Positive electrode composite material, manufacturing method of positive electrode composite material and lithium ion battery

Abstract

A positive electrode composite material comprising: a titanium sulfide TiSx (2lt; xlt; 10) and / or a discharge product of the titanium sulfide; and a sulfide solid electrolyte having a diffraction peak in which 2 [theta] is 20.1 + / -0.4 DEG in X-ray diffraction using a CuK [alpha] ray.

Description

TECHNICAL FIELD

[0001] The present application relates to a positive electrode composite material, a method for producing a positive electrode composite material, and a lithium ion battery. BACKGROUND

[0002] In order to improve the energy density of a lithium ion battery, sulfur is being studied for use as a positive electrode active material. Since sulfur is insulating, a technology for imparting electronic conductivity by compounding with a metal sulfide is being studied. For example, as a positive electrode active material for a lithium secondary battery, titanium polysulfide (TiS x : 2 < x < 10) (Patent Document 1).

[0003] Further, titanium polysulfide is known to be compounded with a solid electrolyte in order to improve the lithium ion conductivity of a positive electrode. As a solid electrolyte to be compounded, a sulfide solid electrolyte is being studied (Patent Document 1 and Non-Patent Document 1). A sulfide solid electrolyte is softer than an oxide solid electrolyte, and thus by laminating an electrode layer and a solid electrolyte layer, an electrode-electrolyte interface having low resistance can be formed.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT DOCUMENT

[0006] Patent Document 1: Japanese Patent Application Publication No. 2014-093210

[0007] NON-PATENT DOCUMENT

[0008] Non-Patent Document 1: Solid State Ionics 262 (2014) 143-146 SUMMARY

[0009] A lithium ion battery using titanium polysulfide for a positive electrode is not necessarily large in discharge capacity, and further improvement is required.

[0010] An object of the present application is to provide a positive electrode composite material, and a lithium ion battery large in discharge capacity using titanium polysulfide.

[0011] The present inventors have found that by using a positive electrode composite material in which a specific glass-ceramic solid electrolyte is combined in titanium polysulfide, a lithium ion battery large in discharge capacity can be obtained, and thus completed the present application. By using a specific glass-ceramic solid electrolyte, a lithium ion battery large in discharge capacity can be obtained compared to a solid electrolyte having the same elemental composition and a solid electrolyte having the same degree of ionic conductivity.

[0012] According to the present application, the following positive electrode composite material and the like can be provided.

[0013] 1. A positive electrode composite material comprising: a titanium sulfide TiSx (0 < x < 10) and at least one of a discharge product of the titanium sulfide and a sulfide solid electrolyte. x (2 < x < 10) and at least one of a discharge product of the titanium sulfide and a sulfide solid electrolyte.

[0014] The sulfide solid electrolyte has a diffraction peak at 20.1 ± 0.4° in 2θ in X-ray diffraction using CuKα rays.

[0015] 2. The positive electrode composite material according to claim 1, wherein the sulfide solid electrolyte contains lithium, phosphorus, sulfur, and a halogen as constituent elements.

[0016] 3. The positive electrode composite material according to claim 1 or 2, wherein the content ratio of lithium with respect to all the constituent elements of the sulfide solid electrolyte is 35 to 45 mol%.

[0017] 4. The positive electrode composite material according to any one of claims 1 to 3, wherein the content ratio a of the titanium sulfide, the content ratio b of the sulfide solid electrolyte, and the content ratio c of the conductive aid satisfy the following formulae (1) to (3).

[0018] 10 mass% ≤ a ≤ 90 mass% (1)

[0019] 0 mass% < b ≤ 65 mass% (2)

[0020] 0 mass% ≤ c ≤ 40 mass% (3)

[0021] (a + b + c = 100 mass%.)

[0022] 5. The positive electrode composite material according to any one of claims 1 to 4, which has a diffraction peak at 20.1 ± 0.4° in 2θ, a diffraction peak at 34 ± 1° in 2θ, and

[0023] one or more diffraction peaks selected from 15.5 ± 1°, 44 ± 1°, and 54 ± 1° in 2θ in X-ray diffraction using CuKα rays.

[0024]

[0025] 6. The positive electrode composite material according to claim 4, wherein the content ratio c of the conductive aid is 0 mass%.

[0026] 7. A method for producing a positive electrode composite material, comprising a step of mixing a titanium sulfide TiSx (0 < x < 10) satisfying the following (A) with a sulfide solid electrolyte satisfying the following (B). x (2 < x < 10) and a sulfide solid electrolyte satisfying the following (B).

[0027] (A) has a diffraction peak at 34 ± 1° in 2θ, and one or more diffraction peaks selected from 15.5 ± 1°, 44 ± 1°, and 54 ± 1° in 2θ in X-ray diffraction using CuKα rays. ​

[0028] (B) In X-ray diffraction using CuKα rays, a diffraction peak at 20.1 ± 0.4° in 2Θ.

[0029] 8. The production method according to 7, wherein the average particle diameter of the sulfide solid electrolyte is 10 μm or less.

[0030] 9. The production method according to 7 or 8, comprising a step of synthesizing the titanium sulfide by mechanically mixing sulfur and titanium disulfide.

[0031] 10. A positive electrode composite obtained by the production method according to any one of 7 to 9.

[0032] 11. A positive electrode comprising the positive electrode composite according to any one of 1 to 6 and 10.

[0033] 12. A lithium ion battery comprising the positive electrode according to 11.

[0034] According to the present application, it is possible to provide a positive electrode composite, and a lithium ion battery having a large discharge capacity using titanium polysulfide. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 are X-ray diffraction (XRD) patterns of the sulfide solid electrolyte powder A, the positive electrode composite of Example 1, the sulfide solid electrolyte powder C, and the positive electrode composite of Comparative Example 2.

[0036] Figure 2 are XRD patterns of the sulfide solid electrolyte powder B and the positive electrode composite produced in Comparative Example 1.

[0037] Figure 3 is an XRD pattern of the positive electrode composite produced in Example 2.

[0038] Figure 4 are XRD patterns of sulfur, titanium disulfide, the positive electrode active material B, and the positive electrode active material C.

[0039] Figure 5 is an XRD pattern of the sulfide solid electrolyte powder D.

[0040] Figure 6 is an XRD pattern of the positive electrode composite produced in Example 3.

[0041] Figure 7 is an XRD pattern of the positive electrode composite produced in Example 4.

