Composite, method for manufacturing composite, positive electrode composite material, 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

Abstract

A composite body comprising: 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, and at least one of elemental sulfur and a discharge product of elemental sulfur.

Description

Technical Field

[0001] This invention relates to composites, methods for manufacturing composites, positive electrode composite materials, positive electrodes for lithium-ion batteries, lithium-ion batteries, activated carbon for all-solid-state lithium-ion batteries, uses of activated carbon, and methods for manufacturing all-solid-state lithium-ion batteries.

[0002] Specifically, the present invention relates to a composite capable of improving rate performance, a method for manufacturing the composite, a cathode composite material, a cathode for lithium-ion batteries, a lithium-ion battery, activated carbon for all-solid-state lithium-ion batteries, the use of activated carbon, and a method for manufacturing all-solid-state lithium-ion batteries. Background Technology

[0003] The use of sulfur-activated carbon composites in the cathode of all-solid-state lithium-ion batteries has been proposed.

[0004] On the other hand, it has been reported that in liquid lithium-ion batteries, the properties are improved by increasing the oxygen functional groups of the activated carbon used in the sulfur-activated carbon composite (Non-Patent Literature 1).

[0005] Existing technical documents Patent documents Non-patent literature 1: Performance Enhancement of Rechargeable Sulfur Cathode Utilizing Microporous Activated Carbon Composite, Electrochemistry, 2017, 85(10), pp. 671-674 Summary of the Invention The inventors have attempted to further improve the rate performance of all-solid-state lithium-ion batteries using a sulfur-activated carbon composite (hereinafter also referred to as the "composite") in the positive electrode, from the viewpoint of the activated carbon used.

[0006] The prior art, represented by non-patent document 1, has not solved this technical problem.

[0007] One of the objectives of this invention is to provide a composite, a method for manufacturing the composite, a positive electrode composite material, a positive electrode for lithium-ion batteries, a lithium-ion battery, activated carbon for all-solid-state lithium-ion batteries, the uses of activated carbon, and a method for manufacturing all-solid-state lithium-ion batteries, particularly in the case of positive electrodes for all-solid-state lithium-ion batteries, which can improve rate performance.

[0008] The inventors, through in-depth research, discovered that when activated carbon with reduced oxygen functional groups is used as the activated carbon for sulfur-activated carbon composites, the rate characteristics of all-solid-state lithium-ion batteries can be improved, thus completing this invention.

[0009] According to the present invention, the following composites, etc., can be provided.

[0010] 1. A composite comprising: Activated carbon with an oxygen functional group peak area ratio of less than 15% in the C1s spectrum obtained by X-ray photoelectron spectroscopy; and At least one of elemental sulfur and the discharge products of elemental sulfur.

[0011] 2. The composite as described in 1, wherein the specific surface area of ​​the activated carbon is 2300 m². 2 / g or more.

[0012] 3. The composite as described in 1 or 2, wherein the total micropore capacity of the activated carbon is 1.2 cc / g or more.

[0013] 4. The composite as described in any one of 1 to 3, wherein the activated carbon has a micropore capacity of 1.2 cc / g or more.

[0014] 5. A method for manufacturing a composite, comprising: Activated carbon with an oxygen functional group peak area ratio of less than 15% in the C1s spectrum obtained by X-ray photoelectron spectroscopy is combined with at least one of elemental sulfur and the discharge products of elemental sulfur.

[0015] 6. The method for manufacturing the composite as described in 5, wherein the specific surface area of ​​the activated carbon is 2300 m². 2 / g or more.

[0016] 7. The method for manufacturing the composite as described in 5 or 6, wherein the total micropore capacity of the activated carbon is 1.2 cc / g or more.

[0017] 8. The method for manufacturing the composite as described in any one of 5 to 7, wherein the activated carbon has a micropore capacity of 1.2 cc / g or more.

[0018] 9. The method for manufacturing the composite as described in any one of 5 to 8, wherein the activated carbon is subjected to a treatment to reduce oxygen functional groups at a temperature of 500°C to 1000°C.

[0019] 10. A positive electrode composite material, comprising: The composite as described in any one of 1 to 4, or the composite manufactured by the manufacturing method of the composite as described in any one of 5 to 9; and Sulfide solid electrolyte.

[0020] 11. The positive electrode composite material as described in 10, wherein the sulfide solid electrolyte contains at least lithium atoms, phosphorus atoms, sulfur atoms and halogen atoms.

[0021] 12. A positive electrode for a lithium-ion battery, comprising a positive electrode composite material as described in 10 or 11.

[0022] 13. A lithium-ion battery comprising a positive electrode composite material as described in 10 or 11.

[0023] 14. An activated carbon for all-solid-state lithium-ion batteries, wherein the peak area ratio of oxygen functional groups in the C1s spectrum obtained by X-ray photoelectron spectroscopy is less than 15%.

[0024] 15. An application of activated carbon, wherein activated carbon with an oxygen functional group peak area ratio of less than 15% in the C1s spectrum obtained by X-ray photoelectron spectroscopy is used in all-solid-state lithium-ion batteries.

[0025] 16. A method for manufacturing an all-solid-state lithium-ion battery, comprising treating activated carbon at a temperature between 500°C and 1000°C to reduce oxygen functional groups.

