Positive electrode mixture

Abstract

A positive electrode mixture containing: a sulfur-based active material; a porous carbon material; at least one of an elemental-phosphorus-containing ion conductor and a variant of said ion conductor; and a solid electrolyte, wherein at least one of formulas (1) and (2) is satisfied in the P2p spectrum of a surface elemental analysis by X-ray photoelectron spectroscopy.　Formula (1): IA / IB>0.50, formula (2): IC / IB>1.20 (In the formulas, IA is the signal strength at a position A where the binding energy is around 135.4 eV, IB is the signal strength at a position B where the binding energy is around 134.25 eV, and IC is the signal strength at a position C where the binding energy is around 133.0 eV.)

Description

Positive electrode mixture

[0001] The present invention relates to a positive electrode mixture and a method for producing the same.

[0002] Lithium-ion batteries require high battery capacity. To improve battery capacity, the use of sulfur in the cathode has been investigated due to its large theoretical capacity. However, sulfur has low lithium ion and electronic conductivity, so when sulfur is used in the cathode, it is necessary to ensure the lithium ion and electronic conductivity within the cathode.

[0003] To address the above-mentioned issues, a cathode composite has been investigated in which sulfur, a carbon material, diphosphorus pentasulfide, a solid electrolyte, etc. are mechanically mixed in a planetary ball mill to form a composite (see, for example, Patent Documents 1 and 2). Also, a cathode composite has been investigated in which sulfur, a carbon material having pores, and a solid electrolyte are combined, with the solid electrolyte being placed in the pores of the carbon material from a solution state (see, for example, Patent Documents 3 and 4).

[0004] Patent No. 7156157 Patent No. 6061139 Patent No. 7283657 International Publication No. 2023 / 187466

[0005] There is a demand for further improvement in charge-discharge characteristics compared to conventional techniques. Conventional mechanical mixing (mechanical milling) methods, such as those described in Patent Documents 1 and 2, result in insufficient interface formation between the sulfur and carbon material in the resulting composite and the solid electrolyte, diphosphorus pentasulfide, etc., limiting the formation of ion conduction paths between the sulfur and the carbon material. Techniques for precipitating a solid electrolyte from a solution, such as those described in Patent Documents 3 and 4, result in insufficient interface formation between the sulfur and carbon material in the resulting composite and the solid electrolyte, limiting the formation of ion conduction paths between the sulfur and the carbon material. One object of the present invention is to provide a positive electrode composite that can improve the charge-discharge characteristics of lithium-ion batteries.

[0006] According to the present invention, the following positive electrode composite and the like are provided. 1. A positive electrode composite comprising a sulfur-based active material, a carbon material having micropores, at least one of an ionic conductor containing elemental phosphorus and a modified form of the ionic conductor, and a solid electrolyte, wherein the P2p spectrum in surface elemental analysis by X-ray photoelectron spectroscopy satisfies at least one of the following formulas (1) and (2): Ａ / I Ｂ >0.50 (1) I Ｃ / I Ｂ >1.20 (2) (wherein, I Ａ is the signal intensity at position A where the binding energy is around 135.4 eV, I Ｂ is the signal intensity at position B where the binding energy is around 134.25 eV, I Ｃ is the signal intensity at position C where the binding energy is around 133.0 eV.) 2. Ｃ / I Ｂ 2. The positive electrode mixture according to 1, wherein the ratio of change in the elemental ratio C / P of carbon to phosphorus before and after Ar sputtering treatment is 0.550 or more, as determined by surface elemental analysis using X-ray photoelectron spectroscopy. 3. The positive electrode mixture according to 1 or 2, wherein the ratio of change in the elemental ratio C / P is 0.600 or more. 4. The positive electrode mixture according to 3, wherein the ratio of change in the elemental ratio C / P is 0.600 or more. 5. A solid ３１ In the P-NMR measurement, P ２ S ６ ４－ Peak and PS ３ － 5. The positive electrode mixture according to any one of 1 to 4, wherein the sum of the areas of the peaks of ３１ In the P-NMR measurement, P ２ S ５is 25% or less of the total. 7. The cathode mixture according to any one of 1 to 5, wherein the melting point of the ion conductor is 130°C to 450°C. 8. The cathode mixture according to any one of 1 to 7, wherein the ion conductor comprises a lithium ion conductive material or a precursor thereof containing elemental phosphorus and one or more elements selected from lithium, boron, sulfur, and oxygen. 9. The cathode mixture according to any one of 1 to 8, wherein the ion conductor comprises phosphorus sulfide. 10. The cathode mixture according to any one of 1 to 9, wherein the ion conductor comprises diphosphorus pentasulfide. 11. The cathode mixture according to any one of 1 to 10, wherein the sulfur-based active material comprises elemental sulfur. 12. The cathode mixture according to any one of 1 to 11, wherein the mass ratio of the sum of the sulfur-based active material, the ion conductor containing elemental phosphorus, and a modified product of the ion conductor to the carbon material is less than 5.00. 13. 14. A method for producing a cathode composite, comprising mixing at least one of a composite and a mixture of a sulfur-based active material and a carbon material having pores with a molten ion conductor to prepare a cathode composite precursor, and mixing and grinding the cathode composite precursor and a crystalline solid electrolyte under conditions that do not cause the crystallinity of the solid electrolyte to be lost. 15. The method for producing a cathode composite according to 13, wherein the composite of a sulfur-based active material and a carbon material having pores is mixed with the molten ion conductor. 16. The method for producing a cathode composite according to any one of 13 to 15, wherein the ion conductor comprises a lithium ion conductive material or a precursor thereof, the lithium ion conductive material comprising elemental phosphorus and one or more elements selected from lithium, boron, sulfur, and oxygen. 17. The method for producing a cathode composite according to any one of 13 to 16, wherein the ion conductor is phosphorus sulfide. 18. The method for producing a cathode composite according to any one of 13 to 17, wherein the ion conductor comprises diphosphorus pentasulfide. 19. The manufacturing method according to any one of 13 to 18, wherein the sulfur-based active material contains elemental sulfur. 20. The manufacturing method according to any one of 13 to 19, wherein the mass ratio of the sulfur-based active material, the carbon material, and the ion conductor satisfies the following relationship:(sulfur-based active material + carbon material): ionic conductor = 50: 1 to 80 21. The manufacturing method according to any one of 13 to 20, wherein the mass ratio of the total of the sulfur-based active material and ionic conductor to the carbon material is less than 5.00. 22. A positive electrode comprising the positive electrode mixture according to any one of 1 to 12. 23. A lithium ion battery comprising the positive electrode mixture according to any one of 1 to 12 or the positive electrode of 22.

[0007] The present invention provides a positive electrode composite that can improve the charge-discharge characteristics of lithium-ion batteries. Furthermore, the amount of solid electrolyte used, which is often produced through a complex manufacturing process, can be reduced, which is expected to result in cost savings.

[0008] 1 is a P2p spectrum of Example 1. 2 is a P2p spectrum of Example 2. 3 is a P2p spectrum of Example 3. 4 is a P2p spectrum of Example 4. 5 is a P2p spectrum of Example 5. 6 is a P2p spectrum of Example 6. 7 is a P2p spectrum of Example 7. 8 is a P2p spectrum of Comparative Example 2. 9 is a P2p spectrum of Reference Example 1. 10 is a P2p spectrum of Reference Example 2. 11 is a P2p spectrum of Reference Example 3. 12 is a P2p spectrum of the solid of Example 1. ３１ 1 shows the results of waveform separation of the P-NMR spectrum. ３１ 1 is a result of waveform separation of P-NMR spectra; FIG. 2 is an X-ray diffraction (XRD) chart of Example 1; FIG. 3 is an XRD chart of Example 2; FIG. 4 is an XRD chart of Example 3; FIG. 5 is an XRD chart of Example 4; FIG. 6 is an XRD chart of Comparative Example 2; and FIG. 7 is an XRD chart of Comparative Example 3.

