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

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, manufacturing method of composite, cathode mixture, cathode for lithium ion battery, lithium ion battery, activated carbon for all-solid-state lithium ion battery, use of activated carbon, and manufacturing method of all-solid-state lithium ion battery

[0001] The present invention relates to a composite, 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. Specifically, the present invention relates to a composite that can improve rate characteristics, 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.

[0002] The use of a sulfur-activated carbon composite for the positive electrode of an all-solid-state lithium-ion battery has been proposed. On the other hand, it has been reported that the performance of a liquid-phase lithium-ion battery can be improved by increasing the oxygen functional group of the activated carbon used in the sulfur-activated carbon composite (Non-Patent Document 1).

[0003] Performance Enhancement of Rechargeable Sulfur Cathode Utilizing Microporous Activated Carbon Composite, Electrochemistry, 2017, 85(10), pp. 671-674

[0004] 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 simply referred to as "composite") in the positive electrode from the viewpoint of the activated carbon used. Conventional techniques such as Non-Patent Document 1 have not been able to solve this problem.

[0005] An object of the present invention is to provide a composite that can improve rate characteristics, particularly when used in a positive electrode of an all-solid-state lithium ion battery, 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.

[0006] As a result of extensive research, the present inventors have found that the rate characteristics of all-solid-state lithium-ion batteries and the like can be improved when activated carbon with a reduced amount of oxygen functional groups is used as the activated carbon used in the sulfur-activated carbon composite, and have completed the present invention. According to the present invention, the following composites and the like can be provided: 1. A composite comprising 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, and at least one of elemental sulfur and a discharge product of elemental sulfur. 2. A composite comprising activated carbon having a specific surface area of ​​2,300 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. A method for producing a composite, comprising: combining 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 with at least one of elemental sulfur and a discharge product of elemental sulfur. 6. The activated carbon has a specific surface area of ​​2,300 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 treated to reduce oxygen functional groups at a temperature of 500°C or more and 1000°C or less. 10. A cathode mixture comprising: the 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, and a sulfide solid electrolyte. 11. The cathode mixture according to 10, wherein the sulfide solid electrolyte contains at least a lithium atom, a phosphorus atom, a sulfur atom, and a halogen atom. 12. A cathode for a lithium ion battery, comprising the cathode mixture according to 10 or 11. 13. A lithium ion battery, comprising the cathode mixture according to 10 or 11. 14. 14. Activated carbon for an all-solid-state lithium-ion battery, wherein the peak area ratio of oxygen functional groups in a C1s spectrum obtained by X-ray photoelectron spectroscopy is 15% or less. 15. Use of activated carbon, wherein the peak area ratio of oxygen functional groups in a C1s spectrum obtained by X-ray photoelectron spectroscopy is 15% or less, for use in an all-solid-state lithium-ion battery. 16. A method for producing an all-solid-state lithium-ion battery, comprising treating the activated carbon at a temperature of 500°C or higher and 1000°C or lower to reduce the oxygen functional groups.

[0007] According to the present invention, it is possible to provide a composite that can improve rate characteristics, particularly when used in a 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.

[0008] The composite, manufacturing method of the composite, cathode composite, lithium ion battery cathode, lithium ion battery, activated carbon for all-solid-state lithium ion batteries, use of activated carbon, and manufacturing method of all-solid-state lithium ion batteries of the present invention are described in detail below. In this specification, "x to y" represents a numerical range of "x or more and y or less." The upper and lower limits of the numerical ranges can be arbitrarily combined. Furthermore, among the individual embodiments of the aspects of the present invention described below, two or more mutually exclusive embodiments can be combined, and an embodiment combining two or more embodiments is also an embodiment of the aspects of the present invention.

[0009] 1. Composite A composite according to one embodiment of the present invention includes 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 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, i.e., a low amount of oxygen functional groups. As described above, it has been reported that in liquid-type lithium-ion batteries, the performance improves with an increase in the amount of oxygen functional groups in the activated carbon used in the sulfur-activated carbon composite. However, surprisingly, it has been found that in all-solid-state systems, the rate performance improves with a decrease in the amount of oxygen functional groups. The reason for this effect is not necessarily clear, but it is presumed that the low amount of oxygen functional groups suppresses deterioration of the sulfide solid electrolyte and improves the electronic conductivity of the activated carbon.