[0042] Figure 8 are XRD patterns of the positive electrode composites produced in Examples 5 to 7. DETAILED DESCRIPTION

[0043] Hereinafter, embodiments of the present invention (hereinafter sometimes referred to as "the present embodiment") will be described. In addition, in this specification, the upper and lower limit values of the numerical ranges of "above", "below", and "~" are numerical values that can be arbitrarily combined. In addition, the numerical values of the examples can also be used as the upper and lower limit values.

[0044] 1. Positive electrode composite material

[0045] The positive electrode composite material of an embodiment of the present invention includes: titanium sulfide TiS x (2 < x < 10) and at least one of the discharge products of the titanium sulfide (hereinafter, sometimes collectively referred to as polysulfide titanium for the titanium sulfide and its discharge products); a sulfide solid electrolyte having a diffraction peak with 2θ of 20.1 ± 0.4° in X-ray diffraction using CuKα radiation.

[0046] The above sulfide solid electrolyte is a glass-ceramic having a peak at a specified position in powder X-ray diffraction (XRD) measurement. By using this sulfide solid electrolyte in combination with polysulfide titanium, a positive electrode composite material for a lithium-ion battery with a large discharge capacity can be obtained.

[0047] Hereinafter, the constituent components of the positive electrode composite material of the present embodiment will be described.

[0048] [Sulfide solid electrolyte]

[0049] The sulfide solid electrolyte used in the present embodiment is a glass-ceramic having a diffraction peak with 2θ of 20.1 ± 0.4° in XRD measurement. In this application, the glass-ceramic solid electrolyte refers to a solid electrolyte in which a peak derived from the solid electrolyte is observed in XRD measurement, and is a material regardless of whether there is a peak derived from the raw material of the solid electrolyte. That is, the glass-ceramic solid electrolyte includes the crystal structure derived from the solid electrolyte, and part or all of it can be the crystal structure derived from the solid electrolyte. And as long as the glass-ceramic solid electrolyte has the above X-ray diffraction pattern, it may also contain an amorphous component (also referred to as "glass component") in a part thereof. In addition, the glass-ceramic solid electrolyte includes a so-called glass-ceramic obtained by heating an amorphous solid electrolyte (glass component) above the crystallization temperature.

[0050] In this embodiment, the peak originating from the solid electrolyte is the diffraction peak with 2θ of 20.1 ± 0.4°. Furthermore, diffraction peaks with 2θ = 23.5 ± 0.4°, 37.1 ± 0.8°, and 40.7 ± 0.8° can also be used as peaks originating from the solid electrolyte for determining the sulfide solid electrolyte. Alternatively, it is not necessary to observe all the aforementioned peaks; the peak with 2θ = 20.1 ± 0.4° and at least one other peak can be used for determination.

[0051] In one embodiment, the sulfide solid electrolyte comprises lithium, phosphorus, sulfur, and halogen as constituent elements. The halogen (X) preferably comprises one or more selected from fluorine (F), chlorine (Cl), bromine (Br), and iodine (I), more preferably Br or I. Furthermore, the halogen (X) preferably comprises I.

[0052] The types and molar ratios of constituent elements in sulfide solid electrolytes can be confirmed, for example, by using an ICP-based luminescence spectrophotometer.

[0053] The molar ratio of the constituent elements in the sulfide solid electrolyte can be adjusted by controlling the blending of raw materials. Furthermore, the molar ratio of the constituent elements in the raw materials is approximately equal to the molar ratio of the constituent elements in the resulting sulfide solid electrolyte.

[0054] The sulfide solid electrolyte of this embodiment can be manufactured, for example, by mixing and pulverizing the starting materials of a known lithium-ion sulfide solid electrolyte in such a way that the molar ratio of the constituent elements meets a specified range, vitrifying them, and then further ceramicizing the resulting material by heat treatment.

[0055] As a raw material for sulfide solid electrolytes, two or more compounds or monomers containing lithium, phosphorus, sulfur and halogen as constituent elements can be used in combination. As long as the ionic conductivity caused by the contained metal atoms is exhibited, they can be used without particular restrictions.

[0056] Examples of lithium-containing raw materials include lithium compounds such as lithium sulfide (Li2S), lithium oxide (Li2O), and lithium carbonate (Li2CO3), as well as lithium metal monomers. Among these, lithium compounds are preferred, and lithium sulfide is more preferred.

[0057] The aforementioned lithium sulfide can be used without particular restrictions, with high-purity lithium sulfide being preferred. Lithium sulfide can be manufactured, for example, by the methods described in Japanese Patent Application Publication Nos. 7-330312, 9-283156, 2010-163356, and 2011-84438.

[0058] Specifically, lithium hydroxide is reacted with hydrogen sulfide in a hydrocarbon organic solvent at 70°C to 300°C to generate lithium hydrogen sulfide, and then the reaction solution is desulfurized and hydrogenated to synthesize lithium sulfide (Japanese Patent Application Publication No. 2010-163356).

[0059] In addition, lithium hydroxide and hydrogen sulfide are reacted in an aqueous solvent at 10°C to 100°C to generate lithium hydrogen sulfide, and then the reaction solution is desulfurized and hydrogenated to synthesize lithium sulfide (Japanese Patent Application Publication No. 2011-84438).

[0060] Examples of phosphorus (P)-containing raw materials include phosphorus sulfides such as phosphorus trisulfide (P2S3) and phosphorus pentasulfide (P2S5), phosphorus compounds such as sodium phosphate (Na3PO4), and phosphorus monomers. Among these, phosphorus sulfides are preferred, and phosphorus pentasulfide (P2S5) is more preferred. Phosphorus compounds such as phosphorus pentasulfide (P2S5) and phosphorus monomers can be used without particular limitation as long as they are industrially manufactured and sold.

[0061] As a raw material containing halogen (X), it is preferred to contain, for example, a halogen compound represented by the following formula.

[0062] M l -X m

[0063] In the formula, M represents sodium (Na), lithium (Li), boron (B), aluminum (Al), silicon (Si), phosphorus (P), sulfur (S), germanium (Ge), arsenic (As), selenium (Se), tin (Sn), antimony (Sb), tellurium (Te), lead (Pb), bismuth (Bi), or a substance bonded with oxygen or sulfur elements to these elements, preferably lithium (Li) or phosphorus (P), more preferably lithium (Li).

[0064] X is a halogen element selected from fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).

[0065] Furthermore, l is an integer of 1 or 2, and m is an integer from 1 to 10. When m is an integer from 2 to 10, that is, when there are multiple X, X can be the same or different. For example, in SiBrCl3 (described later), m is 4, and X is composed of different elements such as Br and Cl.

