfide solid electrolyte also includes an argyrodite crystal structure. Examples of the argyrodite crystal structure include a Li ₇ PS ₆ crystal structure, a crystal structure represented by the composition formula Li _{7 -x} P _{1 -y} Si _y S ₆ and Li _7+x P _1-y Si _y S ₆ (x is −0.6 to 0.6, y is 0.1 to 0.6) having a Li 7 PS 6 structural skeleton, a crystal structure represented by Li _7-x-2y PS _6-x-y Cl _x (0.8≦x≦1.7, 0<y≦−0.25x+0.5), and a crystal structure represented by Li _7-x PS _6-x Ha _x (Ha is Cl or Br, x is preferably 0.2 to 1.8).

Among the above crystal structures, the crystal structure possessed by the crystalline sulfide solid electrolyte is preferably a Li ₃ PS ₄ crystal structure, a thiolicon region II type crystal structure, or an argyrodite type crystal structure.

The shape of the crystalline sulfide solid electrolyte is not particularly limited, but may be, for example, particulate. The average particle size (D ₅₀ ) of the particulate crystalline sulfide solid electrolyte may be, for example, within a range of 0.01 μm to 500 μm, or 0.1 to 200 μm, similar to the average particle size (D ₅₀ ) of the amorphous sulfide solid electrolyte described above.

In one embodiment, the positive electrode mixture contains 40 mass % or more of elemental sulfur and discharge products of elemental sulfur in terms of sulfur. Here, the elemental sulfur and discharge products of elemental sulfur are derived from the above-mentioned complex.
In one embodiment, the positive electrode mixture contains 40 to 90 mass %, 40 to 70 mass %, or 40 to 60 mass % of elemental sulfur and discharge products of elemental sulfur, calculated as sulfur. Here, the elemental sulfur and discharge products of elemental sulfur are derived from the above-mentioned complex.

4. Lithium-ion battery positive electrode and lithium-ion battery A lithium-ion battery positive electrode according to one embodiment of the present invention includes the positive electrode mixture according to one embodiment of the present invention.
The positive electrode for a lithium ion battery according to this embodiment can impart excellent rate characteristics to the lithium ion battery.

A lithium ion battery according to an embodiment of the present invention includes a lithium ion battery positive electrode according to an embodiment of the present invention.
The lithium ion battery according to this embodiment has the effect of providing excellent rate characteristics.

The cathode mixture can be used as the cathode layer of a lithium ion battery, other components of which are known in the art, and the anode layer can be selected so that the anode active material does not include lithium ions.
The negative electrode active material contained in the negative electrode layer of the lithium ion battery can be a "negative electrode active material containing lithium ions". Also, the negative electrode active material contained in the negative electrode layer of the lithium ion battery may be a "negative electrode active material that supplies lithium ions to the positive electrode".

There are no particular limitations on the negative electrode of a lithium-ion battery, so long as it is one that can be used in normal batteries. The negative electrode may be made of a negative electrode composite material that is a mixture of a negative electrode active material and a solid electrolyte.

As the negative electrode active material, commercially available products can be used. For example, carbon materials, Sn metal, In metal, Si metal, Li metal, alloys of these metals, etc. can be used. Specifically, natural graphite, various graphites, lithium titanate, metal powders such as Si, Sn, Al, Sb, Zn, Bi, metal alloys such as SiAl, Sn ₅ Cu ₆ , Sn ₂ Co, Sn ₂ Fe, and other amorphous alloys and plated alloys can be mentioned. There is no particular restriction on the particle size, but those with an average particle size of several μm to 80 μm can be suitably used.

The electrolyte layer is not particularly limited, and any known electrolyte can be used. For example, oxide solid electrolytes, sulfide solid electrolytes, and polymer electrolytes are preferred, and sulfide solid electrolytes are more preferred from the viewpoint of ionic conductivity. The sulfide solid electrolyte is preferably one used in the positive electrode composite material described above.

The method for manufacturing the lithium ion battery is not particularly limited. For example, a method may be used in which a sheet is formed on a positive electrode current collector with a positive electrode layer made of one or more selected from the group consisting of the positive electrode composite material according to one embodiment of the present invention and the positive electrode composite material according to another embodiment of the present invention, a solid electrolyte layer is formed on the sheet, and the sheet on which the negative electrode layer is formed is laminated on a previously formed negative electrode current collector, and pressed.