[0010] (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.

[0011] In one embodiment, the specific surface area of ​​the activated carbon is 1500 m ２ / g or more, 1600m ２ / g or more, 1700m ２ / g or more, 1800m ２ / g or more, 1900m ２ / g or more, 2000m ２ / g or more, 2100m ２ / g or more, 2200m ２ / g or more or 2300m ２ / g or more. The upper limit is not particularly limited, and for example, ２ / g or less, 3000m ２ / g or less or 2800m ２ In one embodiment, the specific surface area of ​​the activated carbon is 2300 m ２ / g or more. This makes it possible to more significantly improve the rate characteristics. The specific surface area is a value measured by the method described in the examples.

[0012] In one embodiment, the activated carbon is activated carbon that has been subjected to a treatment to reduce oxygen functional groups at a temperature of 500° C. to 1000° C. The “treatment to reduce oxygen functional groups” will be described in detail later.

[0013] In one embodiment, the activated carbon is a pressurized physically activated activated carbon. The term "pressurized physically activated activated carbon" will be described in detail later.

[0014] 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 activated carbon, such as general steam-activated 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.

[0015] 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 activated carbon, is less than 1.2 cc / g, which limits the amount of sulfur that can be stored in the activated carbon. In contrast, activated carbon having a micropore volume of 1.2 cc / g or more is preferred because it can store more sulfur in the activated carbon.

[0016] (Elemental sulfur and discharge products of elemental sulfur) The elemental sulfur (sulfur) is not particularly limited, but preferably has a purity of 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), amorphous sulfur, etc. These may be used alone or in combination of two or more. Elemental sulfur becomes a molten liquid when heated.

[0017] During the battery reaction, part or all of the elemental sulfur is converted into discharge products. 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 sulfur contained in the elemental sulfur and the discharge product. The discharge product of elemental sulfur is Li in a fully discharged state. ２ S and its intermediate stage lithium polysulfide Li２ S ２ , Li ２ S ４ , Li ２ S ６ , Li ２ S ８ etc.

[0018] In one embodiment, in the composite, some or all of the elemental sulfur is attached (impregnated) within the pores of the activated carbon. Furthermore, the elemental sulfur that is not impregnated within the pores is present so as to coat part or all of the activated carbon. Whether sulfur is impregnated within 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 the sulfur element. In one embodiment, due to the high content of elemental sulfur in the composite, elemental sulfur is also present outside the pores of the activated carbon. In this case, the composite may be in the form of a pellet-like mass, but can be powdered by mechanically pulverizing it.

[0019] In one embodiment, the composite contains 150 to 600 parts by weight, 200 to 550 parts by weight, or 220 to 500 parts by weight of elemental sulfur and discharge products of elemental sulfur per 100 parts by weight of activated carbon. If the amount is 600 parts by weight or less, the sulfur in the activated carbon can be uniformly imparted with conductivity, and higher battery performance can be expected when combined. If the amount is 150 parts by weight or more, a sufficient sulfur content can be ensured, resulting in an electrode material with a higher energy density.

[0020] 2. Manufacturing Method of Composite A manufacturing method of a composite according to one aspect of the present invention includes combining 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 with at least one of elemental sulfur and a discharge product of elemental sulfur, thereby obtaining a composite according to one aspect of the present invention.

[0021] In this embodiment, the activated carbon to be composited has a peak area ratio of oxygen functional groups of 15% or less in a C1s spectrum obtained by X-ray photoelectron spectroscopy. As a method for producing such activated carbon, the methods described below as a first embodiment and a second embodiment can be used.

[0022] In the first embodiment, a raw activated carbon is subjected to a treatment for reducing oxygen functional groups, thereby producing 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.