[0009] 1. First embodiment of positive electrode composite A positive electrode composite according to one embodiment of the present invention includes a sulfur-based active material, a carbon material having micropores, an ionic conductor containing phosphorus and / or a modified version of the ionic conductor, and a solid electrolyte. Furthermore, in a P2p spectrum obtained by surface elemental analysis using X-ray photoelectron spectroscopy, the positive electrode composite satisfies at least one of the following formulas (1) and (2): Ａ / I Ｂ >0.50 (1) I Ｃ / I Ｂ >1.20 (2) (wherein, I Ａis the signal intensity at position A where the binding energy is around 135.4 eV, I Ｂ is the signal intensity at position B where the binding energy is around 134.25 eV, I Ｃ is the signal intensity at position C where the binding energy is near 133.0 eV.) Note that "near" means that the position of the binding energy may vary slightly depending on the measurement device, etc., but for example, position A means a peak that appears in the range of 135.0 eV or more and 136.5 eV or less, position B means a peak that appears in the range of 133.5 eV or more but less than 134.5 eV, and position C means a peak that appears in the range of 132.0 eV or more but less than 133.3 eV. Furthermore, if no clear peak appears at each position, 135.4 eV is designated as position A, 134.25 eV as position B, and 133.0 eV as position C.

[0010] Position B of the P2p spectrum is P ２ S ５ The signal intensity at position B is P ２ S ５ The signal intensities at positions A and C are derived from the denatured form of the ion conductor. Ａ / I Ｂ and I Ｃ / I Ｂ The fact that is large means that P ２ S ５ The positive electrode mixture of the present embodiment has a higher signal intensity ratio I Ａ / I Ｂ and I Ｃ / I Ｂ At least one of the above is increased. This is thought to indicate that the sulfur-based active material, the carbon material, the ionic conductor, and the modified ionic conductor form an interface in a form different from conventional forms. As a result, an ionic conduction path is efficiently formed within the positive electrode composite, resulting in a positive electrode composite that can improve the charge / discharge characteristics of lithium-ion batteries. Details of the P2p spectrum analysis are as described in the Examples.

[0011] In one embodiment, I Ｃ / I Ｂis preferably greater than 1.30, more preferably 1.30 or greater, even more preferably 1.40 or greater, and particularly preferably 1.60 or greater. Ｃ / I Ｂ is, for example, 3.00 or less.

[0012] In the positive electrode composite according to one embodiment of the present invention, the rate of change in the carbon to phosphorus element ratio C / P before and after Ar sputtering is 0.550 or more, as determined by surface elemental analysis using X-ray photoelectron spectroscopy.

[0013] The Ar sputtering process is a process for scraping the surface layer of the positive electrode composite material and measuring the internal state of the positive electrode composite material. Ａ ) indicates the change in element ratio between the outermost surface and the interior of the positive electrode composite, and is calculated using the following formula: Ａ = (internal element ratio C / P) / (surface element ratio C / P) R Ａ is 1 means that the elemental composition of the interior and the surface is equal, and as the difference from 1 increases, the difference in elemental composition between the interior and the surface increases. Due to the influence of the sputtering rate of Ar sputtering, the elemental ratio C / P tends to be smaller in the interior than on the surface. On the other hand, in the positive electrode composite of this embodiment, there is a tendency for phosphorus (P) to be unevenly distributed on the surface and carbon (C) to be unevenly distributed in the interior. From the relationship between the influence of Ar sputtering and the properties of the positive electrode composite, in the positive electrode composite of this embodiment, the rate of change of the elemental ratio C / P (R Ａ ) becomes large, reaching 0.550 or more. The rate of change of the element ratio C / P is preferably 0.600 or more, more preferably 0.650 or more, and particularly preferably 0.700 or more. The rate of change of the element ratio C / P is, for example, 0.900 or less. Details of the measurement of the rate of change of the element ratio C / P are as described in the Examples.

[0014] The positive electrode mixture according to one embodiment of the present invention is a solid ３１ In the P-NMR measurement, P ２ S ６ ４－ Peak and PS ３ － The total area of ​​the peaks is 20% or more of the total. ３１The state of the phosphorus element near the surface of the positive electrode mixture can be confirmed by P-NMR measurement. In this embodiment, the sulfur-based active material, the carbon material, the ion conductor, and the modified ion conductor form an interface in a form different from conventional ones. ２ S ６ ４－ Peak and PS ３ － The fact that the total area of ​​the peaks is 20% or more of the total indicates that the interface is different from that of conventional positive electrode mixtures.

[0015] The positive electrode mixture according to one embodiment of the present invention is a solid ３１ In the P-NMR measurement, P ２ S ５ As described above, in this embodiment, the sulfur-based active material, the carbon material, the ion conductor, and the modified ion conductor form an interface in a form different from that of the conventional one. As a result, P ２ S ５ The area of ​​the peak is 25% or less of the total. ３１ The details of the P-NMR measurement are as described in the Examples.

[0016] In one embodiment, the positive electrode composite includes a sulfur-based active material, a carbon material having micropores, at least one of an ion conductor and a modified version of the ion conductor, and a solid electrolyte, and has a specific surface area parameter x of 5.00 or less. In one embodiment, the positive electrode composite includes a sulfur-based active material, a carbon material having micropores, at least one of an ion conductor and a modified version of the ion conductor, and a solid electrolyte, and the ion conductor is amorphous.

[0017] In one embodiment, the mass ratio of the sulfur-based active material (S), the ionic conductor containing elemental phosphorus, and the modified ionic conductor to the carbon material (C) is less than 5.00. For example, when the ionic conductor is diphosphorus pentasulfide, the mass ratio [(S + P ２ S ５) / C] is smaller than 5.00. When the mass ratio is less than 5.00, the charge / discharge characteristics are further improved. The mass ratio may be 4.80 or less, 4.50 or less, 4.30 or less, 4.00 or less, 3.70 or less, or 3.50 or less. The mass ratio can be adjusted by the amount of each constituent material.

[0018] 2. Manufacturing Method of Cathode Composite The cathode composite of this embodiment can be manufactured by the method of the present invention, for example, including the following steps. Step (A): A cathode composite precursor is prepared by mixing at least one of a composite and a mixture of a sulfur-based active material and a porous carbon material with a molten ion conductor. Step (B): A cathode composite is manufactured by mixing and pulverizing the cathode composite precursor of step (A) and a solid electrolyte. In one embodiment, the cathode composite is obtained by the manufacturing method of the present invention. Hereinafter, the manufacturing methods of the cathode composite precursor and the cathode composite will be described.

[0019] [Step (A)] In step (A), at least one of a composite and a mixture of a sulfur-based active material and a porous carbon material is mixed with a molten ion conductor to prepare a positive electrode composite precursor.

[0020] The sulfur-based active material is not particularly limited, but sulfur, lithium sulfide (Li ２ S), lithium polysulfide (Li ２ S ｎ : n satisfies 1<n≦8.), titanium sulfide (TiS ２ ), molybdenum sulfide (MoS ２ ), iron sulfide (FeS, FeS ２ ), copper sulfide (CuS), nickel sulfide (Ni ３ S ２ ), sulfur-containing polymer compounds, etc. Among these, sulfur is preferred. There are no particular limitations on the sulfur, but sulfur with a high purity is preferred. Specifically, the purity is preferably 95% by mass or more, more preferably 96% by mass or more, and particularly preferably 97% by mass or more. Examples of the crystal system of sulfur include α sulfur (orthorhombic system), β (monoclinic system), γ (monoclinic system), amorphous sulfur, etc. These can be used alone or in combination of two or more types.

[0021] As the ion conductor, a lithium ion conductive material containing phosphorus or a precursor thereof can be used. Examples of the lithium ion conductive material include a lithium ion conductive material containing one or more elements selected from lithium, boron, oxygen, sulfur, phosphorus, halogens, and antimony, or a precursor thereof. A lithium ion conductive material containing phosphorus and one or more elements selected from lithium, boron, sulfur, and oxygen, or a precursor thereof, is preferred. A lithium ion conductive material that does not contain phosphorus can be used in combination with a lithium ion conductive material containing phosphorus.