[0026] According to the present invention, a composite, a method for manufacturing the composite, a positive electrode composite material, a positive electrode for lithium-ion batteries, a lithium-ion battery, activated carbon for all-solid-state lithium-ion batteries, uses of activated carbon, and a method for manufacturing all-solid-state lithium-ion batteries can be provided, particularly in the case of positive electrodes for all-solid-state lithium-ion batteries, which can improve rate performance. Detailed Implementation

[0027] The following provides a detailed description of the composite, the manufacturing method of the composite, the positive electrode composite material, the positive electrode for lithium-ion batteries, lithium-ion batteries, activated carbon for all-solid-state lithium-ion batteries, the uses of activated carbon, and the manufacturing method of all-solid-state lithium-ion batteries.

[0028] In addition, in this specification, "x~y" refers to a numerical range of "above x and below y". The upper and lower limits of the numerical range can be combined arbitrarily.

[0029] Furthermore, in the various embodiments of the present invention described below, two or more non-contradictory combinations can be made, and embodiments formed by combining two or more embodiments are also embodiments of the present invention.

[0030] 1. Complex The composite involved in one aspect of the present invention comprises: activated carbon with a peak area ratio (hereinafter also referred to as "peak area ratio") of 15% or less in the C1s spectrum obtained by X-ray photoelectron spectroscopy, and... At least one of elemental sulfur and the discharge products of elemental sulfur.

[0031] The composite involved in this solution can improve rate performance, especially in applications such as the cathode of all-solid-state lithium-ion batteries.

[0032] In the composite involved in this scheme, the peak area ratio of activated carbon is less than 15%, that is, the amount of oxygen functional groups is relatively small.

[0033] As mentioned above, it has been reported that in liquid lithium-ion batteries, the more oxygen functional groups in the activated carbon used in the sulfur-activated carbon composite, the better the performance. However, it was unexpectedly found that in the all-solid-state system, the less oxygen functional groups, the better the rate performance.

[0034] Although the reason for this effect may not be clear, it is speculated that it is due to the smaller amount of oxygen functional groups, which inhibits the deterioration of the properties of sulfide solid electrolytes or improves the electronic conductivity of activated carbon.

[0035] (Activated carbon) In one embodiment, the peak area ratio of the activated carbon is 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, but may be, for example, 1.0% or more, 2.0% or more, or 3.0% or more.

[0036] In addition, the peak area ratio is a value determined by the method described in the examples.

[0037] In one embodiment, the specific surface area of ​​the activated carbon is 1500 m². 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 above or 2300m 2 / g or more. There is no specific upper limit; for example, it could be 4000m. 2 / g or less, 3000m 2 / g or less or 2800m 2 / g or less.

[0038] In one embodiment, the specific surface area of ​​the activated carbon is 2300 m².2 / g or more. This allows for a more significant increase in rate capability.

[0039] Furthermore, the specific surface area is a value determined by the method described in the examples.

[0040] In one embodiment, the activated carbon is activated carbon that has undergone treatment to reduce oxygen functional groups at a temperature of 500°C to 1000°C.

[0041] Furthermore, the "treatment to reduce oxygen functional groups" will be discussed in detail later.

[0042] In one embodiment, the activated carbon is pressurized physically activated carbon.

[0043] Furthermore, the topic of "pressure-activated carbon" will be discussed in detail later.

[0044] In one embodiment, the total micropore capacity of the activated carbon is more preferably in the following order: 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. There is no particular limitation on the upper limit of the total micropore capacity; for example, it can be 5 cc / g or less, 4 cc / g or less, or 3 cc / g or less.

[0045] Typical physically activated carbons, such as steam-activated activated carbon, have a total pore volume of less than 1.2 cc / g, which limits their ability to store sulfur effectively. In contrast, activated carbons with a total pore volume of 1.2 cc / g or more can store more sulfur and are therefore preferred.

[0046] In one embodiment, the micropore capacity of the activated carbon is more preferably in the following order: 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. There is no particular limitation on the upper limit of the micropore capacity; for example, it can be 5 cc / g or less, 4 cc / g or less, or 3 cc / g or less.

[0047] The micropore capacity of conventionally activated carbons, such as steam-activated activated carbon, is less than 1.2 cc / g, which limits their ability to store sulfur effectively. In contrast, activated carbons with a micropore capacity of 1.2 cc / g or higher can store more sulfur and are therefore preferred.

[0048] (Elemental sulfur and its discharge products) There are no particular limitations on elemental sulfur (sulfur), but it is preferred to have a purity of 95% by mass or more, more preferably 96% by mass or more, and particularly preferably 97% by mass or more.

[0049] As for the crystal systems of elemental sulfur, examples include α-sulfur (orthorhombic), β-sulfur (monoclinic), γ-sulfur (monoclinic), and amorphous sulfur. These can be used individually or in combination of two or more. Elemental sulfur is melted by heating.

[0050] Elemental sulfur is partially or completely converted into discharge products during the battery reaction. Therefore, in the composite of one embodiment, discharge products of elemental sulfur are present. In the presence of discharge products, the sulfur contained in the composite is the total amount of elemental sulfur and sulfur contained in the discharge products.

[0051] Examples of discharge products of elemental sulfur include Li2S in its fully discharged state and lithium polysulfides such as Li2S2, Li2S4, Li2S6, and Li2S8 in its intermediate stage.