[0023] The activated carbon used as the raw activated carbon is not particularly limited, but examples include phenolic resin-derived activated carbon obtained by calcining and carbonizing spherical phenolic resin; plant-derived carbonized materials such as charcoal, bamboo charcoal, and coconut shell charcoal; petroleum pitch-derived carbon; coal pitch-derived carbon; rayon-derived carbon; and acrylonitrile-derived carbon. Phenolic resin-derived activated carbon has a high residual carbon content and is an artificially synthesized resin raw material, making it highly controllable. Furthermore, plant-derived carbonized materials are expected to exhibit a hierarchical structure derived from plant-derived structures and are also desirable from the perspective of decarbonization, as they occlude carbon dioxide from the air during plant growth. Petroleum pitch- and coal pitch-derived carbons also have the advantage of being inexpensive and available in large quantities. The raw activated carbon may be subjected to an activation treatment, such as an alkali activation treatment using an alkali (e.g., potassium hydroxide). For example, an alkali activation treatment can be performed by holding activated carbon and potassium hydroxide in a nitrogen-flowing atmosphere at a temperature of 500°C to 1000°C for 10 to 120 minutes.

[0024] The raw activated carbon may have a peak area ratio of more than 15%. Alternatively, the raw activated carbon may have a peak area ratio of 15% or less. In this case, the peak area ratio (amount of oxygen functional groups) can be further reduced by a treatment to reduce the amount of oxygen functional groups.

[0025] As a treatment for reducing the amount of oxygen functional groups, the raw activated carbon can be treated (heat treated) at a temperature of 500°C or higher and 1000°C or lower. The atmosphere during the treatment preferably does not contain oxygen or water vapor. In addition, the atmosphere during the treatment preferably does not contain nitrogen (N ２ It is preferable that the atmosphere during the treatment contains an inert gas such as hydrogen (H ２ It is preferable that the atmosphere during the treatment contains hydrogen. By including hydrogen in the treatment atmosphere, radicals on the carbon surface after functional groups have been removed can be terminated with hydrogen, thereby preventing re-oxidation and the generation of oxygen functional groups after exposure to the atmosphere. When the treatment atmosphere contains hydrogen, the hydrogen concentration is, for example, 10 to 100% by volume. The balance is preferably an inert gas such as nitrogen or argon. The raw activated carbon is preferably subjected alone to the treatment to reduce the amount of oxygen functional groups. Here, "alone" means that alkali (e.g., potassium hydroxide) used in alkali activation treatment is not present. Of course, the gas forming the above-mentioned atmosphere may also be present. In one embodiment, the treatment time for reducing 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.

[0026] Second Embodiment In a second embodiment, activated carbon is physically activated under pressure, thereby obtaining activated carbon (pressure-physically activated activated carbon) having a peak area ratio of 15% or less.

[0027] The activated carbon to be subjected to the pressure physical activation treatment is not particularly limited, but for example, the activated carbons mentioned above as the raw activated carbon can be used.

[0028] Gases used for pressure physical activation include carbon dioxide, water vapor, oxygen, air, etc. By using carbon dioxide as the gas used for pressure 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.

[0029] In one embodiment, the pressure physical activation is carried out under an absolute pressure of 2 atmospheres or more. In another embodiment, the pressure physical activation is carried out under an absolute pressure of 2 to 100 atmospheres, 3 to 10 atmospheres, or 5 to 9 atmospheres.

[0030] In one embodiment, the time for the pressure 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 for the pressure physical activation treatment using carbon dioxide can be appropriately set depending on the pressure, etc., but is preferably 600°C or more, more preferably 700°C or more. In addition, the temperature is preferably 1200°C or less, more preferably 1100°C or less.

[0031] For details of the raw material activated carbon (such as peak area ratio, specific surface area, total pore volume, and micropore volume), the explanation given for the activated carbon in the composite can be used as appropriate.

[0032] (Complexation) The activated carbon (raw activated carbon) having a peak area ratio of 15% or less obtained as described above is composited with at least one of elemental sulfur and discharge products of elemental sulfur. Here, "complexation" means that at least one of elemental sulfur and discharge products of elemental sulfur is attached to the surface of the activated carbon (the inner surface of the pores and the outer surface of the pores). This can mean that the surface of the activated carbon is coated with at least one of elemental sulfur and discharge products of elemental sulfur.

[0033] The method of compositing is not particularly limited, and examples include a method of mixing raw activated carbon with at least one of elemental sulfur and discharge products of elemental sulfur and heating. 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, and sulfur melts, and impregnation into the activated carbon can be expected. 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 even 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.

[0034] A cathode composite according to an aspect of the present invention includes the composite according to an aspect of the present invention or a composite produced by the method for producing a composite according to an aspect of the present invention, and a sulfide solid electrolyte, thereby imparting excellent rate characteristics to a lithium ion battery.