[0066] Specifically, examples of halogen compounds represented by the above formulas include sodium halides such as NaI, NaF, NaCl, and NaBr; lithium halides such as LiF, LiCl, LiBr, and LiI; boron halides such as BCl3, BBr3, and BI3; aluminum halides such as AlF3, AlBr3, AlI3, and AlCl3; silicon halides such as SiF4, SiCl4, SiCl3, Si2Cl6, SiBr4, SiBrCl3, SiBr2Cl2, and SiI4; phosphorus halides such as PF3, PF5, PCl3, PCl5, POCl3, PBr3, POBr3, PI3, P2Cl4, and P2I4; and SF2, SF4, SF6, and S2F2. 10 Sulfur halides such as SCl2, S2Cl2, S2Br2; Germanium halides such as GeF4, GeCl4, GeBr4, GeI4, GeF2, GeCl2, GeBr2, GeI2; Arsenic halides such as AsF3, AsCl3, AsBr3, AsI3, AsF5; Selenium halides such as SeF4, SeF6, SeCl2, SeCl4, Se2Br2, SeBr4; Tin halides such as SnF4, SnCl4, SnBr4, SnI4, SnF2, SnCl2, SnBr2, SnI2; Antimony halides such as SbF3, SbCl3, SbBr3, SbI3, SbF5, SbCl5; TeF4, Te2F 10 Tellurium halides such as TeF6, TeCl2, TeCl4, TeBr2, TeBr4, and TeI4; lead halides such as PbF4, PbCl4, PbF2, PbCl2, PbBr2, and PbI2; and bismuth halides such as BiF3, BiCl3, BiBr3, and BiI3.

[0067] Examples of lithium halides include lithium chloride (LiCl), lithium bromide (LiBr), lithium iodide (LiI), phosphorus pentachloride (PCl5), phosphorus trichloride (PCl3), phosphorus pentabromide (PBr5), and phosphorus tribromide (PBr3). LiCl, LiBr, and LiI are preferred, as is PBr3; LiCl, LiBr, and LiI are even more preferred; and LiI and LiBr are even more preferred.

[0068] A halogen compound may be used alone or in combination of two or more of the above compounds. That is, at least one of the above compounds may be used.

[0069] In this embodiment, the raw materials preferably include lithium compounds, phosphorus compounds and one or more halogen compounds, and at least one of the lithium compounds and phosphorus compounds contains sulfur, more preferably a combination of lithium sulfide, phosphorus sulfide and one or more lithium halides.

[0070] For example, when using lithium sulfide, phosphorus pentasulfide, or lithium halide as raw materials for sulfide solid electrolytes, the molar ratio of lithium sulfide to phosphorus pentasulfide in the input raw materials is preferably 65-85:15-35, more preferably 70-80:20-30, even more preferably 72-78:22-28, and particularly preferably 75:25.

[0071] Furthermore, when the sulfide solid electrolyte uses Li2S, P2S5 and LiX as raw materials, the total content of lithium sulfide and phosphorus pentasulfide ([Li2S+P2S5]×100 / [Li2S+P2S5+LiX]) is preferably 60 to 95 mol%, more preferably 65 to 90 mol%, and even more preferably 70 to 85 mol%.

[0072] In one embodiment, the lithium content relative to all constituent elements of the sulfide solid electrolyte is 35 to 45 mol%. For example, even if the lithium content is lower than that of a solid electrolyte having a sulfide-germanium ore-type crystal structure, it still becomes a positive electrode composite material for obtaining a battery with a large discharge capacity.

[0073] In this embodiment, mechanical stress is applied to the above-mentioned raw materials to cause them to react and produce an intermediate (glassy powder). Here, "applying mechanical stress" refers to mechanically applying shear force, impact force, etc. Examples of means of applying mechanical stress include pulverizers such as star ball mills, vibratory mills, and rolling mills, as well as kneaders. Through strong mechanical stress, at least a portion of the raw material powder is pulverized and mixed to a state where it can no longer maintain its crystallinity.

[0074] As for the conditions for pulverizing and mixing, for example, when using a planetary ball mill as the pulverizer, the rotational speed can be set to tens to hundreds of revolutions per minute, and the processing time to 0.5 hours to 100 hours. More specifically, in the case of the planetary ball mill (Fritsch model P-7) used in the embodiments of this application, the rotational speed of the planetary ball mill is preferably 100 rpm to 500 rpm, more preferably 150 rpm to 450 rpm.

[0075] The spheres used as the pulverizing medium, for example when using zirconia spheres, preferably have a diameter of 0.2 to 20 mm.

[0076] The temperature during pulverization is not specifically specified, but it is preferably below 200°C to prevent the solid electrolyte from crystallizing and solidifying.

[0077] The intermediate prepared by pulverization and mixing was subjected to heat treatment. Specifically, regarding the heating temperature of the intermediate, differential thermal-thermal-gravimetric analysis (TGDTA) was performed on the intermediate at a heating rate of 10°C / min, with the temperature (T0) being the temperature at the peak of the exothermic peak observed at the lowest temperature side. c1 Starting from 5°C, it is preferably set to below 5°C, more preferably below 10°C, and even more preferably below 15°C. There is no particular limitation on the lower limit; it can be set to approximately 10°C or more above the temperature of the peak of the exothermic peak observed at the lowest temperature. By setting such a temperature range, the sulfide solid electrolyte (glass-ceramic solid electrolyte) used in this embodiment can be obtained more effectively.

[0078] The heating temperature for obtaining the glass-ceramic solid electrolyte of this embodiment cannot be specified in general, but it is generally preferred to be 250°C or less, more preferably 225°C or less, and even more preferably 200°C or less. There is no particular limitation on the lower limit, but it is preferred to be 100°C or more, more preferably 110°C or more, and even more preferably 120°C or more.

[0079] The heating time is not particularly limited as long as it is sufficient to obtain the desired glass-ceramic solid electrolyte. For example, it is preferably 10 minutes or more, more preferably 30 minutes or more, further preferably 60 minutes or more, and even more preferably 2 hours or more. In addition, there is no particular upper limit to the heating time, but it is preferably 10 hours or less, more preferably 8 hours or less, further preferably 6 hours or less, and even more preferably 4 hours or less.

[0080] The atmosphere for heat treatment is not particularly limited; it can be under a stream of hydrogen sulfide, an inert gas atmosphere such as nitrogen or argon, or a vacuum atmosphere.

[0081] Titanium sulfide (TiS) x (2 <x<10)]

[0082] There are no particular limitations on the titanium sulfide, and any known titanium sulfide can be used. Specifically, the titanium sulfide disclosed in Patent Document 1, which is manufactured by mixing and pulverizing crystalline TiS2 and sulfur as raw materials through mechanical grinding, can be cited as an example.