[0052] In one embodiment, in the composite, some or all of the elemental sulfur is attached (impregnated) within the pores of the activated carbon. Furthermore, elemental sulfur not impregnated within the pores exists in a manner that coats part or all of the activated carbon. Whether sulfur is impregnated within the pores of the activated carbon can be confirmed by analyzing the particle cross-section of the activated carbon using elemental mapping analytical methods such as SEM-EDS or TEM-EDX, and by evaluating the overlap between elements originating from the activated carbon and sulfur elements.

[0053] In one embodiment, since the composite contains a high amount of elemental sulfur, which is also present outside the pores of the activated carbon, the composite can be a granular mass, but can be pulverized by mechanical crushing.

[0054] In one embodiment, the composite comprises, relative to 100 parts by mass of activated carbon, 150–600 parts by mass, 200–550 parts by mass, or 220–500 parts by mass (calculated as sulfur) of elemental sulfur and discharge products of elemental sulfur. If the amount is 600 parts by mass or less, the sulfur in the activated carbon can be uniformly imparted with conductivity, and higher battery performance can be expected when the composite material is manufactured. By having 150 parts by mass or more, sufficient sulfur content is ensured, and electrode materials with higher energy density can be obtained.

[0055] 2. Manufacturing method of the composite One aspect of the present invention relates to a method for manufacturing a composite, comprising: combining activated carbon, wherein the peak area ratio of oxygen functional groups in the C1s spectrum obtained by X-ray photoelectron spectroscopy is less than 15%, with at least one of elemental sulfur and the discharge products of elemental sulfur.

[0056] Thus, the composite involved in one aspect of the present invention can be obtained.

[0057] In this embodiment, the activated carbon used for composite processing has a peak area ratio of oxygen functional groups of 15% or less in the C1s spectrum obtained by X-ray photoelectron spectroscopy. The following methods, described as the first and second embodiments, can be used as a method for manufacturing such activated carbon.

[0058] (First Embodiment) In the first embodiment, the raw activated carbon is treated to reduce oxygen functional groups. This allows the production of activated carbon with an oxygen functional group peak area ratio of 15% or less in the C1s spectrum obtained by X-ray photoelectron spectroscopy.

[0059] There are no particular limitations on the activated carbon used as a raw material. Examples include: activated carbon derived from phenolic resin obtained by burning and carbonizing spherical phenolic resin; carbon derived from plants such as wood 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.

[0060] Activated carbon derived from phenolic resins has a high char residue, and since it is a synthetic resin raw material, structural control is highly desirable. Furthermore, plant-derived carbon compounds are expected to exhibit hierarchical structures derived from plant sources; additionally, from the perspective of decarbonization, this is desirable because plants absorb carbon dioxide from the air during growth. Moreover, carbon derived from petroleum bitumen or coal tar pitch has the advantage of being readily available in large quantities at low cost.

[0061] For the raw material activated carbon, activation treatments such as alkali activation treatment using alkali (such as potassium hydroxide) can also be performed. As an alkali activation treatment, for example, a method can be used to keep activated carbon and potassium hydroxide in a nitrogen atmosphere at a temperature of 500°C to 1000°C for 10 to 120 minutes.

[0062] Activated carbon with a peak area ratio exceeding 15% can be used as a raw material.

[0063] Alternatively, activated carbon with a peak area ratio of less than 15% can be used as the raw material. In this case, the peak area ratio (oxygen functional group content) can be further reduced by reducing the amount of oxygen functional groups.

[0064] As a treatment to reduce the amount of oxygen functional groups, the raw activated carbon can be processed (heat treatment) at temperatures above 500°C and below 1000°C.

[0065] The atmosphere during processing is preferably free of oxygen and water vapor.

[0066] In addition, the atmosphere used during processing preferably includes inert gases such as nitrogen (N2) and argon.

[0067] Furthermore, the processing atmosphere preferably contains hydrogen (H2). Because the processing atmosphere contains hydrogen, the free radicals on the carbon surface after the functional groups have been removed can be capped with hydrogen, thus preventing the re-oxidation and generation of oxygen functional groups after exposure to the atmosphere.

[0068] When the atmosphere during processing contains hydrogen, the concentration of hydrogen is, for example, 10 to 100% by volume. The remainder is preferably an inert gas such as nitrogen or argon.

[0069] The activated carbon used as raw material is preferably supplied separately for the treatment of reducing the amount of oxygen functional groups. Here, "separately" means not coexisting with the alkali (such as potassium hydroxide) used in the alkaline activation treatment. Of course, the gases that form the above atmosphere can coexist.

[0070] 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. There is no particular upper limit; for example, it can be less than 120 hours, less than 60 hours, less than 48 hours, or less than 36 hours.

[0071] (Second Implementation) In the second embodiment, the activated carbon is physically activated under pressure. This allows the acquisition of activated carbon with a peak area ratio of 15% or less (pressurized physically activated activated carbon).

[0072] There are no particular limitations on the activated carbon used for pressurized physical activation treatment; for example, the aforementioned activated carbon used as raw material activated carbon can be used.

[0073] Gases used for pressurized physical activation include carbon dioxide, water vapor, oxygen, and air. Using carbon dioxide as the gas for pressurized physical activation results in a mild activation effect and makes it easy to control the degree of activation.