5. Activated Carbon for All-Solid-State Lithium-Ion Batteries The activated carbon for all-solid-state lithium-ion batteries according to one embodiment of the present invention has a peak area ratio of oxygen functional groups in a C1s spectrum obtained by X-ray photoelectron spectroscopy of 15% or less.
The activated carbon for an all-solid-state lithium-ion battery according to this embodiment can impart excellent rate characteristics to the all-solid-state lithium-ion battery.

6. Use of Activated Carbon In one embodiment of the present invention, activated carbon having a peak area ratio of oxygen functional groups in a C1s spectrum obtained by X-ray photoelectron spectroscopy of 15% or less is used in an all-solid-state lithium ion battery.
This enables the all-solid-state lithium-ion battery to have excellent rate characteristics.

7. Method for Producing an All-Solid-State Lithium-Ion Battery A method for producing an all-solid-state lithium-ion battery according to one embodiment of the present invention includes subjecting activated carbon to a treatment at a temperature of 500° C. or higher and 1000° C. or lower to reduce oxygen functional groups.
This enables the all-solid-state lithium-ion battery to have excellent rate characteristics.

The following describes examples of the present invention, but the present invention is not limited to these examples.

(Production Example 1)
"Creating activated carbon 1"
A spherical phenolic resin (spherical phenolic resin BEAPS, manufactured by Asahi Organic Chemicals Co., Ltd., particle size 8 μm) was heated in a tubular electric furnace in a nitrogen flow atmosphere (200 mL/min) at a temperature rise of 5° C./min to 600° C., and then held for 1 hour to be carbonized, thereby obtaining a phenolic resin-derived carbon (activated carbon before activation).
The obtained phenol resin-derived carbon and potassium hydroxide in an amount six times the amount of carbon were placed in a Ni crucible, which was then placed in a stainless steel container and heated to 800° C. at a rate of 5° C./min in a nitrogen flow atmosphere (100 mL/min) using an electric furnace, and maintained at that temperature for 1 hour for activation. The carbon was neutralized with hydrochloric acid, washed with water until the pH reached 7, and then dried to obtain activated carbon (alkali-activated activated carbon) 1.

(Production Example 1-1)
"Functional group reduction treatment of activated carbon 1 in a hydrogen atmosphere"
Activated carbon 1 (0.5 g) was treated with hydrogen (50 sccm) and argon (200 sccm) at 600° C. for 24 hours to reduce the amount of functional groups, thereby obtaining activated carbon 1-1.

(Production Example 1-2)
"Treatment of activated carbon 1 in an ozone atmosphere to increase functional groups"
0.4 g of activated carbon 1 was treated with an NZR-60MF manufactured by Roki Techno Co., Ltd. at an oxygen supply rate of 1 L/min and an ozone concentration of 20 g/ ^m3 at room temperature for 1 hour to give functional groups, thereby obtaining activated carbon 1-2.

(Production Example 2)
"Creating activated carbon 2"
Spherical phenolic resin (manufactured by Asahi Organic Chemicals Co., Ltd., particle size 17 μm) was heated in a tubular electric furnace in a nitrogen flow atmosphere (200 mL/min) to 600° C. at a rate of 5° C./min, and then held for 1 hour for carbonization to obtain phenolic resin-derived carbon (activated carbon before activation).
The obtained phenol resin-derived carbon was pressurized to 1.0 MPa (10 atm) in a tubular electric furnace with a carbon dioxide flow rate of 100 to 200 mL/min, and the temperature was raised to 1000° C. at a rate of 5° C./min, and then activated for 30 minutes to obtain activated carbon (pressurized carbon dioxide activated activated carbon) 2.

(Production Example 3)
"Creating Activated Carbon 3"
Spherical phenolic resin (manufactured by Asahi Organic Chemicals Co., Ltd., particle size 17 μm) was heated in a tubular electric furnace in a nitrogen flow atmosphere (200 mL/min) to 600° C. at a rate of 5° C./min, and then held for 1 hour for carbonization to obtain phenolic resin-derived carbon (activated carbon before activation).
The obtained phenol resin-derived carbon was pressurized to 1.0 MPa (10 atm) in a tubular electric furnace with a carbon dioxide flow rate of 100 to 200 mL/min, and the temperature was raised to 1000° C. at a rate of 5° C./min, and then activated for 1 hour to obtain activated carbon (pressurized carbon dioxide activated activated carbon) 3.