[0035] (Sulfide solid electrolyte) The sulfide solid electrolyte is a solid electrolyte that contains at least sulfur atoms and exhibits ionic conductivity due to the contained metal atoms. In addition to sulfur atoms, the sulfide solid electrolyte preferably contains 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 contains at least lithium atoms, phosphorus atoms, sulfur atoms, and halogen atoms. In one embodiment, the solid electrolyte contains 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.

[0036] (Amorphous sulfide solid electrolyte) The amorphous sulfide solid electrolyte can be used without any particular limitation as long as it contains at least sulfur atoms and exhibits ionic conductivity due to the contained metal atoms. Representative examples include Li ２ S-P ２ S ５ a solid electrolyte containing sulfur atoms, lithium atoms, and phosphorus atoms, which is composed of lithium sulfide and phosphorus sulfide 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, Li ２ S-P ２ S ５ -LiI-LiBr, etc., solid electrolytes composed of lithium sulfide, phosphorus sulfide, and lithium halide; and solid electrolytes further containing other elements such as oxygen and silicon, for example, Li ２ S-P ２ S５ -Li ２ O-LiI, Li ２ S-SiS ２ -P ２ S ５ In order to obtain higher ionic conductivity, a solid electrolyte 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, Li ２ S-P ２ S ５ A solid electrolyte composed of lithium sulfide, phosphorus sulfide, and lithium halide, such as LiI-LiBr, is preferred. The types of elements constituting the amorphous sulfide solid electrolyte can be confirmed, for example, by an ICP emission spectrometer.

[0037] The amorphous sulfide solid electrolyte contains at least Li ２ S-P ２ S ５ When Li ２ S and P ２ S ５ From the viewpoint of obtaining high chemical stability and higher ionic conductivity, the molar ratio of Li to Li 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. ２ S-P ２ S ５ In the case of -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%.

[0038] The shape of the amorphous sulfide solid electrolyte is not particularly limited, but may be, for example, particulate. The average particle diameter (D ５０ ) can be, for example, in the range of 0.01 μm to 500 μm, or 0.1 to 200 μm. ５０ ) is the particle size at which 50% of the total particle size is reached when the particle size distribution integral curve is drawn and the integral is calculated from the smallest particle size, and the volume distribution is an average particle size that can be measured using, for example, a laser diffraction / scattering particle size distribution measuring device.

[0039] (Crystalline sulfide solid electrolyte) The crystalline sulfide solid electrolyte may be, for example, a so-called glass ceramic obtained by heating the amorphous sulfide solid electrolyte to a temperature equal to or higher than the crystallization temperature, 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 Li ３ P.S. ４ Crystal structure, Li ４ P ２ S ６ Crystal structure, Li ７ P.S. ６ Crystal structure, Li ７ P ３ S １１ Examples of such structures include a crystal structure having peaks at 2θ=approximately 20.2° and 23.6° (for example, JP 2013-16423 A).

[0040] The crystalline sulfide solid electrolyte containing lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms may have the following crystalline structure: ４－ｘ Ge １－ｘ P ｘ S ４ Thio-LISICON Region II crystal structure, Li ４－ｘ Ge １－ｘ P ｘ S ４ Examples include a crystal structure similar to that of thio-LISICON Region II type.

[0041] In X-ray diffraction measurement using CuKα radiation, Li ３ P.S. ４ Diffraction peaks of the crystal structure appear, for example, at 2θ=17.5°, 18.3°, 26.1°, 27.3°, and 30.0°. ４ P ２ S ６ Diffraction peaks of the crystal structure appear, for example, at 2θ=16.9°, 27.1°, and 32.5°. ７ P.S. ６ Diffraction peaks of the crystal structure appear, for example, at 2θ=15.3°, 25.2°, 29.6°, and 31.0°. ７ P ３ S １１ Diffraction peaks of the 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 Li ４－ｘ Ge １－ｘ P ｘ S ４ The diffraction peaks of the thio-LISICON Region II crystal structure appear, for example, at 2θ=20.1°, 23.9°, and 29.5°, and Li ４－ｘ Ge １－ｘ P ｘ S ４ Diffraction peaks of a crystal structure similar to that of thio-LISICON Region II type appear, for example, at 2θ=20.2° and 23.6°. Note that these peak positions may vary within a range of ±0.5°.