[0074] The concentration of carbon dioxide in the gas is, for example, 50 to 100 by volume.

[0075] In one embodiment, pressurized physical activation is performed at a pressure of 2 atmospheres or more.

[0076] In one embodiment, pressurized physical activation is performed at an absolute pressure of 2 to 100 atmospheres, 3 to 10 atmospheres, or 5 to 9 atmospheres.

[0077] In one embodiment, the pressurized physical activation treatment time using carbon dioxide is more than 0 minutes and less than 99 hours, more than 1 minute and less than 24 hours, or more than 5 minutes and less than 8 hours.

[0078] The temperature for pressurized physical activation treatment using carbon dioxide can be appropriately set according to the pressure, etc., but it is preferably 600°C or higher, more preferably 700°C or higher. Furthermore, it is preferably 1200°C or lower, more preferably 1100°C or lower.

[0079] For details regarding the raw material activated carbon (peak area ratio, specific surface area, total pore volume, and micropore volume, etc.), please appropriately cite the description of activated carbon in the composite.

[0080] (Complex) The activated carbon (raw material activated carbon) with a peak area ratio of less than 15% obtained as described above is compounded with at least one of elemental sulfur and the discharge products of elemental sulfur.

[0081] Here, "composite" means attaching at least one of elemental sulfur and its discharge products to the surface of activated carbon (both the inner and outer surfaces of the pores). This can be achieved by coating the surface of activated carbon with at least one of elemental sulfur and its discharge products.

[0082] There are no particular limitations on the method of compounding. For example, a method can be listed as mixing raw activated carbon with at least one of elemental sulfur and the discharge products of elemental sulfur and then heating it.

[0083] The heating temperature is not particularly limited, but can be, for example, 130–445°C, 140–400°C, or 150–350°C. If the heating temperature is above 130°C, it exceeds the melting point of elemental sulfur (115°C), thus the sulfur melts, and impregnation of activated carbon can be expected. The upper limit of the heating temperature is preferably below or below the boiling point of elemental sulfur (445°C). In particular, since lithium polysulfides or lithium sulfides, which are discharge products of elemental sulfur, have high melting points, the temperature can be further increased beyond 445°C.

[0084] There is no particular limitation on the heating time, for example, it can be 0.1 to 99 hours, 1 to 24 hours or 2 to 8 hours.

[0085] 3. Positive electrode composite material One aspect of the present invention relates to a cathode composite material comprising: the composite material according to one aspect of the present invention, or a composite material manufactured by the manufacturing method of the composite material according to one aspect of the present invention; and a sulfide solid electrolyte. This enables the lithium-ion battery to possess excellent rate performance.

[0086] (Sulfide solid electrolyte) A sulfide solid electrolyte is a solid electrolyte that contains at least sulfur atoms and exhibits ionic conductivity caused by the contained metal atoms. In addition to sulfur atoms, it preferably contains lithium atoms and phosphorus atoms, and more preferably contains lithium atoms, phosphorus atoms and halogen atoms. It is a solid electrolyte having ionic conductivity caused by lithium atoms.

[0087] In one embodiment, the solid electrolyte contains at least lithium atoms, phosphorus atoms, sulfur atoms and halogen atoms.

[0088] In one embodiment, the solid electrolyte comprises lithium atoms, phosphorus atoms, sulfur atoms, bromine atoms, and iodine atoms.

[0089] As a sulfide solid electrolyte, it can be either an amorphous sulfide solid electrolyte or a crystalline sulfide solid electrolyte.

[0090] (Amorphous sulfide solid electrolyte) As an amorphous sulfide solid electrolyte, any electrolyte that contains at least sulfur atoms and exhibits ionic conductivity caused by the contained metal atoms can be used without particular limitation. Representative amorphous sulfide solid electrolytes include, for example, solid electrolytes containing sulfur atoms, lithium atoms, and phosphorus atoms such as Li2S-P2S5 composed of lithium sulfide and phosphorus sulfide; solid electrolytes composed of lithium sulfide, phosphorus sulfide, and lithium halide such as Li2S-P2S5-LiI, Li2S-P2S5-LiCl, Li2S-P2S5-LiBr, and Li2S-P2S5-LiI-LiBr; and solid electrolytes that also contain other elements such as oxygen and silicon, such as Li2S-P2S5-Li2O-LiI and Li2S-SiS2-P2S5-LiI. From the viewpoint of obtaining higher ionic conductivity, solid electrolytes composed of lithium sulfide, phosphorus sulfide and lithium halide, such as Li2S-P2S5-LiI, Li2S-P2S5-LiCl, Li2S-P2S5-LiBr and Li2S-P2S5-LiI-LiBr, are preferred.

[0091] The types of elements constituting amorphous sulfide solid electrolytes can be identified, for example, by using an ICP-based luminescence spectrophotometer.

[0092] When the amorphous sulfide solid electrolyte has at least Li2S-P2S5, from the viewpoint of high chemical stability and higher ionic conductivity, the molar ratio of Li2S to P2S5 is preferably 30-85:15-70, more preferably 40-80:20-60, and even more preferably 45-78:22-55.