[0083] In one embodiment, the titanium sulfide is either amorphous or crystalline. Crystalline titanium sulfides exhibit a diffraction peak at 2θ of 34 ± 1° and one or more diffraction peaks selected from 2θ values ​​of 15.5 ± 1°, 44 ± 1°, and 54 ± 1° in X-ray diffraction using CuKα rays.

[0084] The aforementioned diffraction peaks originate from titanium disulfide crystals and are based on diffraction peaks with a diffraction angle of 2θ = 15.5 ± 1° on the (001) plane of TiS2 crystal, 2θ = 34 ± 1° on the (011) plane, 2θ = 44 ± 1° on the (102) plane, and 2θ = 54 ± 1° on the (110) plane. The synthesis of titanium sulfides will be described later.

[0085] Titanium sulfides are partially or completely converted into discharge products during battery reactions. Therefore, in the positive electrode composite material (positive electrode) of one embodiment, discharge products of titanium sulfides are present.

[0086] Examples of discharge products of titanium sulfides include substances containing Li, obtained by lithiation of titanium sulfides.

[0087] [other]

[0088] In one embodiment of the present invention, the cathode composite material preferably further comprises a conductive additive.

[0089] The conductive additive can be any material with electronic conductivity. Preferably, the conductive additive has a high specific surface area and multiple fine pores. Particularly preferred are porous carbon materials. Carbon materials have high conductivity and are lighter than other conductive materials, thus increasing the battery's output density and capacity per unit weight.

[0090] The specific surface area of ​​the conductive additive is preferably 0.1 m². 2 / g or more 5000m 2 / g or less, preferably 1m 2 / g or more 4000m 2 / g or less, more preferably 1m 2 / g or more 3000m 2 / g or less, the most preferred is 10m 2 / g or more 3000m 2 / g or less.

[0091] The pore volume of the conductive additive is preferably 0.1cc / g or more and 5.0cc / g or less.

[0092] The average diameter of the pores in the conductive additive is preferably 0.1 nm to 40 nm, more preferably 0.5 nm to 40 nm, even more preferably 0.5 nm to 20 nm, and most preferably 1 nm to 20 nm.

[0093] The specific surface area, pore volume, and pore diameter of the conductive additive can be determined using the nitrogen adsorption isotherm obtained by adsorbing nitrogen on the conductive additive at the temperature of liquid nitrogen. Specifically, the specific surface area can be calculated using the nitrogen adsorption isotherm by the Brunauer-Emmett-Teller (BET) multi-point method. In addition, the pore volume and pore diameter can be determined using the nitrogen adsorption isotherm by the Barrett-Joyner-Halenda (BJH) method.

[0094] As a measuring device, for example, a specific surface area and pore distribution measuring device (Autosorb-3) manufactured by Quantachrome Corporation can be used for measurement.

[0095] The carbon material is not particularly limited, and examples include carbon blacks such as Ketjen black, acetylene black, super conductive acetylene black (Denka Black), thermal cracking carbon black, and channel black, mesoporous carbon, activated carbon, amorphous carbon, carbon nanotubes, vapor grown carbon fiber (VGCF), carbon nano-horns, etc. As the conductive carbon material, examples include fullerenes, carbon fibers, natural graphite, artificial graphite, graphene, graphene oxide, reduced graphene oxide, etc. Among them, activated carbon is preferred. In addition, these can be used alone or in combination of two or more. In addition, composites of these can also be used.

[0096] In one embodiment, it is preferred that the content a of titanium sulfide, the content b of the sulfide solid electrolyte, and the content c of the conductive additive in the positive electrode composite material satisfy the following formulas (1) to (3).

[0097] 10% by mass ≤ a ≤ 90% by mass (1)

[0098] 0% by mass < b ≤ 65% by mass (2)

[0099] 0% by mass ≤ c ≤ 40% by mass (3)

[0100] (a + b + c is 100% by mass.)

[0101] By satisfying formulas (1) to (3), a battery with a larger discharge capacity can be obtained. The content a of titanium sulfide is more preferably 30% by mass or more, and further preferably 60% by mass or more. In addition, it is more preferably 85% by mass or less.

[0102] The content b of the sulfide solid electrolyte is more preferably 10% by mass or more, and further preferably 15% by mass or more. In addition, it is more preferably 50% by mass or less.

[0103] The content ratio c of the conductive additive is more preferably 30% by mass or less, and further preferably 10% by mass or less. In addition, it may be 0% by mass. That is, a high-performance positive electrode composite material can be obtained even without using a conductive additive.

[0104] In one embodiment, the positive electrode composite material may contain other components in addition to the above-mentioned titanium polysulfide, sulfide solid electrolyte, and conductive additive, or may not contain other components. The other components are not particularly limited, and examples thereof include a binder, a solvent, and a dispersant.

[0105] The positive electrode composite material of the present embodiment can be manufactured by the method described below.

[0106] 2. Method for manufacturing positive electrode composite material

[0107] The method for manufacturing the positive electrode composite material according to one embodiment of the present invention includes a step of mixing titanium sulfide TiS satisfying the following (A) x (2 < x < 10) with a sulfide solid electrolyte satisfying the following (B).

[0108] (A) In X-ray diffraction using CuKα radiation, it has a diffraction peak at 2θ of 34 ± 1°, and one or more diffraction peaks selected from 2θ of 15.5 ± 1°, 44 ± 1°, and 54 ± 1°.

[0109] (B) In X-ray diffraction using CuKα radiation, it has a diffraction peak at 2θ of 20.1 ± 0.4°.

[0110] As described above, the above (A) means that the titanium sulfide contains titanium disulfide crystals. The above (B) means that the sulfide solid electrolyte is a specified glass ceramic. In the present embodiment, by mixing the above-mentioned titanium sulfide and sulfide solid electrolyte, a positive electrode composite material for a lithium-ion battery with a large discharge capacity can be manufactured.

[0111] In one embodiment, it includes a step of mechanically mixing sulfur and titanium disulfide (TiS2) to synthesize the above-mentioned titanium sulfide.

[0112] TiS2 used as a raw material is not particularly limited, and any commercially available TiS2 can be used. It is particularly preferred to use high-purity TiS2.

[0113] There is no particular limitation on the sulfur used as a raw material, and any crystal system of sulfur can be used as long as it is solid at normal temperature and pressure.

[0114] The ratio of TiS2 to sulfur is set to the same ratio as the element ratio of titanium to sulfur in the target titanium polysulfide. TiS xThe x is preferably 3 or more or 4 or more, and preferably 9 or less or 8 or less. More preferably, it is mixed in such a manner that x of TiS x becomes 4 to 6.