(Production Example 4)
"Creating Activated Carbon 4"
Spherical phenolic resin (manufactured by Asahi Organic Chemicals Co., Ltd., particle size 8 μm) was heated in a tubular electric furnace in a nitrogen flow atmosphere (200 mL/min) to 600° C. at a rate of 5° C./min, and then held for 1 hour for carbonization, thereby obtaining phenolic resin-derived carbon (activated carbon before activation).
The obtained phenol resin-derived carbon was pressurized to 1.0 MPa (10 atm) in a tubular electric furnace with a carbon dioxide flow rate of 100 to 200 mL/min, and the temperature was raised to 1000° C. at a rate of 5° C./min, and then activated for 20 minutes to obtain activated carbon (pressurized carbon dioxide activated activated carbon) 4.

Example 1
・Preparation of composite powder (composite) "Preparation of composite powder A"
Activated carbon 1-1 and sulfur (S) were placed in a glass bottle in a weight ratio of 1:5, and the bottle was sealed in a SUS tube container. The bottle was heated in an electric furnace at 150° C. for 6 hours and at 300° C. for 2.75 hours to obtain a composite powder A of activated carbon and sulfur.

・Preparation of positive electrode mixture "Preparation of solid electrolyte"
0.4127 g of lithium sulfide, 0.6655 g of diphosphorus pentasulfide, 0.2137 g of lithium iodide, 0.2080 g of lithium bromide, and 10 zirconia balls with a diameter of 10 mm were placed in a 45 mL zirconia pot and sealed. Using a planetary ball mill (manufactured by Fritsch, model number P-7), the mixture was mixed (mechanical milling) at a rotation speed of 370 rpm for 40 hours to obtain a powder. The obtained powder was heated at 195° C. for 3 hours to obtain a solid electrolyte.

"Preparation of positive electrode composite powder"
0.2 g of the composite powder A and 0.2 g of the solid electrolyte were placed in a 45 mL zirconia pot together with 10 zirconia balls having a diameter of 10 mm and sealed. The mixture was milled using a planetary ball mill (manufactured by Fritsch, model number P-7) at a rotation speed of 370 rpm for 20 hours to obtain a positive electrode composite powder.

・Preparation of lithium ion battery (all solid state) 100 mg of the solid electrolyte prepared above was put into a cylinder made of Macol with a diameter of 10 mm and pressure molded. The positive electrode composite powder prepared above was put into the pressurized surface so that the sulfur amount was 3.5 mg, and pressure molded again. On the pressurized surface opposite to the positive electrode composite, lithium titanate ("LT-112" manufactured by Ishihara Sangyo Kaisha), conductive assistant ("Li-100" manufactured by Denka Co., Ltd., powdered acetylene black), and Li ₂ S-P ₂ S ₅ -LiCl-LiBr type solid electrolyte B were mixed in a mortar in a mass ratio of 60:5:35 for 5 minutes. 166 mg of negative electrode composite (also called "LTO (lithium titanate) negative electrode composite") was put into the pressurized surface opposite to the positive electrode composite, and then lithium foil was further put in and pressed to prepare an all solid state battery.

Example 2
A composite powder, a positive electrode mixture, and a lithium ion battery were produced in the same manner as in Example 1, except that activated carbon 2 was used instead of activated carbon 1-1.

Example 3
A composite powder, a positive electrode mixture, and a lithium ion battery were produced in the same manner as in Example 1, except that activated carbon 3 was used instead of activated carbon 1-1.

Example 4
A composite powder, a positive electrode mixture, and a lithium ion battery were produced in the same manner as in Example 1, except that Activated Carbon 4 was used instead of Activated Carbon 1-1.

(Comparative Example 1)
A composite powder, a positive electrode mixture, and a lithium ion battery were produced in the same manner as in Example 1, except that activated carbon 1 was used instead of activated carbon 1-1.

(Comparative Example 2)
A composite powder, a positive electrode mixture, and a lithium ion battery were produced in the same manner as in Example 1, except that the activated carbon 1-2 was used instead of the activated carbon 1-1.

Test and Evaluation Methods (1) Evaluation of Battery Characteristics A constant current charge/discharge test was carried out on the all-solid-state batteries obtained in the Examples and Comparative Examples. The cutoff potential of the constant current test was set to −0.4 to +1.3 V vs. Li-LTO, and the current value was set as shown in Table 1 below.

The discharge capacity per unit mass of sulfur (capacity at 1C [mAh/g]) was calculated at the 8th cycle (discharge current value: 5.86 mA).