[0093] In the case of an amorphous sulfide solid electrolyte, such as Li₂S-P₂S₅-LiI-LiBr, the total content of lithium sulfide and phosphorus pentasulfide is preferably 30-95 mol%, more preferably 35-90 mol%, and even more preferably 40-85 mol%. Furthermore, the ratio of lithium bromide to the total content of lithium bromide and lithium iodide is preferably 1-99 mol%, more preferably 20-90 mol%, even more preferably 40-80 mol%, and particularly preferably 50-70 mol%.

[0094] Furthermore, there are no particular limitations on the shape of the amorphous sulfide solid electrolyte; for example, particulate form can be cited. The average particle size (D) of the particulate amorphous sulfide solid electrolyte... 50 For example, it can exemplify the range of 0.01μm to 500μm and 0.1 to 200μm.

[0095] In this specification, the average particle size (D) 50 The volume distribution is the particle size at which 50% of the total particle size is accumulated from the smallest particle when plotting the cumulative particle size distribution curve. For example, the average particle size can be measured using a laser diffraction / scattering particle size distribution measurement device.

[0096] (Crystall sulfide solid electrolyte) As a crystalline sulfide solid electrolyte, for example, it can be a so-called glass ceramic obtained by heating the above-mentioned amorphous sulfide solid electrolyte to above the crystallization temperature, and a sulfide solid electrolyte having the following crystal structure can be used.

[0097] Crystal structures that can be possessed by crystalline sulfide solid electrolytes containing lithium, sulfur, and phosphorus atoms include Li3PS4, Li4P2S6, Li7PS6, and Li7P3S6. 11 Crystal structures, crystal structures with peaks around 2θ = 20.2° and around 23.6° (e.g., Japanese Patent Application Publication No. 2013-16423), etc.

[0098] Furthermore, as a crystalline sulfide solid electrolyte containing lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms, the aforementioned Li... 4-x Ge 1-x P x S4 type sulfide crystalline lithium superionic conductor thio-LISICON Region II crystal structure, and Li 4-x Ge 1-x P x Similar crystal structures to the S4 type sulfide crystalline lithium superion conductor thio-LISICON Region II type.

[0099] In the X-ray diffraction measurement using CuKα rays, the diffraction peaks of the Li3PS4 crystal structure appear near 2θ = 17.5°, 18.3°, 26.1°, 27.3°, 30.0°, for example. The diffraction peaks of the Li4P2S6 crystal structure appear near 2θ = 16.9°, 27.1°, 32.5°, for example. The diffraction peaks of the Li7PS6 crystal structure appear near 2θ = 15.3°, 25.2°, 29.6°, 31.0°, for example, and the diffraction peaks of the Li7P3S 11 crystal structure appear near 2θ = 17.8°, 18.5°, 19.7°, 21.8°, 23.7°, 25.9°, 29.6°, 30.0°, for example, and those of Li 4-x Ge 1-x P x The diffraction peaks of the thio-LISICON Region II type crystal structure of the lithium superionic conductor of the LiGePS4 type appear near 2θ = 20.1°, 23.9°, 29.5°, for example, similar to those of the Li 4-x Ge 1-x P x The diffraction peaks of the thio-LISICON Region II type crystal structure similar to that of the LiGePS4 type appear near 2θ = 20.2°, 23.6°, for example. Additionally, these peak positions can fluctuate within a range of ±0.5°.

[0100] Furthermore, as the crystal structure of the crystalline sulfide solid electrolyte, the argyrodite type crystal structure can also be cited. As the argyrodite type crystal structure, for example, the Li7PS6 crystal structure can be cited; the crystal structures represented by the composition formula Li 7-x P 1-y Si y S6 and Li 7+x P 1-y Si y S6 (where x is -0.6 to 0.6 and y is 0.1 to 0.6); the crystal structures represented by Li 7-x-2y PS 6-x-y Cl x (0.8 ≤ x ≤ 1.7, 0 < y ≤ -0.25x + 0.5); the crystal structures represented by Li 7-x PS 6-x Ha x (where Ha is Cl or Br and x is preferably 0.2 to 1.8).

[0101] Among the above crystal structures, the preferred crystal structures for crystalline sulfide solid electrolytes are the Li3PS4 crystal structure, the sulfide crystalline lithium superion conductor region II crystal structure, and the sulfosilver germanite type crystal structure.

[0102] The shape of the crystalline sulfide solid electrolyte is not particularly limited; for example, particulate form can be cited. The average particle size (D) of the particulate crystalline sulfide solid electrolyte... 50 ) and the average particle size (D) of the previously described amorphous sulfide solid electrolyte 50 Similarly, for example, it is possible to exemplify the range of 0.01μm to 500μm and 0.1 to 200μm.

[0103] In one embodiment, the cathode composite material comprises at least 40% by mass of elemental sulfur and its discharge products. Here, the elemental sulfur and its discharge products are derived from the composite.

[0104] In one embodiment, the cathode composite material comprises 40–90% by mass, 40–70% by mass, or 40–60% by mass of elemental sulfur and its discharge products, calculated in terms of sulfur content. Here, the elemental sulfur and its discharge products originate from the aforementioned composite.

[0105] 4. Positive electrode for lithium-ion batteries and lithium-ion batteries The positive electrode for lithium-ion batteries according to one aspect of the present invention comprises the positive electrode composite material according to one aspect of the present invention.