[0115] The mechanical grinding method can be carried out, for example, by using mechanical comminution devices such as a ball mill, a rod mill, a vibration mill, a disk mill, a hammer mill, a jet mill, a VIS mill, etc. to mix and comminute raw materials.

[0116] In the mechanical grinding method, complete amorphization is not carried out, but it is processed to a state where a small amount of fine crystals of TiS2 remain. The crystal state of TiS2 can be confirmed by the position and half-width value of the diffraction peak based on XRD measurement.

[0117] In one embodiment, an active material-conductive additive composite material can be formed from the above titanium sulfide and a conductive additive, and then the sulfide solid electrolyte is mechanically mixed with the active material-conductive additive composite material.

[0118] In the present embodiment, the active material or the active material-conductive additive composite material is mechanically mixed with the sulfide solid electrolyte to form a positive electrode composite material. Through this process, a part of the active material, the active material-conductive additive composite material, and the sulfide solid electrolyte can be comminuted.

[0119] For example, in the case of a planetary ball mill (manufactured by Fritsch: model P-7), the rotational speed of the planetary ball mill is preferably 50 rpm or more and 500 rpm or less, and more preferably 80 rpm or more and 400 rpm or less.

[0120] As the balls for the grinding medium, for example, in the case of using zirconia balls, their diameter is preferably 0.2 to 20 mm.

[0121] In one embodiment, the average particle diameter of the sulfide solid electrolyte is 10 μm or less. Thereby, an ionic conduction path in the positive electrode can be sufficiently formed, and thus a battery with a large discharge capacity can be obtained. The average particle diameter is more preferably 6 μm or less, and particularly preferably 3 μm or less.

[0122] In addition, the average particle diameter means the median diameter (d50).

[0123] In one embodiment, it is preferably prepared in such a manner that the content rate a of titanium sulfide, the content rate b of the sulfide solid electrolyte, and the content rate c of the conductive additive in the positive electrode composite material satisfy the following formulas (1) to (3).

[0124] 10% by mass ≤ a ≤ 90% by mass (1)

[0125] 0% by mass < b ≤ 65% by mass (2)

[0126] 0% by mass ≤ c ≤ 40% by mass (3)

[0127] (a+b+c is 100% of mass).

[0128] By satisfying equations (1) to (3), a battery with a larger discharge capacity can be obtained.

[0129] 3. Positive electrode and lithium-ion battery

[0130] One embodiment of the present invention provides a positive electrode or lithium-ion battery comprising the above-described positive electrode composite material of the present invention. For example, by using a solid electrolyte instead of a liquid electrolyte, an all-solid-state lithium-ion battery can be manufactured. By using the positive electrode composite material of the present invention, an all-solid-state lithium-ion battery with a large discharge capacity can be produced.

[0131] All-solid-state lithium-ion batteries mainly consist of a positive electrode layer, a negative electrode layer, and an electrolyte layer. However, the positive electrode composite material of the present invention is suitable as a constituent material of the positive electrode layer. The negative electrode layer and the electrolyte layer can be manufactured by known methods. In addition to the positive electrode layer, the negative electrode layer, and the electrolyte layer, a current collector is preferably used, and a known current collector is used as the current collector.

[0132] There are no particular limitations on the solid electrolyte; any known solid electrolyte can be used.

[0133] Example

[0134] The present invention will now be described in detail based on embodiments. The present invention is not limited to these embodiments. The following illustrates the evaluation methods for the samples prepared in each example.

[0135] (1) Ionic conductivity

[0136] It is formed from a solid electrolyte into a shape with a diameter of 10 mm (cross-sectional area S: 0.785 cm²). 2 A sample was prepared from spherical particles with a height (L) of 0.1–0.3 cm. The top and bottom of the sample were used as electrode terminals, and measurements were taken at 25°C using AC impedance spectroscopy (frequency range: 1 MHz–1 Hz, amplitude: 10 mV) to obtain a Cole-Cole diagram. Near the right end of the arc observed in the high-frequency region, the real part Z'(Ω) at the point where -Z"(Ω) is minimum was taken as the volume resistance R(Ω) of the electrolyte, and the ionic conductivity σ(S / cm) was calculated according to the following formula.

[0137] R = ρ(L / S)

[0138] σ=1 / ρ

[0139] (2) X-ray diffraction (XRD) measurement

[0140] Powder XRD measurements were used to analyze the properties of the sample and the presence or absence of diffraction peaks. Samples without diffraction peaks, or with only peaks originating from the raw material, were identified as amorphous; samples with diffraction peaks from sources other than the raw material were identified as crystalline.

[0141] Specifically, the sample powder was filled into a groove with a diameter of 20 mm and a depth of 0.2 mm, and the sample was prepared by leveling it with glass. The sample was then measured using XRD with a Kapton film sealed to prevent contact with air.

[0142] XRD measurements were performed using a Bruker D2 PHASER powder X-ray diffraction measurement system under the following conditions.

[0143] [Measurement Conditions]

[0144] Tube voltage: 30kV

[0145] Tube current: 10mA

[0146] X-ray wavelength: Cu-Kα rays

[0147] Optical system: lumped method

[0148] Slit configuration: 4° Solar slit (same on the incident and receiving sides), 1mm diverging slit, Kβ filter (0.5% Ni plate), 3mm air scattering screen.

[0149] Detector: Semiconductor detector

[0150] Measurement range: 2θ = 10⁻⁶⁰ degrees

[0151] Step width and scan speed: 0.05 deg, 0.05 deg / second

[0152] (3) Average particle size

[0153] The median diameter (d50) of solid electrolyte powder was measured using a laser diffraction / scattering particle size distribution device (manufactured by Horiba Manufacturing Co., Ltd., LA-960).

[0154] Example 1

[0155] (1) Preparation of positive electrode active material powder (titanium sulfide)

[0156] In an argon-atmospheric glove box, titanium disulfide (TiS2) powder and sulfur (S) powder were weighed at a molar ratio of 1:2 and sealed together with 90g of zirconia balls with a diameter of 4mm in a 45mL zirconia container. The container was then mechanically ground at 510rpm for 50 hours using a planetary ball mill (FRITSCH P7 Classic Line) to obtain positive electrode active material powder A.

[0157] (2) Preparation of sulfide solid electrolytes

[0158] In an argon-atmospheric glove box, 0.4936 g of lithium sulfide, 0.7959 g of phosphorus pentasulfide, 0.2104 g of lithium iodide, and 10 zirconia balls with a diameter of 10 mm were sealed together in a 45 mL zirconia jar. The jar was mechanically ground at 370 rpm for 40 hours using a planetary ball mill (FRITSCH P7 Classic Line) to obtain a powder. The obtained powder was then heated at 195 °C for 3 hours to obtain sulfide solid electrolyte powder A (glass ceramic).