[0022] In this specification, a "lithium ion conductive material containing one or more elements selected from lithium, boron, oxygen, sulfur, phosphorus, a halogen, and antimony" refers to a material that remains solid at 25°C under a nitrogen atmosphere and has ionic conductivity attributable to lithium ions. Also, a "precursor of a lithium ion conductive material containing one or more elements selected from lithium, boron, oxygen, phosphorus, a halogen, and antimony" refers to a material that, when used as an active material in a lithium ion battery, reacts with lithium metal or lithium ions to form a lithium-containing compound, thereby becoming the lithium ion conductive material.

[0023] As used herein, the term "halogen" includes elements such as fluorine, chlorine, bromine, and iodine.

[0024] Since the ionic conductor is heated to form a melt, the melting point is preferably 130 to 450°C, and more preferably 220 to 450°C. Furthermore, the melting point of the ionic conductor is preferably lower, such as 440°C or lower, 430°C or lower, 420°C or lower, 410°C or lower, or 400°C or lower. Elemental sulfur, which is an example of a sulfur-based active material, has a boiling point of approximately 450°C. Mixing it with a melt of a substance having a melting point higher than this will volatilize the material, and it is believed that the desired positive electrode composite precursor cannot be obtained. Furthermore, lowering the temperature in the process reduces the energy required for production, leading to lower costs.

[0025] Lithium ion conductive material: lithium borohydride, LiBF ４, organic lithium salts, polymer electrolytes such as polyethylene oxide, etc. Precursors of lithium ion conductive materials include phosphorus sulfides such as diphosphorus pentasulfide, red phosphorus, boron sulfide, diphosphorus pentoxide, tin, etc. These compounds may be used alone or in combination of two or more.

[0026] Examples of organic lithium salts include bis(perfluoroalkylsulfonyl)imide lithium salts such as bis(trifluoromethanesulfonyl)imide lithium, bis(fluorosulfonyl)imide lithium, fluorosulfonyl-trifluoromethanesulfonylimide lithium, bis(pentafluoroethanesulfonyl)imide lithium, and bis(nonafluorobutanesulfonyl)imide lithium; lithium salts of perfluoroalkylsulfonimides such as 4,4,5,5-tetrafluoro-1,3,2-dithiazolidine-1,1,3,3-tetraoxide lithium salt; lithium salts of fluorosulfonylimides; lithium carboxylic acid salts such as trifluoromethanesulfonic acid, lithium acetate, lithium propionate, and lithium butyrate; lithium organic sulfonates such as lithium dodecylbenzenesulfonate and lithium p-styrenesulfonate; and lithium organic phosphates. These organic lithium salts are also preferably used together with ion-conductive polymers and ionic liquids, as they are expected to provide higher lithium conductivity.

[0027] The ionic conductor is preferably one or more compounds selected from the group consisting of phosphorus sulfide, red phosphorus, boron sulfide, diphosphorus pentoxide, and polymer electrolytes such as polyethylene oxide, which are substantially free of lithium element. Ionic conductors that are substantially free of lithium element are considered to have high affinity with sulfur-based active materials and carbon materials.

[0028] More preferably, the ionic conductor is one or more compounds selected from the group consisting of phosphorus sulfide, red phosphorus, and diphosphorus pentoxide. ４ S ３ ), diphosphorus pentasulfide (P ２ S ５ ), phosphorus heptasulfide (P ４ S ７), tetraphosphorus pentasulfide (P ４ S ５ ) and the like. Furthermore, phosphorus sulfide may have a dimer or polysulfide structure, or may be a mixture. Particularly preferably, the ionic conductor is diphosphorus pentasulfide, which is expected to react with lithium to form a sulfide solid electrolyte exhibiting high ionic conductivity. The content of phosphorus sulfide or diphosphorus pentasulfide relative to the entire ionic conductor is 50% by mass or more, 80% by mass or more, 95% by mass or more, or 99% by mass or more, and is substantially 100% by mass. When it is substantially 100% by mass, it may contain unavoidable impurities.

[0029] Examples of carbon materials having micropores include carbon black such as Ketjen black, acetylene black, Denka black, thermal black, channel black, and Knobel (registered trademark), graphite, activated carbon, etc. These may be used alone or in combination of two or more.

[0030] In one embodiment, the BET specific surface area of ​​the carbon material is 50 m ２ / g or more, 6000m ２ This allows a wide contact interface between the carbon material and the sulfur-based active material to be formed, improving the utilization rate of the sulfur-based active material. ２ / g or more, 100m ２ / g or more, 1000m ２ / g or more, 1500m ２ / g or more, 2000m ２ / g or more, 2500m ２ / g or more or 3000m ２ / g or more. ２ / g or less, and more preferably 5000m ２ / g or less is preferred.

[0031] In addition, the pore volume of the carbon material is 0.5 cm ３ / g or more, 6cm ３ This allows the sulfur-based active material to be impregnated into the pores of the carbon material, further improving the battery capacity. ３ / g or more, and more preferably 1.0 cm３ / g or more is preferable. ３ / g or less, and more preferably 5.0 cm ３ / g or less is preferred.

[0032] In the present invention, the BET specific surface area and pore volume can be determined using a nitrogen adsorption isotherm obtained by adsorbing nitrogen gas to a carbon material at liquid nitrogen temperature. Specifically, the BET specific surface area can be calculated by the Brenauer-Emmet-Telle (BET) multipoint method using the nitrogen adsorption isotherm. Furthermore, the pore volume can be determined by the Barret-Joyner-Halenda (BJH) method using the nitrogen adsorption isotherm. As a measuring device, for example, a specific surface area / pore distribution measuring device (Autosorb-3) manufactured by Quantacrome can be used for the measurement.

[0033] In the manufacturing method of this embodiment, at least one of the composite and mixture of the sulfur-based active material and the carbon material having pores is mixed with a molten ion conductor. In one embodiment, a composite of the sulfur-based active material and the carbon material having pores is prepared in advance, and then the composite is mixed with the molten ion conductor. As a result, the ion conductor is coated on the surface of the composite, i.e., on both the sulfur-based active material and the carbon material, and an ion conduction path between the three is efficiently formed. On the other hand, when a mixture of the sulfur-based active material and the carbon material having pores is mixed with a molten ion conductor, it is believed that the sulfur-based active material, which has a lower melting point than the ion conductor, melts first, thereby forming a composite of the sulfur-based active material and the carbon material having pores, and then the ion conductor melts, thereby forming a similar structure.

[0034] In one embodiment, the mass ratio of the sulfur-based active material (S) to the carbon material (C) is 1:9 to 9:1, preferably 5:5 to 9:1.

[0035] The method for compounding the sulfur-based active material and the carbon material having pores is not particularly limited. For example, the sulfur-based active material and the carbon material may be mixed and crushed using a mixer / crusher such as a planetary ball mill to compound them, or the sulfur-based active material and the carbon material may be heated in a sealed state to a temperature equal to or higher than the melting point of the sulfur-based active material to compound them.

[0036] At least one of the composite and mixture of the sulfur-based active material and the porous carbon material can be mixed with the molten ionic conductor by heating at a temperature equal to or higher than the melting point of the ionic conductor. The heating temperature is adjusted according to the ionic conductor used. Substances that are sublimable at normal pressure can be mixed in a molten state by applying pressure. The heating time is preferably 10 minutes to 24 hours. A positive electrode composite precursor is obtained by cooling after heating. If necessary, a pulverization step may be performed after cooling.

[0037] In one embodiment, the mass ratio of the sulfur-based active material, the carbon material, and the ionic conductor in the positive electrode composite precursor satisfies the following relationship: (sulfur-based active material + carbon material): ionic conductor = 50:1 to 80, preferably (sulfur-based active material + carbon material): ionic conductor = 50:5 to 60.

[0038] In one embodiment, the mass ratio of the total of the sulfur-based active material (S) and the ionic conductor to the carbon material (C) is less than 5.00. For example, when the ionic conductor is diphosphorus pentasulfide, the mass ratio [(S + P ２ S ５ ) / C] is smaller than 5.00. When the mass ratio is less than 5.00, the charge / discharge characteristics are further improved. The mass ratio may be 4.80 or less, 4.50 or less, 4.30 or less, 4.00 or less, 3.70 or less, or 3.50 or less. The mass ratio may be 2.00 or more, 2.60 or more, or 3.20 or more. The mass ratio can be adjusted by the amount of each constituent material.