[0042] The crystal structure of the crystalline sulfide solid electrolyte also includes an argyrodite-type crystal structure. ７ P.S. ６ Crystal structure; Li ７ P.S. ６ The structural skeleton of 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); Li ７－ｘ－２ｙ P.S. ６－ｘ－ｙ Cl ｘ (0.8≦x≦1.7, 0<y≦−0.25x+0.5); Li ７－ｘ P.S. ６－ｘ Ha ｘ (Ha is Cl or Br, and x is preferably 0.2 to 1.8).

[0043] Among the above crystal structures, the crystal structure of the crystalline sulfide solid electrolyte is Li ３ P.S. ４ The crystal structure, the thiolicon region II crystal structure, and the argyrodite crystal structure are preferred.

[0044] The shape of the crystalline sulfide solid electrolyte is not particularly limited, but may be, for example, particulate. The average particle diameter (D ５０ ) is the average particle size (D ５０ ) and the range of 0.01 μm to 500 μm, or 0.1 to 200 μm, for example, can be exemplified.

[0045] In one embodiment, the positive electrode composite contains 40% by mass or more 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-described complex. In one embodiment, the positive electrode composite contains 40 to 90% by mass, 40 to 70% by mass, or 40 to 60% by mass of elemental sulfur and discharge products, calculated as sulfur. Here, the elemental sulfur and discharge products of elemental sulfur are derived from the above-described complex.

[0046] 4. Lithium-ion battery positive electrode and lithium-ion battery A lithium-ion battery positive electrode according to one aspect of the present invention includes the positive electrode mixture according to one aspect of the present invention. The lithium-ion battery positive electrode according to this aspect can impart excellent rate characteristics to the lithium-ion battery.

[0047] A lithium ion battery according to an embodiment of the present invention includes the positive electrode for a lithium ion battery according to an embodiment of the present invention. The lithium ion battery according to this embodiment exhibits excellent rate characteristics.

[0048] The positive electrode composite can be used as the positive electrode layer of a lithium-ion battery. In this case, other components of the lithium-ion battery known in the art can be used, and the negative electrode layer can be selected so that the negative electrode active material does not contain 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." Alternatively, the negative electrode active material contained in the negative electrode layer of the lithium-ion battery can be a "negative electrode active material that supplies lithium ions to the positive electrode."

[0049] The negative electrode of the lithium ion battery is not particularly limited as long as it is one that can be used in ordinary batteries. The negative electrode may be made of a negative electrode mixture that is a mixture of a negative electrode active material and a solid electrolyte.

[0050] As the negative electrode active material, commercially available materials 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 of Si, Sn, Al, Sb, Zn, Bi, etc., SiAl, Sn ５ Cu ６ , Sn ２ Co, Sn ２ Examples include metal alloys such as Fe, amorphous alloys, and plated alloys. There are no particular restrictions on the particle size, but particles with an average particle size of several μm to 80 μm are preferably used.

[0051] The electrolyte layer is not particularly limited, and known electrolytes 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 the one used in the above-mentioned positive electrode composite.

[0052] The method for producing a lithium ion battery is not particularly limited, and examples thereof include a method in which a sheet is formed on a positive electrode current collector, and the sheet is formed with a positive electrode layer made of one or more materials selected from the group consisting of the positive electrode composite according to one embodiment of the present invention and the positive electrode composite according to another embodiment of the present invention, and a solid electrolyte layer is then formed on the sheet, and the sheet on which the negative electrode layer has been formed is laminated on a previously formed negative electrode current collector, followed by pressing.

[0053] 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 all-solid-state lithium-ion batteries according to this embodiment can impart excellent rate characteristics to all-solid-state lithium-ion batteries.

[0054] 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, thereby imparting excellent rate characteristics to the all-solid-state lithium ion battery.

[0055] 7. Method for Manufacturing an All-Solid-State Lithium-Ion Battery A method for manufacturing an all-solid-state lithium-ion battery according to one embodiment of the present invention includes treating activated carbon to reduce oxygen functional groups at a temperature of 500° C. or higher and 1000° C. or lower, thereby imparting excellent rate characteristics to the all-solid-state lithium-ion battery.