[0159] The ionic conductivity of sulfide solid electrolyte powder A is 3.8 mS / cm. -1 The average particle size d50 is 6 μm.

[0160] Figure 1 The XRD pattern of sulfide solid electrolyte powder A (electrolyte A) is shown. Peaks originating from the solid electrolyte were observed at 2θ = 20.1°, 23.5°, 37.2°, and 40.7°.

[0161] (3) Fabrication of positive electrode composite materials

[0162] Weigh the positive electrode active material powder A and acetylene black at a mass ratio of 50:50 and mix them in an agate mortar for 5 minutes. Seal the resulting powder together with 100 zirconia balls with a diameter of 5 mm into a 45 mL zirconia jar and mix them in a planetary ball mill (FRITSCH P7 Classic Line) at 370 rpm for 1 hour to obtain a composite of positive electrode active material and conductive additive.

[0163] Next, sulfide solid electrolyte powder A was added to the container in a mass ratio of 50:50 with the composite of positive electrode active material and conductive additive, and then mixed for 30 minutes at 100 rpm using a planetary ball mill to obtain the positive electrode composite material.

[0164] Figure 1 The XRD pattern of the positive electrode composite material (Example 1) is shown.

[0165] (4) All-solid-state lithium-ion batteries

[0166] As a method for manufacturing all-solid-state lithium-ion batteries, the working electrode uses a positive electrode composite material, with a sulfide-based solid electrolyte A used as the electrolyte layer and a lithium-indium alloy used as the counter electrode. The positive electrode composite material used in the working electrode is 5 mg.

[0167] Comparative Example 1

[0168] (1) Preparation of sulfide solid electrolytes

[0169] In an argon-atmospheric glove box, 4.1414 g of lithium sulfide, 4.1739 g of phosphorus pentasulfide, 1.7514 g of lithium chloride, and 40 zirconia balls with a diameter of 10 mm were sealed together in a 250 mL zirconia jar. The jar was then mechanically ground at 220 rpm for 40 hours using a planetary ball mill (FRITSCH P5 Classic Line).

[0170] The obtained powder was heated at 430°C for 2 hours. The result was pulverized in a mortar and then recovered through a sieve with an opening size of 100 μm. 2 g of the recovered powder, 18.2 g of toluene, and 34 g of zirconia balls with a diameter of 2 mm were sealed into a 45 mL zirconia jar. The jar was set in a planetary ball mill (FRITSCH P7 Classic Line) and pulverized at 150 rpm for 17 minutes to obtain a slurry. The obtained slurry was vacuum dried at 120°C for 2 hours to obtain sulfide solid electrolyte powder B.

[0171] The ionic conductivity of sulfide solid electrolyte powder B is 4.0 mS / cm. -1 The average particle size d50 is 6 μm.

[0172] Figure 2 The XRD pattern of sulfide solid electrolyte powder B (electrolyte B) is shown. The XRD results indicate that sulfide solid electrolyte powder B is a sulfide solid electrolyte of the argyrocerium sulfide type.

[0173] (2) Fabrication of positive electrode composite materials and all-solid-state lithium-ion batteries

[0174] Except for changing sulfide solid electrolyte A to sulfide solid electrolyte B, the positive electrode composite material and all-solid-state lithium-ion battery were fabricated in the same manner as in Example 1.

[0175] Figure 2 The XRD measurement results of the cathode composite material prepared in Comparative Example 1 are shown.

[0176] Comparative Example 2

[0177] (1) Preparation of sulfide solid electrolytes

[0178] In an argon-atmospheric glove box, 0.5742 g of lithium sulfide, 0.9258 g of phosphorus pentasulfide, and 10 zirconia balls with a diameter of 10 mm were sealed together in a 45 mL zirconia jar. The jar was then mechanically milled at 370 rpm for 40 hours in a ball mill (FRITSCH P7 Classic Line) to obtain sulfide solid electrolyte powder C.

[0179] The ionic conductivity of sulfide solid electrolyte powder C is 0.32 mS / cm. -1 The average particle size d50 is 6 μm.

[0180] Figure 1 The XRD pattern of sulfide solid electrolyte powder C (electrolyte C) is shown. The XRD measurements show that, apart from the peaks based on the raw material, there are no distinct diffraction peaks, thus confirming that sulfide solid electrolyte powder C is glass.

[0181] (2) Fabrication of positive electrode composite materials and all-solid-state lithium-ion batteries

[0182] Except for changing sulfide solid electrolyte A to sulfide solid electrolyte C, the positive electrode composite material and all-solid-state lithium-ion battery were fabricated in the same manner as in Example 1.

[0183] Figure 1 The XRD pattern of the positive electrode composite material (Comparative Example 2) is shown.

[0184] [Evaluation of Battery Characteristics]

[0185] The voltage range of the all-solid-state lithium-ion batteries fabricated in the examples and comparative examples was set to 0.9-2.4V vs. Li-In, and the current density was set to 0.064 mA / cm². -2 A constant current charge-discharge test was conducted on the all-solid-state battery.

[0186] The results are shown in Table 1. In the table, the composition of the cathode composite material (TiS) is... X SE:C) represents titanium sulfide: sulfide solid electrolyte: conductive additive (mass ratio).

[0187] [Table 1]

[0188]

[0189] In Comparative Example 1, sulfide solid electrolyte powder B (a sulfide-germanium sulfide solid electrolyte) with the same ionic conductivity as sulfide solid electrolyte powder A (glass-ceramic) used in Example 1 was used. Furthermore, in Comparative Example 2, sulfide solid electrolyte powder C (glass) with a similar proportion of Li atoms was used. As a result, it was confirmed that the all-solid-state lithium-ion battery of Example 1 exhibited a large discharge capacity per 1g of cathode composite material.

[0190] It is believed that sulfide solid electrolyte powder C (glass) has lower lithium-ion conductivity than sulfide solid electrolyte powder A (glass ceramic), and the lithium-ion conductivity resistance in the positive electrode composite material is larger, thus reducing the battery capacity.

[0191] On the other hand, although sulfide solid electrolyte powder B (silver-germanium sulfide solid electrolyte) has the same lithium-ion conductivity as the aforementioned glass ceramics, its capacity is smaller.

[0192] The main reason is believed to be related to titanium polysulfide (TiS). x The influence of the fragility of solid electrolyte particles during recombination and the proportion of Li element contained in the solid electrolyte.