[0039] [Step (B)] In step (B), the cathode composite precursor of step (A) and a solid electrolyte are mixed and pulverized to produce a cathode composite. The solid electrolyte is not particularly limited, but examples thereof include sulfide solid electrolytes used in lithium ion batteries, which will be described later.

[0040] The mixing of the cathode composite precursor and the solid electrolyte is not particularly limited and can be adjusted according to the characteristics of the solid electrolyte used. For example, if the solid electrolyte is crystalline and maintaining the crystallinity affects performance, the cathode composite precursor and the solid electrolyte are mixed using a relatively weak force. Examples of devices for mixing the cathode composite precursor and the solid electrolyte include a planetary ball mill, a tumbling mill, a bead mill, a Filmix, a Nauta mixer, a tornado mixer, a twin-screw extruder, a multi-screw roller, and a solid-state shear kneader.

[0041] In one embodiment, the solid electrolyte is a crystalline solid electrolyte, and the cathode composite is produced by mixing and pulverizing the solid electrolyte under conditions that do not cause the crystallinity of the solid electrolyte to be lost. To perform mixing and pulverizing under conditions that do not cause the crystallinity to be lost, for example, a device with a relatively small impact force, such as a tumbling mill, may be used. Furthermore, conditions such as the rotation speed may be adjusted to mix and pulverize the solid electrolyte under a lower load than usual. Whether the crystallinity of the solid electrolyte is maintained can be confirmed, for example, by the presence of a crystalline peak and a change in the half-width by X-ray diffraction measurement.

[0042] 3. Lithium-ion Battery A lithium-ion battery according to one embodiment of the present invention includes the above-described cathode composite of the present invention. For example, an all-solid-state lithium-ion battery can be manufactured by using a solid electrolyte instead of a liquid electrolyte. By using the cathode composite of the present invention, an all-solid-state lithium-ion battery with good charge / discharge characteristics can be manufactured. The all-solid-state lithium-ion battery will now be described. An all-solid-state lithium-ion battery is primarily composed of a cathode layer, an anode layer, and an electrolyte layer, and the cathode composite of the present invention is suitable as a constituent material for the cathode layer. The anode layer and electrolyte layer can be manufactured by known methods. In addition to the cathode layer, anode layer, and electrolyte layer, a current collector is preferably used, and known current collectors can also be used.

[0043] The solid electrolyte is not particularly limited, but examples thereof include sulfide solid electrolytes. The sulfide solid electrolyte is a solid electrolyte that contains at least sulfur atoms and exhibits ionic conductivity due to lithium ions, and contains, in addition to sulfur atoms, preferably lithium atoms and phosphorus atoms, more preferably lithium atoms, phosphorus atoms, and halogen atoms, and has ionic conductivity due to lithium atoms. The sulfide solid electrolyte may be an amorphous sulfide solid electrolyte or a crystalline sulfide solid electrolyte.

[0044] (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 lithium ions. 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., a solid electrolyte composed of lithium sulfide, phosphorus sulfide, and lithium halide; ２ S-P ２ S ５ -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.

[0045] 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 65 to 85:15 to 35, more preferably 70 to 80:20 to 30, and even more preferably 72 to 78:22 to 28. ２ S-P ２ S ５ In the case of -LiI-LiBr, the total content of lithium sulfide and diphosphorus pentasulfide is preferably 60 to 95 mol%, more preferably 65 to 90 mol%, and even more preferably 70 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%.

[0046] When the amorphous sulfide solid electrolyte contains lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms, the compounding ratio (molar ratio) of these atoms is preferably 1.0 to 1.8: 1.0 to 2.0: 0.1 to 0.8: 0.01 to 0.6, more preferably 1.1 to 1.7: 1.2 to 1.8: 0.2 to 0.6: 0.05 to 0.5, and even more preferably 1.2 to 1.6: 1.3 to 1.7: 0.25 to 0.5: 0.08 to 0.4. Furthermore, when bromine and iodine are used in combination as halogen atoms, the compounding ratio (molar ratio) of lithium atoms, sulfur atoms, phosphorus atoms, bromine atoms, and iodine atoms is preferably 1.0 to 1.8: 1.0 to 2.0: 0.1 to 0.8: 0.01 to 0.3: 0.01 to 0.3, more preferably 1.1 to 1.7: 1.2 to 1.8: 0.2 to 0.6: 0.02 to 0.25: 0.02 to 0.25, more preferably 1.2 to 1.6: 1.3 to 1.7: 0.25 to 0.5: 0.03 to 0.2: 0.03 to 0.2, and even more preferably 1.35 to 1.45: 1.4 to 1.7: 0.3 to 0.45: 0.04 to 0.18: 0.04 to 0.18. By setting the compounding ratio (molar ratio) of lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms within the above range, it becomes easier to obtain a solid electrolyte having a thiolisiconregion II type crystal structure described below and having higher ionic conductivity.

[0047] 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.

[0048] (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).

[0049] The crystalline sulfide solid electrolyte containing lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms may have a crystal structure such as Li ４－ｘ Ge １－ｘ P ｘ S ４ Thio-LISICON Region II crystal structure (Kanno et al., Journal of the Electrochemical Society, 148(7)A742-746(2001)), Li ４－ｘ Ge １－ｘ P ｘ S ４ Examples of the thio-lisicon region II crystal structure include those having a crystal structure similar to the thio-lisicon region II type (see Solid State Ionics, 177 (2006), 2721-2725). ４－ｘ Ge １－ｘ P ｘ S ４ Thio-LISICON Region II crystal structure, Li ４－ｘ Ge １－ｘ P ｘ S ４This indicates that the thio-LISICON region II type has a similar crystal structure.

[0050] 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°.

[0051] 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 S６ 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).

[0052] 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.

[0053] 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.

[0054] 4. Other Forms of Cathode Composite A cathode composite according to one embodiment of the present invention includes a sulfur-based active material, a carbon material having micropores, at least one of an ion conductor and a modified form of the ion conductor, and a solid electrolyte, and has a change rate of the elemental ratio C / P of carbon to phosphorus, C / P, of 0.550 or more before and after Ar sputtering treatment, as determined by surface elemental analysis using X-ray photoelectron spectroscopy.

[0055] A positive electrode composite according to one embodiment of the present invention includes a sulfur-based active material, a carbon material having micropores, an ion conductor and / or a modified form of the ion conductor, and a solid electrolyte, wherein the ion conductor includes phosphorus sulfide, and the solid ３１ In the P-NMR measurement, P ２ S ６ ４－ Peak and PS ３－ The total area of ​​the peaks is 20% or more of the total.

[0056] A positive electrode composite according to one embodiment of the present invention includes a sulfur-based active material, a carbon material having micropores, an ion conductor and / or a modified form of the ion conductor, and a solid electrolyte, wherein the ion conductor includes phosphorus sulfide, and the solid ３１ In the P-NMR measurement, P ２ S ５ The area of ​​the peak is 25% or less of the total.

[0057] The positive electrode mixtures of the above-mentioned respective embodiments can all be obtained by, for example, the above-mentioned manufacturing method of the present invention.

[0058] [Solid Electrolyte] Production Example 1 (Preparation of Solid Electrolyte A) 0.4398 g of lithium sulfide, 0.7084 g of diphosphorus pentasulfide, 0.2133 g of lithium iodide, 0.1384 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) at a rotation speed of 370 rpm for 40 hours to obtain a powder. The obtained powder was heated at 195 ° C. for 3 hours to obtain a solid electrolyte A.