(2) Measurement of the amount of functional groups in activated carbon The amount of oxygen functional groups (peak area ratio [%] of oxygen functional groups in the C1s spectrum) was determined by obtaining the C1s spectrum of activated carbon using XPS and performing waveform separation with reference to Patent No. 5966222. The XPS measurement device and measurement conditions are as follows:
<XPS measurement device and measurement conditions>
Measurements were performed using a transfer vessel to prevent the sample from being exposed to the atmosphere.
Equipment: ULVAC-PHI VersaProbe II
Excitation X-ray: Al ray, monochrome 14 kV
X-ray diameter/output: 100μm 100W
Analysis area: 200 μm x 1200 μm
Pass energy: 23.5 eV
Step energy: 0.1 eV
Photoelectron detection angle: 45°
Horizontal axis (bond energy): Charge neutralization correction with C1s at 284.2 eV

(3) Measurement of specific surface area, micropore volume, and total pore volume of activated carbon The specific surface area, micropore volume, and total pore volume of the activated carbon used in the preparation of the composite (activated carbon of each production example) were measured using a pore distribution measuring device "Autosorb-3" manufactured by Quantacrome or "Nova" manufactured by Anton Paar with reference to Carbon 1997 No. 197 159-166, and analyzed by the α _s method.
In order to standardize the analytical results, the analysis of the outside of the particles and the mesopores by the α _s method was performed in the range of α _s =1 to 2 for all samples.
The results are shown in Table 2.

From Table 2, it can be seen that Examples 1 to 4, which have a smaller amount of oxygen functional groups, have better battery characteristics (larger capacity) than Comparative Examples 1 and 2.

Although some embodiments and/or examples of the present invention have been described in detail above, those skilled in the art can easily make many modifications to these exemplary embodiments and/or examples without substantially departing from the novel teachings and advantages of the present invention, and therefore many such modifications are within the scope of the present invention.
The contents of all documents cited in this specification and of the application from which this application claims priority under the Paris Convention are incorporated by reference in their entirety.

Claims (16)

Activated carbon having a peak area ratio of oxygen functional groups in a C1s spectrum obtained by X-ray photoelectron spectroscopy of 15% or less;
A composite material comprising: at least one of elemental sulfur and a discharge product of elemental sulfur. The composite according to claim 1 , wherein the activated carbon has a specific surface area of 2300 m ² /g or more. The composite according to claim 1 or 2, wherein the activated carbon has a total pore volume of 1.2 cc/g or more. The composite according to any one of claims 1 to 3, wherein the activated carbon has a micropore volume of 1.2 cc/g or more. Activated carbon having a peak area ratio of oxygen functional groups in a C1s spectrum obtained by X-ray photoelectron spectroscopy of 15% or less;
A method for producing a composite comprising: combining elemental sulfur and at least one of a discharge product of elemental sulfur. The method for producing a composite according to claim 5, wherein the activated carbon has a specific surface area of 2300 m ² /g or more. The method for producing a composite according to claim 5 or 6, wherein the activated carbon has a total pore volume of 1.2 cc/g or more. The method for producing a composite according to any one of claims 5 to 7, wherein the activated carbon has a micropore volume of 1.2 cc/g or more. The method for producing a composite according to any one of claims 5 to 8, wherein the activated carbon is treated to reduce oxygen functional groups at a temperature of 500°C or higher and 1000°C or lower. A composite according to any one of claims 1 to 4, or a composite produced by the method for producing a composite according to any one of claims 5 to 9;
A positive electrode composite comprising: a sulfide solid electrolyte; The positive electrode mixture according to claim 10, wherein the sulfide solid electrolyte contains at least lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms. A positive electrode for a lithium ion battery comprising the positive electrode mixture according to claim 10 or 11. A lithium ion battery comprising the positive electrode mixture according to claim 10 or 11. Activated carbon for all-solid-state lithium-ion batteries, in which the peak area ratio of oxygen functional groups in the C1s spectrum obtained by X-ray photoelectron spectroscopy is 15% or less. The use of activated carbon in an all-solid-state lithium-ion battery, in which the peak area ratio of oxygen functional groups in the C1s spectrum obtained by X-ray photoelectron spectroscopy is 15% or less. A method for manufacturing an all-solid-state lithium-ion battery, comprising treating activated carbon at a temperature of 500°C or higher and 1000°C or lower to reduce oxygen functional groups.