[0106] The positive electrode for lithium-ion batteries described in this solution can impart excellent rate performance to lithium-ion batteries.

[0107] One aspect of the present invention relates to a lithium-ion battery comprising a positive electrode for a lithium-ion battery as described in one aspect of the present invention.

[0108] The lithium-ion battery involved in this solution can achieve excellent rate performance.

[0109] Positive electrode composite materials can be used as the positive electrode layer of lithium-ion batteries. In this case, other components of the lithium-ion battery can use those known in the art, and a negative electrode layer whose negative electrode active material does not contain lithium ions can be selected.

[0110] Alternatively, the negative electrode active material contained in the negative electrode layer of a lithium-ion battery can be defined as "a negative electrode active material containing lithium ions". Alternatively, the negative electrode active material contained in the negative electrode layer of a lithium-ion battery can also be "a negative electrode active material that supplies lithium ions to the positive electrode".

[0111] There are no particular restrictions on the negative electrode of a lithium-ion battery, as long as it is a negative electrode that can be used in conventional batteries. The negative electrode can also be made of a composite material made by mixing negative electrode active material with a solid electrolyte.

[0112] Commercially available materials can be used as the negative electrode active material. For example, carbon materials, Sn metal, In metal, Si metal, Li metal, and alloys of these metals can be used. Specifically, examples include natural graphite or various types of graphite, lithium titanate, metal powders such as Si, Sn, Al, Sb, Zn, and Bi, metal alloys such as SiAl, Sn5Cu6, Sn2Co, and Sn2Fe, other amorphous alloys, or coated alloys. There are no particular restrictions on particle size; materials with an average particle size of several μm to 80 μm can be appropriately used.

[0113] There are no particular limitations on the electrolyte layer, and known electrolyte layers can be used. For example, oxide solid electrolytes, sulfide solid electrolytes, and polymer electrolytes are preferred, and from the viewpoint of ionic conductivity, sulfide solid electrolytes are more preferred. This sulfide solid electrolyte is preferably an electrolyte used in the above-mentioned positive electrode composite material.

[0114] There are no particular limitations on the manufacturing method of lithium-ion batteries. For example, the following methods can be used: forming a sheet by forming a positive electrode layer on a positive current collector, forming a solid electrolyte layer on the sheet, stacking a sheet with a negative electrode layer formed on a negative current collector beforehand, and applying pressure, wherein the positive electrode layer is composed of one or more of the positive electrode composite materials selected from the group consisting of positive electrode composite materials according to one aspect of the present invention and positive electrode composite materials according to other aspects of the present invention.

[0115] 5. Activated carbon for all-solid-state lithium-ion batteries The activated carbon for all-solid-state lithium-ion batteries involved in one aspect of the present invention has a peak area ratio of oxygen functional groups in the C1s spectrum obtained by X-ray photoelectron spectroscopy of less than 15%.

[0116] The activated carbon used in this solution for all-solid-state lithium-ion batteries can impart excellent rate performance to all-solid-state lithium-ion batteries.

[0117] 6. Uses of activated carbon One application of the activated carbon involved in this invention is to use activated carbon with an oxygen functional group peak area ratio of less than 15% in the C1s spectrum obtained by X-ray photoelectron spectroscopy in all-solid-state lithium-ion batteries.

[0118] This allows all-solid-state lithium-ion batteries to possess excellent rate performance.

[0119] 7. Manufacturing method of all-solid-state lithium-ion batteries One aspect of the present invention relates to a method for manufacturing an all-solid-state lithium-ion battery, which includes treating activated carbon at a temperature between 500°C and 1000°C to reduce oxygen functional groups.

[0120] This allows all-solid-state lithium-ion batteries to possess excellent rate performance.

[0121] [Example] The following describes embodiments of the present invention, but the present invention is not limited to these embodiments.

[0122] (Manufacturing Example 1) "The generation of activated carbon 1" Spherical phenolic resin (spherical phenolic resin BEAPS, manufactured by Asahi Organic Materials Co., Ltd., particle size 8 μm) was carbonized in a tube furnace under a nitrogen atmosphere (200 mL / min) at a temperature of 5 °C / min to 600 °C, and held for 1 hour to obtain carbon derived from phenolic resin (activated carbon before activation).

[0123] The carbon derived from phenolic resin and six times the amount of potassium hydroxide were placed in a Ni crucible, which was then placed in a stainless steel container and heated to 800°C at 5°C / min under a nitrogen atmosphere (100 mL / min) and held for 1 hour for activation. After neutralization with hydrochloric acid, the carbon was washed with water until the pH became 7 and then dried to obtain activated carbon (alkali-activated activated carbon) 1.

[0124] (Manufacturing Example 1-1) "Functional group reduction treatment of activated carbon 1 under hydrogen atmosphere" The amount of functional groups was reduced by treating 0.5g of activated carbon 1 at 600℃ for 24 hours under hydrogen at 50sccm and argon at 200sccm, thus obtaining activated carbon 1-1.

[0125] (Manufacturing Examples 1-2) "Functional group enhancement treatment of activated carbon 1 under ozone atmosphere" By using NZR-60MF manufactured by Roki Techno Co., Ltd., with an oxygen supply rate set at 1L / min and an ozone concentration of 20g / m³, 3 At room temperature, 0.4 g of activated carbon 1 was treated for 1 hour to impart functional groups, resulting in activated carbon 1-2.