[0059] Production Example 2 (Preparation of Solid Electrolyte B) 15.3 g of lithium sulfide and 24.7 g of diphosphorus pentasulfide were placed in a 1 L reactor equipped with a stirring blade under a nitrogen atmosphere. After the stirring blade was turned on, 400 mL of tetrahydrofuran cooled to -20°C was added to the vessel. After allowing the temperature to rise naturally to room temperature and stirring for 72 hours, the resulting reaction solution slurry was placed in a glass filter (pore size: 40 to 100 μm) to obtain a solid content. The solid content was dried at 90°C to obtain Li ３ P.S. ４ The obtained Li powder (purity: 90% by mass) was placed in a Schlenk flask (volume: 100 mL) equipped with a stirrer under a nitrogen atmosphere. ３ P.S. ４1.70 g of powder, 0.19 g of lithium bromide, and 0.28 g of lithium iodide were added. After rotating the stirrer, 20 mL of the complexing agent tetramethylethylenediamine (TMEDA) was added and stirred for 12 hours. The obtained electrolyte precursor content was dried under vacuum at room temperature to obtain a powdered electrolyte precursor. The obtained electrolyte precursor was heated under vacuum at 120°C for 2 hours, and further heated under vacuum at 140°C for 2 hours to obtain solid electrolyte B.

[0060] Production Example 3 (Preparation of Solid Electrolyte C) Lithium sulfide (Li ２ S), diphosphorus pentasulfide (P ２ S ５ ), lithium bromide (LiBr) and lithium chloride (LiCl) in a molar ratio of Li ２ S:P ２ S ５ The raw materials were roughly mixed to obtain a ratio of 47.5:12.5:15.0:25.0 of LiBr:LiCl. The raw material mixture was dispersed in a mixed solvent of dehydrated toluene and 2% by mass of dehydrated isobutyronitrile relative to the raw material mixture to obtain a slurry of approximately 10% by mass. A bead mill was operated at a peripheral speed of 12 m / s and a flow rate of 500 mL / min, and the slurry was introduced into the mill and circulated for 1 hour to obtain a mixture. After removing the solvent from the obtained mixture, the mixture was heated at 400 to 430 °C for 2 hours in an electric furnace. The mixture was then slowly cooled to obtain a raw material sulfide solid electrolyte. The raw material sulfide solid electrolyte was dispersed in dehydrated toluene under a nitrogen atmosphere and placed in a zirconia pot of a planetary ball mill (manufactured by Fritsch: model number P-7) together with 0.3 mm diameter zirconia balls, and the pot was filled with an inert atmosphere. The planetary ball mill was rotated at 150 rpm for 2 hours to obtain a slurry containing a finely divided sulfide solid electrolyte. The slurry was transferred to a nitrogen-substituted Schlenk flask, dried at room temperature for 1 hour using a vacuum pump, and then heated to 80°C to 100°C to further remove the solvent contained in the finely divided sulfide solid electrolyte (drying under reduced pressure), thereby obtaining solid electrolyte C.

[0061] [Positive electrode composite] Example 1 (1) Preparation of activated carbon and sulfur composite (S-C composite) Activated carbon (MSC-30SSS, manufactured by Kansai Thermal Chemical Co., Ltd.) and sulfur were placed in a glass bottle in a mass ratio of 3:7, 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 a powder of activated carbon and sulfur composite.

[0062] (2) Preparation of a cathode composite precursor The composite powder obtained in (1) above and diphosphorus pentasulfide (manufactured by Italmatch, melting point 286 to 290°C) were placed in a Tammann tube with an inner diameter of 12 mm in a mass ratio of 0.7143:0.2857, and the resulting mixture was sealed in an SUS tube. The mixture was heated in an electric furnace at 350°C for 6 hours to obtain a cathode composite precursor.

[0063] (3) Preparation of Positive Electrode Composite: 0.6300 g of the positive electrode composite precursor (2) above and 0.2700 g of solid electrolyte A were placed in a 45 mL zirconia pot together with 34 g of zirconia balls with a diameter of 2 mm, and the pot was sealed. Using a tumbling mill ("Small Ball Mill Stand," manufactured by Asahi Rika Seisakusho, Model AV-1), mixing was carried out at room temperature at a rotation speed of 600 rpm for 1 hour to obtain a powder of the positive electrode composite.

[0064] Example 2 A positive electrode composite precursor was prepared in the same manner as in Example 1, except that the powder of the S-C composite obtained in Example 1 (1) above and diphosphorus pentasulfide (manufactured by Italmatch, melting point 286 to 290°C) were placed in a Tammann tube having an inner diameter of 12 mm in a mass ratio of 0.8333:0.1667. A positive electrode composite powder was obtained in the same manner as in Example 1, except that 0.5400 g of the positive electrode composite precursor and 0.3600 g of solid electrolyte A were used.

[0065] Example 3 A powder of a positive electrode mixture was obtained in the same manner as in Example 1, except that 0.6300 g of the positive electrode mixture precursor prepared in Example 1(2) and 0.2700 g of solid electrolyte B were used.

[0066] Example 4 A powder of a positive electrode mixture was obtained in the same manner as in Example 1, except that 0.6300 g of the positive electrode mixture precursor prepared in Example 1(2) and 0.2700 g of solid electrolyte C were used.

[0067] Example 5 (1) Preparation of a positive electrode composite precursor Activated carbon (Kansai Ceramic Chemicals, MSC-30SSS), sulfur, and diphosphorus pentasulfide (Italmatch, melting point 286 to 290°C) were placed in a Tammann tube with an inner diameter of 12 mm in a mass ratio of 0.2143:0.5000:0.2857, and the tube was sealed in an SUS tubular container. The mixture was heated in an electric furnace at 350°C for 6 hours to obtain a positive electrode composite precursor.

[0068] (2) Preparation of Cathode Composite: 0.6300 g of the cathode composite precursor (1) above and 0.2700 g of solid electrolyte C were placed in a 45 mL zirconia pot together with 34 g of zirconia balls with a diameter of 2 mm, and the pot was sealed. Using a tumbling mill ("Small Ball Mill Stand," manufactured by Asahi Rika Seisakusho, Model AV-1), mixing was carried out at room temperature at a rotation speed of 600 rpm for 1 hour to obtain a powder of the cathode composite.

[0069] Example 6 (1) Preparation of activated carbon and sulfur composite (S-C composite) A powder of an activated carbon and sulfur composite was obtained in the same manner as in Example 1. (2) Preparation of cathode composite precursor A cathode composite precursor was obtained in the same manner as in Example 1, except that the powder of the composite obtained in (1) above, diphosphorus pentasulfide (manufactured by Italmatch, melting point 286-290°C), and sulfur were placed in a Tammann tube with an inner diameter of 12 mm in a mass ratio of 0.7143:0.2143:0.0714. (3) Preparation of cathode composite A powder of a cathode composite was obtained in the same manner as in Example 1, except that 0.6300 g of the cathode composite precursor prepared in (2) above and 0.2700 g of solid electrolyte C were used.

[0070] Example 7 (1) Preparation of activated carbon and sulfur composite (S-C composite) A powder of an activated carbon and sulfur composite was obtained in the same manner as in Example 1. (2) Preparation of positive electrode composite precursor A positive electrode composite precursor was obtained in the same manner as in Example 1, except that the powder of the composite obtained in (1) above, diphosphorus pentasulfide (manufactured by Italmatch, melting point 286-290°C), and sulfur were placed in a Tammann tube with an inner diameter of 12 mm in a mass ratio of 0.6667:0.2666:0.0667. (3) Preparation of positive electrode composite A powder of a positive electrode composite was obtained in the same manner as in Example 1, except that 0.6750 g of the positive electrode composite precursor prepared in (2) above and 0.2250 g of solid electrolyte C were used.

[0071] Comparative Example 1 0.4500 g of powder of the S—C composite obtained in the same manner as in Example 1(1) and 0.4500 g of solid electrolyte A were mixed in a tumbling mill in the same manner as in Example 1(3) to obtain a powder of a positive electrode mixture.

[0072] Comparative Example 2 0.4500 g of powder of the S-C composite obtained in the same manner as in Example 1(1), 0.1800 g of diphosphorus pentasulfide, and 0.2700 g of solid electrolyte A were mixed in a tumbling mill in the same manner as in Example 1(3) so that the mass ratio of activated carbon, sulfur, and diphosphorus pentasulfide was the same as in Example 1, to obtain a powder of a positive electrode composite.

[0073] Comparative Example 3 0.4500 g of powder of the S-C composite obtained in the same manner as in Example 1(1), 0.0900 g of diphosphorus pentasulfide, and 0.3600 g of solid electrolyte A were mixed in a tumbling mill in the same manner as in Example 1(3) so that the mass ratio of activated carbon, sulfur, and diphosphorus pentasulfide was the same as in Example 2, to obtain a powder of a positive electrode composite.