[0193] Crystalline solid electrolytes with a sulforaphite-germanium type crystal structure consist solely of crystalline components. Therefore, if they are synthesized by reacting with TiS... x When stress is applied due to the composite formation of TiS, the impact is uniformly applied to the entire solid electrolyte particle, increasing the stress and causing the solid electrolyte particles to break down and become smaller. The resulting smaller particle size crystalline solid electrolyte with a sulforaphite-germanium-type crystal structure reacts with TiS... x During recombination, it comes into full contact with the TiS, thus increasing its reactivity and supplying lithium ions to TiS. x Furthermore, it is believed that a high proportion of Li in crystalline solid electrolytes with a sulforaphite-germanium-type crystal structure can easily lead to increased reactivity and a tendency to react with TiS. x The reduced lithium-ion conductivity due to insufficient lithium-ion supply leads to increased lithium-ion conductivity resistance within the cathode composite material, resulting in a smaller discharge capacity.

[0194] On the other hand, glass-ceramic solid electrolytes, due to their glass content, even with the interaction with TiS... x The stress is applied due to the composite structure, and the increase in stress is suppressed by the deformation of the glass composition, thus maintaining the particle size of the solid electrolyte. As a result, compared with crystalline solid electrolytes having a sulforaphite-germanium type crystal structure, it does not exhibit the same particle size as TiS. x Sufficient contact makes it difficult for lithium ions to be supplied to TiS. xFurthermore, the lithium-ion conductivity does not decrease. In addition, the proportion of Li in glass-ceramic solid electrolytes is relatively small, resulting in low reactivity; therefore, the impact of the decrease in conductivity caused by lithium-ion supply is expected to be minimal. Based on the above, it is believed that compared to crystalline solid electrolytes with a sulforaphite-germanium crystal structure, glass-ceramic solid electrolytes suppress the decrease in lithium-ion conductivity and increase the discharge capacity.

[0195] Example 2

[0196] (1) Fabrication of positive electrode composite material

[0197] Except for changing the mass ratio of positive electrode active material powder A to acetylene black to 87:13 to obtain a composite of positive electrode active material and conductive additive, and changing the mass ratio of sulfide solid electrolyte powder A to the composite of active material and conductive additive to 25:75, the positive electrode composite material was obtained in the same manner as in Example 1.

[0198] (2) Fabrication and evaluation of all-solid-state lithium-ion batteries

[0199] Except for using the positive electrode composite material obtained in (1) above, an all-solid-state lithium-ion battery was fabricated and evaluated in the same manner as in Example 1. Figure 3 The image shows the XRD pattern of the cathode composite material prepared in Example 2.

[0200] Example 3

[0201] (1) Preparation of positive electrode active material powder (titanium sulfide)

[0202] Except for changing the mechanical grinding time to 5 hours, positive electrode active material powder B was obtained in the same manner as in Example 1(1).

[0203] exist Figure 4 The XRD pattern of positive electrode active material B (5-hour MM treatment) is shown. Additionally, XRD patterns of positive electrode active material C (1-hour MM treatment), sulfur (S), and titanium disulfide (TiS2) are shown, as described later.

[0204] (2) Preparation of sulfide solid electrolytes

[0205] 2g of sulfide solid electrolyte powder A obtained in Example 1(2), 7g of cyclohexane, 1g of diisopropyl ether, and 40g of zirconia balls with a diameter of 0.3mm were sealed into a 45mL zirconia container. The container was set in a planetary ball mill (FRITSCH P7 Classic Line) and mechanically ground at 500rpm for 1 hour, followed by mechanical grinding at 150rpm for 1 hour to obtain a slurry. The obtained slurry was vacuum dried at 120°C for 2 hours, and the obtained powder was heat-treated on a hot plate at 180°C for 2 hours to obtain sulfide solid electrolyte powder D.

[0206] The ionic conductivity of sulfide solid electrolyte powder D is 2.9 mS / cm. -1 The average particle size d50 is 2 μm.

[0207] exist Figure 5 The XRD pattern of sulfide solid electrolyte powder D is shown. Peaks originating from the solid electrolyte were observed at 2θ = 20.2°, 23.5°, 37.1°, and 40.7°.

[0208] (3) Fabrication of positive electrode composite materials

[0209] Weigh the positive electrode active material powder B and acetylene black at a mass ratio of 87:13 and mix them for 5 minutes using an agate mortar. Seal the resulting powder together with 100 zirconia balls with a diameter of 5 mm into a 45 mL zirconia jar and mix them using a planetary ball mill (FRITSCH P7 Classic Line) at 370 rpm for 1 hour to obtain a composite of positive electrode active material and conductive additive.

[0210] Next, sulfide solid electrolyte powder D was added to the container at a mass ratio of 25:75 to the composite of positive electrode active material and conductive additive (electrolyte powder D: composite), and then mixed for 30 minutes at 100 rpm using a planetary ball mill to obtain the positive electrode composite material.

[0211] exist Figure 6 The image shows the XRD pattern of the cathode composite material prepared in Example 3.

[0212] (4) Fabrication and evaluation of all-solid-state lithium-ion batteries

[0213] Except for the positive electrode composite material obtained in (3) above, the all-solid-state lithium-ion battery was fabricated and evaluated in the same manner as in Example 1.

[0214] Example 4

[0215] (1) Fabrication of positive electrode composite material

[0216] The positive electrode composite material was obtained in the same manner as in Example 3, except that sulfide solid electrolyte powder A was used instead of sulfide solid electrolyte powder D.

[0217] (2) Fabrication and evaluation of all-solid-state lithium-ion batteries

[0218] Except for using the positive electrode composite material obtained in (1) above, an all-solid-state lithium-ion battery was fabricated and evaluated in the same manner as in Example 1. Figure 7 The image shows the XRD pattern of the cathode composite material prepared in Example 4.

[0219] Example 5

[0220] (1) Preparation of positive electrode active material powder (titanium sulfide)

[0221] Except for changing the mechanical grinding time to 1 hour, the positive electrode active material powder C was obtained in the same manner as in Example 1 (1).

[0222] (2) Fabrication of positive electrode composite materials and all-solid-state lithium-ion batteries

[0223] Except for replacing positive electrode active material powder B with positive electrode active material powder C, the positive electrode composite material and all-solid-state lithium-ion battery were fabricated in the same manner as in Example 3. Figure 8 The XRD patterns of the cathode composite materials prepared in Examples 5-7 are shown in the figure.