[0126] (Manufacturing Example 2) "The generation of activated carbon 2" Spherical phenolic resin (manufactured by Asahi Organic Materials Co., Ltd., particle size 17μm) was carbonized in a tube furnace at a temperature of 5℃ / min under a nitrogen atmosphere (200mL / min) to 600℃, and held for 1 hour to obtain carbon derived from phenolic resin (activated carbon before activation).

[0127] The carbon derived from phenolic resin was pressurized to 1.0 MPa (10 atmospheres) in a tube furnace at a carbon dioxide flow rate of 100-200 mL / min, heated to 1000℃ at a rate of 5℃ / min, and activated for 30 minutes to obtain activated carbon (pressurized carbon dioxide activated activated carbon) 2.

[0128] (Manufacturing Example 3) "The generation of activated carbon 3" Spherical phenolic resin (manufactured by Asahi Organic Materials Co., Ltd., particle size 17μm) was carbonized in a tube furnace at a temperature of 5℃ / min under a nitrogen atmosphere (200mL / min) to 600℃, and held for 1 hour to obtain carbon derived from phenolic resin (activated carbon before activation).

[0129] The carbon derived from phenolic resin was pressurized to 1.0 MPa (10 atmospheres) in a tube furnace at a carbon dioxide flow rate of 100-200 mL / min, heated to 1000℃ at a rate of 5℃ / min, and activated for 1 hour to obtain activated carbon (pressurized carbon dioxide activated activated carbon) 3.

[0130] (Manufacturing Example 4) "The generation of activated carbon 4" Spherical phenolic resin (manufactured by Asahi Organic Materials Co., Ltd., particle size 8 μm) was carbonized in a tube furnace at a temperature of 5 °C / min under a nitrogen atmosphere (200 mL / min) and held for 1 hour to obtain carbon derived from phenolic resin (activated carbon before activation).

[0131] The carbon derived from phenolic resin was pressurized to 1.0 MPa (10 atmospheres) in a tube furnace at a carbon dioxide flow rate of 100-200 mL / min, heated to 1000℃ at a rate of 5℃ / min, and activated for 20 minutes to obtain activated carbon (pressurized carbon dioxide activated activated carbon) 4.

[0132] (Example 1) • Fabrication of composite powders (composite materials) Preparation of Composite Powder A Activated carbon 1-1 and sulfur (S) were placed in a glass bottle at a weight ratio of 1:5 and sealed inside a SUS tube 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 a composite powder A of activated carbon and sulfur.

[0133] • Fabrication of cathode composite materials "Preparation of Solid Electrolytes" 0.4127 g of lithium sulfide, 0.6655 g of phosphorus pentasulfide, 0.2137 g of lithium iodide, 0.2080 g of lithium bromide, and 10 zirconium oxide balls with a diameter of 10 mm were placed into a 45 mL zirconium oxide container and sealed. The mixture was mechanically ground at 370 rpm for 40 hours using a planetary ball mill (Fritsch, model P-7) to obtain a powder. The resulting powder was then heated at 195 °C for 3 hours to obtain a solid electrolyte.

[0134] "Preparation of cathode composite material powder" 0.2 g of composite powder A and 0.2 g of solid electrolyte, along with 10 zirconia balls with a diameter of 10 mm, were placed into a 45 mL zirconia container and sealed. The mixture was then pulverized using a planetary ball mill (Fritsch, model P-7) at 370 rpm for 20 hours to obtain the cathode composite powder.

[0135] • Manufacturing of lithium-ion batteries (all solid-state) In a Macor cylinder with a diameter of 10 mm, 100 mg of the solid electrolyte prepared above was added and pressurized. On the pressurized surface, the positive electrode composite powder prepared above was added to achieve a sulfur content of 3.5 mg, and it was pressurized again. On the pressurized surface opposite to the positive electrode composite, 166 mg of negative electrode composite (also known as "LTO (lithium titanate) negative electrode composite") was added. After pressurization, lithium foil was added and pressurized again to manufacture an all-solid-state battery. The negative electrode composite was obtained by mixing lithium titanate (Ishihara Sangyo's "LT-112"), conductive additives (Nippon Denka Co., Ltd.'s "Li-100", powdered acetylene black), and Li2S-P2S5-LiCl-LiBr type solid electrolyte B in a mortar and pestle at a mass ratio of 60:5:35 for 5 minutes.

[0136] (Example 2) Except that activated carbon 2 was used instead of activated carbon 1-1, composite powder, positive electrode composite material and lithium-ion battery were manufactured in the same manner as in Example 1.

[0137] (Example 3) Except that activated carbon 3 was used instead of activated carbon 1-1, composite powder, positive electrode composite material and lithium-ion battery were manufactured in the same manner as in Example 1.

[0138] (Example 4) Except for using activated carbon 4 instead of activated carbon 1-1, composite powder, positive electrode composite material and lithium-ion battery were manufactured in the same manner as in Example 1.

[0139] (Comparative Example 1) A composite powder, a positive electrode composite material, 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.

[0140] (Comparative Example 2) A composite powder, a positive electrode composite material, 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.