[0074] Reference Example 1 A positive electrode composite precursor was obtained in the same manner as in Example 1(2), except that the powder of the S—C composite obtained in Example 1(1) above and diphosphorus pentasulfide (manufactured by Italmatch, melting point 286 to 290° C.) were placed in a Tammann tube having an inner diameter of 12 mm in a mass ratio of 0.7143:0.2857.

[0075] Reference Example 2 A positive electrode composite precursor was obtained in the same manner as in Example 1(2), except that the powder of the S—C composite obtained in Example 1(1) above and diphosphorus pentasulfide (manufactured by Italmatch, melting point 286 to 290° C.) were placed in a Tammann tube having an inner diameter of 12 mm in a mass ratio of 0.8333:0.1667.

[0076] Reference Example 3 The powder of the S-C composite obtained in Example 1 (1) above and diphosphorus pentasulfide (manufactured by Italmatch, melting point 286 to 290°C) were charged into an agate mortar in a mass ratio of 0.7143:0.2857 and mixed for 5 minutes to obtain a positive electrode composite precursor.

[0077] [Evaluation] The following evaluations were performed on the positive electrode composites prepared in the examples and comparative examples. (1) X-ray photoelectron spectroscopy (XPS) measurement (a) XPS measurement In a glove box controlled to an Ar atmosphere with a dew point of -60°C or less, double-sided carbon tape was attached to a metal substrate, and a powder sample was pressed onto the tape with a spatula. The surface of the spatula used was cleaned with an organic solvent such as acetone. A metal perforated mask (hole diameter 5 mm) was placed on the tape with the powder sample fixed and fixed with screws to prepare a measurement sample. To prevent the sample from being exposed to the atmosphere, a transfer vessel was used to introduce the sample into the XPS apparatus, and measurements were performed. Detailed measurement conditions for XPS are shown below.

[0078] XPS apparatus: VersaProbe II (ULVAC-PHI, Inc.) X-ray source: Monochromated AlKα radiation (1486.6 eV) measured at a high power of 100 W X-ray diameter: 100 μm (measured by sweeping over a range of 200 μm x 1200 μm) Pass energy: 23.5 eV (C1s, S2p, P2p) 46.95 eV (O1s, Li1s, Br3d, I3d5 / 2, Cl2p) Step energy: 0.1 eV (C1s, S2p, P2p) 0.2 eV (O1s, Li1s, Br3d, I3d5 / 2, Cl2p) Photoelectron detection angle: 45°

[0079] The XPS measurement was performed on two samples: the surface (outermost surface) of the sample and the inside A of the sample where the surface layer was cut off. The sample surface was not subjected to the surface treatment described later. －７ The measurement was performed immediately after introducing the sample into a vacuum (less than 100 Pa). Sample inside A was measured after surface treatment using the following sputter ion gun. Sample inside A: Ar monomer ions: 1 kV, 7 mA, 2 mm x 2 mm, 60 minutes

[0080] (b) Relative peak intensity of the sample surface in the P2p spectrum. The analysis software used was MultiPak manufactured by ULVAC-PHI. ８The peak position of the P2p orbital was set to 164.1 eV for charge correction. The background of the spectrum derived from the P2p orbital was subtracted by the Shirley method, and the cps values ​​(signal intensity: I) were extracted for three peaks: a peak with a binding energy of approximately 135.4 eV (Peak A), a peak with a binding energy of approximately 134.25 eV (Peak B), and a peak with a binding energy of approximately 133.0 eV (Peak C). The signal intensity ratio (I Ａ / I Ｂ and I Ｃ / I Ｂ ) was calculated. Note that "near" means that the position of the binding energy may vary slightly depending on the measurement device, etc., but for example, position A means a peak that appears in the range of 135.0 eV to 136.5 eV, position B means a peak that appears in the range of 133.5 eV to less than 134.5 eV, and position C means a peak that appears in the range of 132.0 eV to less than 133.3 eV. Furthermore, if no clear peak appears at each position, 135.4 eV is designated as position A, 134.25 eV as position B, and 133.0 eV as position C. The P2p relative intensity on the sample surface is the value at one point near the center of the measurement area (diameter 5 mm). Note that it was confirmed that the spectra of each element were approximately the same at a total of three points in the measurement area: near the center and two points approximately 500 μm away from the center.

[0081] The P2p spectra of Examples 1 to 7 and Comparative Example 2 are shown in Figures 1 to 8. The P2p spectra of Reference Examples 1 to 3 are shown in Figures 9 to 11. In the figures, A indicates position A where the binding energy is around 135.4 eV, B indicates position B where the binding energy is around 134.25 eV, and C indicates position C where the binding energy is around 133.0 eV.

[0082] (c) Elemental ratio C / P of carbon and phosphorus elements Analysis software used was MultiPak manufactured by ULVAC-PHI. The background was subtracted from each spectrum by the Shirley method, and the elemental ratio C / P was calculated from the obtained area intensity using the relative sensitivity coefficient. The carbon element peak has a peak top near 278-298 eV, and the phosphorus element peak has a peak top near 123-143 eV. The elemental ratio C / P on the sample surface was taken as the average value of three arbitrary points within the measurement area (diameter 5 mm). The elemental ratio C / P in the sample interior A was taken as the value of one arbitrary point within the measurement area. The C / P change rate R between the surface and interior A Ａ was calculated using the following formula: Ａ = (element ratio C / P in sample interior A) / (element ratio C / P on surface) The evaluation results of the XPS measurement are shown in Table 1.

[0083] *The parentheses in the solid electrolyte indicate the type of solid electrolyte used (A, B, or C). ２ S ５ The "state of" is the S-C complex and P ２ S ５ This shows the state when mixed.

[0084] As shown in Table 1, in the example, the signal intensity ratio I Ａ / I Ｂ is greater than 0.50 or I Ｃ / I Ｂ In order to consider the results of this analysis, the P2p spectra of the positive electrode composite precursors of Reference Examples 1 to 3 are shown in FIGS. ２ S ５ The peak due to P appears at position B. In Reference Example 3, peak B appears clearly, and ２ S ５ It was suggested that P exists in its original chemical state. ２ S ５ In Reference Examples 1 and 2, in which P was mixed in a molten state with the SC composite, it was confirmed that peaks A and C appeared instead of peak B. Peaks A and C are P ２ S ５ This indicates the presence of modified P. ２ S５ It is believed that P exists in the positive electrode composite precursor in a chemical state different from the original state. ２ S ５ It is presumed that the peak contains elements such as O and C derived from activated carbon in addition to P and S in the activated carbon. Carbon materials such as activated carbon generally contain C and O. Peak A is the peak of molten P. ２ S ５ It is thought that this represents a component generated by a reaction between P and a part of the activated carbon inside or on the surface of the activated carbon. ２ S ５ Since the difference in bond energy between ２ S ５ It is not, but does not contain O or C, etc. ２ It is presumed that the components are Sx (5<x). ２ S ５ It is thought that the peak C is due to the influence of the component of peak A produced during melting of activated carbon, and the component produced inside or on the surface of activated carbon by reacting with sulfur in the molten state. ２ S ５ When comparing the results of Reference Examples 1 and 2, which have different blending amounts of P, Peak A has the same signal intensity, while Peak C has P ２ S ５ It was confirmed that the signal intensity was high in Reference Example 1, which contained a large amount of molten P. ２ S ５ It is thought that the change in the S-C complex is due to the reaction inside or on the surface of the activated carbon, which produces the component indicated by peak A first, and the remaining part changes to the component indicated by peak C, also inside or near the surface of the activated carbon, and both components coat the S-C complex. ２ S ５ This is thought to indicate that the S—C composite was coated with the SiO2 and a strong interface was formed.