[0224] Example 6

[0225] (1) Fabrication of positive electrode composite material

[0226] The positive electrode active material powder C and the sulfide solid electrolyte powder D were weighed at a mass ratio of 75:25 and sealed together with 100 zirconia balls with a diameter of 5 mm in a 45 mL zirconia container. The container was set in a planetary ball mill (FRITSCH P7 Classic Line) and mixed at 100 rpm for 30 minutes to obtain the positive electrode composite material.

[0227] (2) Fabrication of all-solid-state lithium-ion batteries

[0228] In addition to using the positive electrode composite material obtained in (1) above, an all-solid-state lithium-ion battery was fabricated and evaluated in the same manner as in Example 1.

[0229] Example 7

[0230] (1) Fabrication of positive electrode composite material

[0231] Weigh the positive electrode active material powder C and acetylene black at a mass ratio of 90:10 and mix them for 5 minutes using an agate mortar. Seal the resulting powder together with 100 zirconia balls with a diameter of 5 mm into a 45 mL zirconia jar and mix them using a planetary ball mill (FRITSCH P7 Classic Line) at 370 rpm for 1 hour to obtain a composite of positive electrode active material and conductive additive.

[0232] Next, sulfide solid electrolyte powder D was added to the container at a mass ratio of 17:83 to the composite of positive electrode active material and conductive additive (solid electrolyte powder D: composite). The mixture was then further mixed at 100 rpm for 30 minutes using a planetary ball mill to obtain the positive electrode composite material.

[0233] (2) Fabrication of all-solid-state lithium-ion batteries

[0234] In addition to using the positive electrode composite material obtained in (1) above, an all-solid-state lithium-ion battery was fabricated and evaluated in the same manner as in Example 1.

[0235] Example 8

[0236] (1) Preparation of positive electrode active material powder (titanium sulfide)

[0237] In an argon-atmospheric glove box, titanium disulfide (TiS2) powder and sulfur (S) powder were weighed in a molar ratio of 1:4 and sealed together with 90g of zirconia balls with a diameter of 4mm in a 45mL zirconia container. The container was mechanically ground at 510rpm for 1 hour in a planetary ball mill (FRITSCH P7 Classic Line) to obtain positive electrode active material powder D.

[0238] (2) Fabrication of positive electrode composite material

[0239] In addition to using the positive electrode active material powder D obtained in (1) above, the positive electrode composite material was obtained in the same manner as in Example 7.

[0240] (3) Fabrication of all-solid-state lithium-ion batteries

[0241] In addition to using the cathode composite material obtained in (2) above, an all-solid-state lithium-ion battery was fabricated and evaluated in the same manner as in Example 1.

[0242] The batteries prepared in Examples 2-8 were evaluated in the same manner as in Example 1, and the results are shown in Table 2.

[0243] [Table 2]

[0244]

[0245] It was confirmed that if titanium sulfides with a residual TiS2 crystal phase of high electronic conductivity are used, the discharge capacity will be further increased.

[0246] Furthermore, it was confirmed that since titanium sulfide, as the positive electrode active material, has both electronic conductivity and lithium-ion conductivity, the amount of conductive additives and sulfide solid electrolyte mixed in the positive electrode composite material can be reduced.

[0247] Industrial applicability

[0248] The positive electrode composite material of the present invention is suitable as a constituent material of lithium-ion batteries. Furthermore, the lithium-ion battery of the present invention is preferably used, for example, in batteries used in information-related devices or communication devices such as personal computers, cameras, and mobile phones, and in vehicles such as electric vehicles.

[0249] In the foregoing, several embodiments and / or examples of the present invention have been described in detail. However, those skilled in the art can readily make various modifications to these embodiments and / or examples without substantially departing from the new insights and effects of the present invention. Therefore, these various modifications are included within the scope of the present invention.

[0250] All references to the literature recorded in this specification and the contents of the application which form the basis of the priority claim under the Paris Convention are incorporated herein by reference.

Claims

1. A positive electrode composite material, characterized in that, Comprising: titanium sulfide TiS x and at least one of the discharge products of the titanium sulfide, where 2 < x < 10; and The sulfide solid electrolyte has a diffraction peak at 2θ = 20.1 ± 0.4° in X-ray diffraction using CuKα radiation.

2. The positive electrode composite material as described in claim 1, characterized in that, The sulfide solid electrolyte contains lithium, phosphorus, sulfur, and a halogen as constituent elements.

3. The positive electrode composite material as described in claim 1 or 2, characterized in that, The content of lithium relative to all the constituent elements of the sulfide solid electrolyte is 35 to 45 mol%.

4. The positive electrode composite material according to any one of claims 1 to 3, characterized in that, The content a of the titanium sulfide, the content b of the sulfide solid electrolyte, and the content c of the conductive aid satisfy the following formulas (1) to (3). 10 mass% ≤ a ≤ 90 mass% (1) 0 mass% < b ≤ 65 mass% (2) 0 mass% ≤ c ≤ 40 mass% (3) a + b + c is 100 mass%.

5. The positive electrode composite material according to any one of claims 1 to 4, characterized in that, In X-ray diffraction using CuKα radiation, it has a diffraction peak at 2θ = 20.1 ± 0.4°, a diffraction peak at 2θ = 34 ± 1°, and one or more diffraction peaks selected from 2θ = 15.5 ± 1°, 44 ± 1°, and 54 ± 1°.

6. The positive electrode composite material as described in claim 4, characterized in that, The content c of the conductive aid is 0 mass%.

7. A method for manufacturing a positive electrode composite material, characterized in that, Including titanium sulfide TiS that satisfies (A) below x The process of mixing with a sulfide solid electrolyte that satisfies (B) below, wherein, 2 <x<10, (A) In X-ray diffraction using CuKα radiation, it has a diffraction peak at 2θ = 34 ± 1° and one or more diffraction peaks selected from 2θ = 15.5 ± 1°, 44 ± 1°, and 54 ± 1°. (B) In X-ray diffraction using CuKα radiation, it has a diffraction peak at 2θ = 20.1 ± 0.4°.

8. The method for manufacturing the positive electrode composite material as described in claim 7, characterized in that, The average particle size of the sulfide solid electrolyte is 10 μm or less.

9. The method for manufacturing the positive electrode composite material as described in claim 7 or 8, characterized in that, It includes a step of synthesizing the titanium sulfide by mechanically mixing sulfur and titanium disulfide.

10. A positive electrode composite material, characterized in that, Obtained by the manufacturing method of the positive electrode composite material according to any one of claims 7 to 9.

11. A positive electrode, characterized in that, It contains the positive electrode composite material according to any one of claims 1 to 6 and 10.

12. A lithium-ion battery, characterized in that, It contains the positive electrode according to claim 11.

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