[0056] Examples of the present invention will be described below, but the present invention is not limited to these examples.

[0057] (Production Example 1) "Preparation of Activated Carbon 1" Spherical phenolic resin (BEAPS spherical phenolic resin, manufactured by Asahi Organic Chemicals Co., Ltd., particle size 8 μm) was heated in a tubular electric furnace under a nitrogen flow atmosphere (200 mL / min) to 600°C at a rate of 5°C / min, and then maintained for 1 hour to obtain phenolic resin-derived carbon (activated carbon before activation). The obtained phenolic resin-derived carbon and potassium hydroxide in an amount six times the carbon were placed in a Ni crucible, which was then placed in a stainless steel container and heated to 800°C under a nitrogen flow atmosphere (100 mL / min) at a rate of 5°C / min, and maintained for 1 hour to obtain activated carbon (alkali-activated activated carbon) 1. The resulting mixture 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.

[0058] (Production Example 1-1) "Treatment of activated carbon 1 to reduce functional groups in a hydrogen atmosphere" 0.5 g of activated carbon 1 was treated at 600°C for 24 hours with 50 sccm of hydrogen and 200 sccm of argon to reduce the amount of functional groups, thereby obtaining activated carbon 1-1.

[0059] (Production Example 1-2) "Treatment of activated carbon 1 to increase functional groups in an ozone atmosphere" 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 / m ３ for 1 hour at room temperature to provide functional groups, thereby obtaining activated carbon 1-2.

[0060] (Production Example 2) "Preparation of Activated Carbon 2" Spherical phenolic resin (manufactured by Asahi Organic Chemicals Co., Ltd., particle size 17 μm) was heated in a tubular electric furnace under a nitrogen flow atmosphere (200 mL / min) to 600°C at a rate of 5°C / min, and then maintained at this temperature for 1 hour to obtain phenolic resin-derived carbon (activated carbon before activation). The obtained phenolic resin-derived carbon was pressurized to 1.0 MPa (10 atmospheres) in a tubular electric furnace with a carbon dioxide flow rate of 100 to 200 mL / min, heated 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.

[0061] (Production Example 3) "Preparation of Activated Carbon 3" Spherical phenolic resin (manufactured by Asahi Organic Chemicals Co., Ltd., particle size 17 μm) was heated in a tubular electric furnace under a nitrogen flow atmosphere (200 mL / min) to 600°C at a rate of 5°C / min, and then maintained at that temperature for 1 hour to obtain phenolic resin-derived carbon (activated carbon before activation). The obtained phenolic resin-derived carbon was pressurized to 1.0 MPa (10 atmospheres) in a tubular electric furnace with a carbon dioxide flow rate of 100 to 200 mL / min, heated 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.

[0062] (Production Example 4) "Preparation of Activated Carbon 4" Spherical phenolic resin (manufactured by Asahi Organic Chemicals Co., Ltd., particle size 8 μm) was heated in a tubular electric furnace under a nitrogen flow atmosphere (200 mL / min) to 600°C at a rate of 5°C / min, and then maintained at this temperature for 1 hour to obtain phenolic resin-derived carbon (activated carbon before activation). The obtained phenolic resin-derived carbon was pressurized to 1.0 MPa (10 atmospheres) in a tubular electric furnace with a carbon dioxide flow rate of 100 to 200 mL / min, heated 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.

[0063] 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 an SUS tubular container. The mixture was heated in an electric furnace at 150°C for 6 hours and then at 300°C for 2.75 hours to obtain composite powder A of activated carbon and sulfur.

[0064] - Preparation of positive electrode composite "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 having 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) for 40 hours at a rotation speed of 370 rpm to obtain a powder. The obtained powder was heated at 195 ° C. for 3 hours to obtain a solid electrolyte.

[0065] "Preparation of Positive Electrode Composite Powder" 0.2 g of composite powder A and 0.2 g of solid electrolyte were placed in a 45 mL zirconia pot together with 10 zirconia balls with a diameter of 10 mm and sealed. Using a planetary ball mill (manufactured by Fritsch, model number P-7), pulverization was carried out at a rotation speed of 370 rpm for 20 hours to obtain a positive electrode composite powder.