[0085] From Table 1 and Figures 1 to 8, P in the molten state ２ S ５By mixing a solid electrolyte into the cathode composite precursor obtained by mixing the S-C composite, the peak shape changes, and the relationship between the three binding energies (A to C), i.e., the signal intensity ratio I Ａ / I Ｂ and signal intensity ratio I Ｃ / I Ｂ When a solid electrolyte is added to the cathode composite precursor of the above-mentioned Reference Example, the P that many sulfide-based solid electrolytes have is increased. ２ Sx (5<x), that is, the influence of the peak C component is considered to appear. From this point of view, in the comparative example, the shape of peak B and peak C is superimposed, and the remaining P ２ S ５ This is thought to indicate the presence of a solid electrolyte. In the examples, it can be seen that the influence of peak C is relatively increased, but ２ S ５ It can be seen that the final peak shape varies slightly depending on the amount of

[0086] Raw material blending ratio (sulfur (S): activated carbon (C): P ２ S ５ ) was 35:15:20, and Example 1 etc. used a positive electrode composite precursor in which P ２ S ５ When comparing Example 2 and the like, in which the compounding ratio of P is half that of Example 1, it can be seen that the relative intensity of Peak C is high in Example 1 and the like, and the relative intensity of Peak A is high in Example 2 and the like. This is because the intensity of Peak C increased as a result of the addition of the solid electrolyte in both Example 1 and the like, in which the relative intensity of Peak C is high, and Example 2 and the like, in which the relative intensity of Peak A is high, at the stage of the positive electrode composite precursor. ２ S ５ In a molten state, the cathode composite precursor is mixed with the S-C composite, and then a solid electrolyte is mixed therewith. ２ S ５ It is considered that the S-C composite is covered with the S-C composite, forming a strong interface, and the A / B of the positive electrode composite becomes a certain value (for example, 0.5) or more, or the C / B becomes a certain value (for example, 1.2) or more.

[0087] In addition, in the examples, the change rate of the C / P inside the positive electrode composite precursor relative to the C / P on the surface was large. This is also due to the same reason as above, that the S-C composite ２ S ５ and / or P ２ S ５ In the examples where the modified material of the present invention is coated, the proportion of each component differs between the surface and the interior very close to the surface, which is thought to have promoted uneven distribution of each component in the depth direction.

[0088] (2) Solid ３１ Area ratio of each phosphorus component by P-NMR measurement Measurement was performed using the following apparatus under the following conditions: Apparatus: ECZL400G (manufactured by JEOL Ltd.) Magnetic field strength: 400 MHz Detector: 3.2 mm auto MAS probe Solid-state NMR sample tube diameter: 3.2 mm Observation nucleus: ３１ P Observation frequency: 161.835 MHz Measurement temperature: room temperature Pulse sequence: single pulse 90° pulse length: 3.4 μs Flip angle: 45° Number of FID acquisition points: 1,024 points Waiting time after FID measurement until next pulse application: 1,500 s MAS (magic angle spinning) rotation speed: 14 kHz Number of accumulations: 64 Measurement range: 400 ppm to -300 ppm External standard: NH ４ H ２ P.O. ４ (chemical shift 1.00 ppm)

[0089] solid ３１ The data processing conditions for the P-NMR measurements were an exponential function as the window function, and a value within the range in which the half-width of the peak did not change significantly was used as the line broadening value, depending on the signal-to-noise ratio of each sample. The actual values ​​of the line broadening values ​​are described in the Examples and Comparative Examples. Backward linear prediction was not used.

[0090] When peak separation is required, the obtained solid ３１ The P-NMR spectrum was analyzed to determine the separated peaks. ３１From each NMR peak (experimental value) on the P-NMR spectrum, peak separation was performed using the nonlinear least squares method and a Gaussian function to calculate the separated peaks, and the calculated values ​​of the NMR peaks and the residual sum of squares R2 were calculated. ３１ The following documents 1 to 3 were referenced for the assignment of each peak obtained by waveform separation of the P-NMR spectrum. Document 1: Christian Dietrich et al. J. Mater. Chem. A, 2017, 5, 18111-18119. Document 2: Japanese Patent No. 6719037 Document 3: Japanese Patent No. 7297911 Document 4: JP 2021-122029

[0091] For example, as disclosed in Reference 1, the peak obtained by waveform separation around 125 ppm is PS ３ － As disclosed in Reference 2, the peak at around 106 ppm was assigned to P ２ S ６ ４－ The peaks around 92 ppm and 78 ppm were attributed to thiolicon region II type crystals, and the peak around 84 ppm was attributed to low ion-conducting crystals. As disclosed in Reference 3, the peak around 50 to 60 ppm was attributed to P ２ S ５ In addition, P in this attribution ２ S ５ Generally, the main component of diphosphorus pentasulfide is P ４ S １０ Skeleton and P ４ S ９ As disclosed in Reference 4, the peak at around 86 ppm is β-Li. ３ P.S. ４ As a peak that cannot be assigned in References 1 to 4, a peak of unknown assignment was observed at 145 ppm in Example 1.

[0092] solid ３１The composition calculation of each component obtained by waveform separation of the P-NMR spectrum was carried out by using the area value of the separated peak as a percentage to calculate the proportion of each component shown below. Spinning sideband peaks were not used in calculating the composition of each component. The area ratio (%) of each peak to the total area of ​​the eight peaks shown in Table 2 was calculated. The results are shown in Table 2. ３１ The results of waveform separation of the P-NMR spectrum are shown in FIG. 12 (line broadening value 100 Hz) and FIG. 13 (line broadening value 100 Hz).

[0093]

[0094] From Table 2, P ２ S ５ In a molten state, the resulting cathode composite material is mixed with the S-C composite, and the composition of the resulting cathode composite material is P ２ S ５ is less than that of the comparative example, and conversely, P ２ S ６ ４－ and P.S. ３ － It was confirmed that the melted P ２ S ５ The component reacts partially with sulfur in the S-C complex, for example, inside or near the surface of the activated carbon, to form P ２ S ６ ４－ , P.S. ３ － This is because the melted P ２ S ５ This indicates that the molten P covers the S-C composite and forms a strong interface. ２ S ５ coated the S-C composite and formed a strong interface, resulting in P ２ S ５ becomes equal to or less than a certain value (for example, 25%), and P ２ S ６ ４－ and P.S. ３ － It is considered that the total value of the percentages is equal to or greater than a certain value (for example, 20%).

[0095] (3) Specific Surface Area Parameter The BET specific surface areas of the positive electrode composite and the solid electrolyte were measured using a specific surface area and pore distribution analyzer (Autosorb-3) manufactured by Quantacrome. The specific surface area parameter was calculated using the following formula: Specific surface area parameter = (specific surface area of ​​positive electrode composite) / (specific surface area of ​​solid electrolyte). ａ (In the formula, a is the mass ratio of the solid electrolyte to the entire positive electrode composite (mass of solid electrolyte / mass of the entire positive electrode composite). The specific surface area parameter corrects for the effect of the specific surface area of ​​the solid electrolyte and allows the difference between the presence and absence of melt treatment of the ionic conductor to be evaluated. The results are shown in Table 3.

[0096]

[0097] In the examples and comparative examples, the positive electrode composite precursor and the solid electrolyte were mixed with a weak force (using a rolling mill) to maintain the crystallinity of the solid electrolyte and suppress amorphization. The specific surface area parameter can be used to correct the effect of the specific surface area of ​​the solid electrolyte and evaluate the difference between the presence and absence of melting treatment. Comparing the specific surface area parameters, the values ​​of the comparative examples are higher than those of the examples. This is because, like the precursor, the P in which the S-C composite was melted ２ S ５ This suggests that the material is coated with

[0098] (4) Crystallinity Evaluation by X-ray Diffraction Measurement (XRD) The positive electrode composite precursor powder was filled into a groove with a diameter of 20 mm and a depth of 0.2 mm and leveled with glass to prepare a sample. This sample was sealed with a Kapton film for XRD and measured without being exposed to air. The XRD measurement was performed using a powder X-ray diffraction measurement device D2 PHASER manufactured by BRUKER Co., Ltd. under the following measurement conditions.