[0141] Test method and evaluation method (1) Evaluation of battery characteristics A constant current charge-discharge test was performed on the all-solid-state batteries obtained in the examples and comparative examples. The cut-off potential for the constant current test was set to -0.4 to +1.3 V vs. Li-LTO, and the current value was set to the conditions shown in Table 1 below.

[0142] [Table 1]

[0143] The discharge capacity per unit mass of sulfur (capacity at 1 C [mAh / g]) in the 8th cycle (discharge current value: 5.86 mA) was determined.

[0144] (2) Determination of the amount of functional groups of activated carbon The C1s spectrum of the activated carbon was obtained using XPS, and the waveform was separated by referring to Japanese Patent No. 5966222 to determine the amount of oxygen functional groups (peak area ratio [%] of oxygen functional groups in the C1s spectrum). Here, the XPS measurement apparatus and measurement conditions are as described below.

[0145] [XPS measurement apparatus and measurement conditions] Measurement was performed using a transfer container to prevent the sample from being exposed to the atmosphere.

[0146] Apparatus: VersaProbeII manufactured by ULVAC-PHI Excitation X-ray: Al line, monochromatic 14 kV X-ray diameter, output power: 100 μm 100 W Analysis area: 200 μm × 1200 μm Channel energy: 23.5 eV Energy step: 0.1 eV Photoelectron detection angle: 45° Horizontal axis (binding energy): Charge neutralization correction with C1s set to 284.2 eV (3) Determination of the specific surface area, micropore volume, and total pore volume of activated carbon The specific surface area, micropore capacity, and total micropore capacity of the activated carbon used to prepare the composites (activated carbon in each manufacturing example) were determined using the Quantachrome Autosorb-3 micropore distribution measuring apparatus or the Anton Paar Nova apparatus. Nitrogen adsorption isotherms were measured, and α-type micropores were used. s The method was analyzed.

[0147] In addition, to unify the analysis results, α s The analysis of external particles and mesopores in the method, with all samples in α s The parsing was performed in the range of 1 to 2.

[0148] The results are shown in Table 2.

[0149] [Table 2]

[0150] As shown in Table 2, Examples 1-4, which have less oxygen functional groups, have superior battery characteristics (larger capacity) compared to Comparative Examples 1 and 2.

[0151] The foregoing has described several embodiments and / or examples of the present invention in detail. However, those skilled in the art can readily make numerous modifications to these illustrated embodiments and / or examples without substantially departing from the new teachings and effects of the present invention. Therefore, these numerous modifications are also included within the scope of the present invention.

[0152] The entire contents of the documents described in this specification and the applications based on the Paris Convention priority are hereby cited.

Claims

1. A composite, characterized in that, Include: Activated carbon with an oxygen functional group peak area ratio of less than 15% in the C1s spectrum obtained by X-ray photoelectron spectroscopy; and At least one of elemental sulfur and the discharge products of elemental sulfur.

2. The composite as described in claim 1, characterized in that, The specific surface area of ​​the activated carbon is 2300 m². 2 / g or more.

3. The composite as described in claim 1 or 2, characterized in that, The total micropore capacity of the activated carbon is above 1.2 cc / g.

4. The composite as described in any one of claims 1 to 3, characterized in that, The activated carbon has a micropore capacity of 1.2 cc / g or higher.

5. A method for manufacturing a composite, characterized in that, include: Activated carbon with an oxygen functional group peak area ratio of less than 15% in the C1s spectrum obtained by X-ray photoelectron spectroscopy is combined with at least one of elemental sulfur and the discharge products of elemental sulfur.

6. The method for manufacturing the composite as described in claim 5, characterized in that, The specific surface area of ​​the activated carbon is 2300 m². 2 / g or more.

7. The method for manufacturing the composite as described in claim 5 or 6, characterized in that, The total micropore capacity of the activated carbon is above 1.2 cc / g.

8. The method for manufacturing the composite according to any one of claims 5 to 7, characterized in that, The activated carbon has a micropore capacity of 1.2 cc / g or higher.

9. The method for manufacturing the composite according to any one of claims 5 to 8, characterized in that, The activated carbon was subjected to a treatment at a temperature between 500°C and 1000°C to reduce oxygen functional groups.

10. A positive electrode composite material, characterized in that, Include: The composite as described in any one of claims 1 to 4, or the composite manufactured by the method for manufacturing the composite as described in any one of claims 5 to 9; and Sulfide solid electrolyte.

11. The positive electrode composite material as described in claim 10, characterized in that, 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, characterized in that, It includes the positive electrode composite material as described in claim 10 or 11.

13. A lithium-ion battery, characterized in that, It includes the positive electrode composite material as described in claim 10 or 11.

14. An activated carbon for all-solid-state lithium-ion batteries, characterized in that, The peak area ratio of oxygen functional groups in the C1s spectrum obtained by X-ray photoelectron spectroscopy is less than 15%.

15. An application of activated carbon, characterized in that, Activated carbon with an oxygen functional group peak area ratio of less than 15% in the C1s spectrum obtained by X-ray photoelectron spectroscopy is used in all-solid-state lithium-ion batteries.

16. A method for manufacturing an all-solid-state lithium-ion battery, characterized in that, This includes treating activated carbon at temperatures between 500°C and 1000°C to reduce oxygen functional groups.

Images