[0066] - Preparation of Lithium-ion Battery (All-Solid State) 100 mg of the solid electrolyte prepared above was placed in a 10 mm diameter Macol cylinder and pressure-molded. The cathode composite powder prepared above was placed on the pressurized surface so that the sulfur content was 3.5 mg, and the battery was again pressure-molded. Lithium titanate ("LT-112" manufactured by Ishihara Sangyo Kaisha), a conductive additive ("Li-100" manufactured by Denka Co., Ltd., powdered acetylene black), and Li were placed on the pressurized surface opposite the cathode composite. ２ S-P ２ S ５ A negative electrode composite (166 mg, also referred to as "lithium titanate (LTO) negative electrode composite") prepared by mixing the lithium ion battery (LiCl-LiBr type solid electrolyte B) and the lithium ion battery (LiCl-LiBr type solid electrolyte B) in a mass ratio of 60:5:35 in a mortar for 5 minutes was added and pressurized, and then lithium foil was further added and pressurized to prepare an all-solid-state battery.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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 activated carbon 1-2 was used instead of activated carbon 1-1.

[0072] 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 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.

[0073]

[0074] The discharge capacity per unit mass of sulfur (capacity at 1 C [mAh / g]) at the 8th cycle (current value during discharge: 5.86 mA) was determined.

[0075] (2) Measurement of the Amount of Functional Groups in Activated Carbon The C1s spectrum of the activated carbon was obtained using XPS, and waveform separation was performed with reference to Patent No. 5966222 to determine the amount of oxygen functional groups (the peak area ratio [%] of oxygen functional groups in the C1s spectrum). 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. Device: VersaProbe II manufactured by ULVAC-PHI, Inc. Excitation X-ray: Al ray, monochromatic 14 kV X-ray diameter / output: 100 μm 100 W Analysis area: 200 μm × 1200 μm Pass energy: 23.5 eV Step energy: 0.1 eV Photoelectron detection angle: 45° Horizontal axis (binding energy): charge neutralization correction with C1s at 284.2 eV

[0076] (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 to prepare the composite (activated carbon of each production example) were determined by measuring a nitrogen adsorption isotherm 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 calculating α ｓ In order to unify the analysis results, α ｓ The analysis of extra-particle and mesopores in the method was performed using αｓ The analysis was carried out in the range of 1 to 2. The results are shown in Table 2.

[0077]

[0078] From Table 2, it can be seen that Examples 1 to 4, which have a small amount of oxygen functional groups, have better battery characteristics (larger capacity) than Comparative Examples 1 and 2.

[0079] Although several embodiments and / or examples of the present invention have been described in detail above, those skilled in the art will readily be able to make numerous modifications to these exemplary embodiments and / or examples without substantially departing from the novel teachings and advantages of the present invention. Accordingly, these numerous modifications are within the scope of the present invention. The contents of all documents cited in this specification and of the applications from which this application claims priority under the Paris Convention are incorporated by reference in their entirety.

Claims

1. A composite comprising: 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; and at least one of elemental sulfur and a discharge product of elemental sulfur.

2. The specific surface area of ​​the activated carbon is 2300 m ２ The composite of claim 1, wherein the molecular weight is 1 / g or more.

3. The composite according to claim 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 claims 1 to 3, wherein the activated carbon has a micropore volume of 1.2 cc / g or more.

5. A method for producing a composite, comprising: combining 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 with at least one of elemental sulfur and a discharge product of elemental sulfur.

6. The specific surface area of ​​the activated carbon is 2300 m ２ The method for producing a composite according to claim 5, wherein the molecular weight of the composite is 1 / g or more.

7. 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.

8. 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.

9. The method for producing a composite according to any one of claims 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 positive electrode composite comprising: 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; and a sulfide solid electrolyte.

11. 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.

12. A positive electrode for a lithium ion battery comprising the positive electrode mixture according to claim 10 or 11.

13. A lithium ion battery comprising the positive electrode mixture according to claim 10 or 11.

14. Activated carbon for use in all-solid-state lithium-ion batteries, in which the peak area ratio of oxygen functional groups in a C1s spectrum obtained by X-ray photoelectron spectroscopy is 15% or less.

15. Use of activated carbon in an all-solid-state lithium-ion battery, the 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.

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.