[0099] Tube voltage: 30 kV Tube current: 10 mA X-ray wavelength: Cu-Kα ray (1.5418 Å) Optical system: Concentration method Slit configuration: Soller slit 4° (both incident and receiving sides), divergence slit 1 mm, Kβ filter (Ni plate 0.5%), air scatter screen 3 mm) Detector: Semiconductor detector Measurement range: 2θ = 10-60 deg Step width, scan speed: 0.05 deg, 0.05 deg / sec

[0100] The presence or absence of a crystalline peak in the obtained spectrum confirmed the crystallinity of the sample. ２ S ５ Since the crystal peaks are at positions such as "2θ = 10.81°, 12.12°, 14.90°, 16.07°, 21.68°, 25.67°, and 30.33°," it was confirmed whether the crystal peaks were maintained at these positions in the positive electrode composite state. The results are shown in Table 3. X-ray diffraction charts of Examples 1 to 4 and Comparative Examples 2 and 3 are shown in Figures 14 to 19.

[0101] From Table 3, in the example, P ２ S ５ It can be seen that no diffraction peaks originating from crystals of P are observed. ２ S ５ It is expected that the crystallinity of disappears upon melting, and the amorphous phase remains around the SC composite, forming a strong interface.

[0102] [All-solid-state lithium-ion battery] All-solid-state lithium-ion batteries were fabricated using the positive electrode composites fabricated in the examples and comparative examples as described below, and the battery characteristics (charge and discharge characteristics) were evaluated. - Fabrication of negative electrode composite Lithium titanate ("LT-112" manufactured by Ishihara Sangyo Kaisha), a conductive additive ("Li-100" manufactured by Denka Co., Ltd., powdered acetylene black), and solid electrolyte C were mixed in a mortar in a mass ratio of 60:5:35 for 5 minutes to obtain a negative electrode composite (also referred to as "LTO (lithium titanate) negative electrode composite").

[0103] - Preparation of Lithium-ion Battery 100 mg of solid electrolyte A was placed in a 10 mm diameter Macol cylinder and pressure molded to form a solid electrolyte layer (layer of solid electrolyte A). Next, 10 mg of positive electrode composite powder was placed on one pressure surface of the solid electrolyte layer and pressure molded again. Next, 166 mg of LTO negative electrode composite was placed on the other pressure surface of the solid electrolyte layer (the pressure surface opposite the positive electrode) and pressure was applied. A Li foil with a diameter of 9 mm and a thickness of 0.1 mm was placed on top of it and pressure was applied again to prepare a lithium-ion battery.

[0104] Charge / Discharge Test A constant current charge / discharge test was performed on the lithium ion batteries using the positive electrode composites of each Example and Comparative Example. The voltage range for the constant current charge / discharge test was set to -0.4 to 1.3 V, and the current value was set as shown in Table 6 at a C rate determined based on the theoretical capacity of sulfur of 1672 mAh / g. The test was performed. For charging, CC-CV charging was performed, in which constant voltage charging was performed with a termination condition of 0.02 C after constant current charging, and for discharging, constant current discharge (CC discharge) was performed. The results are shown in Table 7.

[0105]

[0106]

[0107] It was confirmed that the Examples had higher discharge capacities at both low and high rates than the Comparative Examples. ２ S ５ The improvement in charge-discharge characteristics was confirmed in the examples in which a cathode composite precursor was prepared by melting an ion conductor (a cathode composite precursor). It is believed that the excellent charge-discharge characteristics were obtained in the examples by using a cathode composite precursor having a strong interface and a good ion conduction path.

[0108] The positive electrode composite of the present invention is suitable as a structural material for lithium ion batteries. Furthermore, lithium ion batteries containing the positive electrode composite of the present invention are suitable for use in, for example, information-related devices and communication devices such as personal computers, video cameras, and mobile phones, and vehicles such as electric vehicles.

[0109] 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 references cited in this specification and the applications from which this application claims priority under the Paris Convention are incorporated by reference in their entirety. In this specification, "x to y" represents a numerical range of "greater than or equal to x and less than or equal to y." The upper and lower limits of numerical ranges can be arbitrarily combined. Furthermore, two or more of the individual embodiments of the present invention that are not mutually exclusive can be combined, and an embodiment combining two or more embodiments is also an embodiment of the present invention.

Claims

1. A positive electrode composite material comprising a sulfur-based active material, a carbon material having pores, at least one of an ion conductor containing a phosphorus element and a modified body of the ion conductor, and a solid electrolyte, and satisfying at least one of the following formulas (1) and (2) in the P2p spectrum in surface element analysis by X-ray photoelectron spectroscopy. I Ａ / I Ｂ > 0.50 (1) I Ｃ / I Ｂ > 1.20 (2) (In the formula, I Ａ is the signal intensity at position A where the binding energy is around 135.4 eV, I Ｂ is the signal intensity at position B where the binding energy is around 134.25 eV, and I Ｃ is the signal intensity at position C where the binding energy is around 133.0 eV.) 2. The I Ｃ / I Ｂ is greater than 1.

3. The positive electrode composite material according to claim 1.

3. The cathode composite material according to claim 1 or 2, wherein the change rate of the element ratio C / P of carbon element and phosphorus element by surface element analysis using X-ray photoelectron spectroscopy before and after the Ar sputtering treatment is 0.550 or more.

4. The cathode composite material according to claim 3, wherein the change rate of the element ratio C / P is 0.600 or more.

5. Solid ３１ In the P-NMR measurement, P ２ S ６ ４－ The sum of the peak of and PS ３ － The positive electrode composite material according to any one of claims 1 to 4, wherein the total area of the peaks is 20% or more of the whole.

6. Solid ３１ In the P-NMR measurement, P ２ S ５ The positive electrode composite material according to any one of claims 1 to 5, wherein the area of the peak of is 25% or less of the whole.

7. The cathode composite material according to any one of claims 1 to 6, wherein the melting point of the ion conductor is 130°C to 450°C.

8. The cathode composite material according to any one of claims 1 to 7, wherein the ion conductor includes a lithium ion conductive material containing phosphorus element and one or more elements selected from lithium, boron, sulfur and oxygen, or a precursor thereof.

9. The cathode composite material according to any one of claims 1 to 8, wherein the ion conductor contains phosphorus sulfide.

10. The cathode composite material according to any one of claims 1 to 9, wherein the ion conductor contains diphosphorus pentasulfide.

11. The cathode composite material according to any one of claims 1 to 10, wherein the sulfur-based active material contains elemental sulfur.

12. The cathode composite material according to any one of claims 1 to 11, wherein the total mass ratio of the sulfur-based active material, the ion conductor containing phosphorus element and the modified product of the ion conductor to the carbon material is less than 5.

00.

13. A method for manufacturing a cathode composite material, comprising mixing at least one of a composite and a mixture of a sulfur-based active material and a carbon material having pores with a molten ion conductor to prepare a cathode composite material precursor, and mixing and pulverizing the cathode composite material precursor and a crystalline solid electrolyte under conditions where the crystallinity of the solid electrolyte does not disappear to produce a cathode composite material.

14. The manufacturing method according to claim 13, wherein a composite of the sulfur-based active material and the carbon material having pores is mixed with the molten ion conductor.

15. The manufacturing method according to claim 13 or 14, wherein the melting point of the ion conductor is 130°C to 450°C.

16. The manufacturing method according to any one of claims 13 to 15, wherein the ion conductor includes a lithium ion conductive material containing phosphorus element and one or more elements selected from lithium, boron, sulfur and oxygen, or a precursor thereof.

17. The manufacturing method according to any one of claims 13 to 16, wherein the ion conductor is phosphorus sulfide.

18. The manufacturing method according to any one of claims 13 to 17, wherein the ion conductor contains diphosphorus pentasulfide.

19. The manufacturing method according to any one of claims 13 to 18, wherein the sulfur-based active material contains elemental sulfur.

20. The manufacturing method according to any one of claims 13 to 19, wherein the mass ratio of the sulfur-based active material, the carbon material, and the ion conductor satisfies the following relationship: (sulfur-based active material + carbon material): ion conductor = 50:1 to 80 21. The manufacturing method according to any one of claims 13 to 20, wherein the total mass ratio of the sulfur-based active material and the ion conductor to the carbon material is less than 5.00 22. A positive electrode including the positive electrode composite material according to any one of claims 1 to 12 23. A lithium-ion battery including the positive electrode composite material according to any one of claims 1 to 12 or the positive electrode according to claim 22

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