Positive electrode mixture, method for manufacturing positive electrode mixture, and lithium-ion battery

Abstract

In the present invention, a positive electrode mixture includes an electrically conductive assistant, a sulfur-based active material, and a solid electrolyte, wherein the positive electrode mixture has a 50% or higher rate of overlap in mapping of carbon and phosphorus in an elemental analysis by energy dispersive X-ray spectroscopy of an electron microscope image, and has a diffraction peak A at 2θ=20.2±0.5° and a diffraction peak B at 2θ=41.1±0.8° in a powder X-ray diffraction using CuKα rays.

Description

Positive electrode mixture, method for producing the positive electrode mixture, and lithium ion battery

[0001] The present invention relates to a positive electrode composite, a method for manufacturing the positive electrode composite, and a lithium ion battery. Specifically, the present invention relates to a positive electrode composite that can exhibit excellent rate characteristics, a method for manufacturing the positive electrode composite, and a lithium ion battery.

[0002] In sulfur-based positive electrode composites used in lithium-ion batteries and the like, the reaction of insulating sulfur can be sufficiently induced by compounding sulfur with a conductive additive and a solid electrolyte (SE) (Patent Document 1).

[0003] JP 2013-258079 A

[0004] However, in terms of further improving rate characteristics, it has been found that there is room for further improvement in conventional techniques including that of Patent Document 1.

[0005] An object of the present invention is to provide a positive electrode mixture that can exhibit excellent rate characteristics, a method for producing the positive electrode mixture, and a lithium ion battery.

[0006] As a result of extensive research, the inventors discovered that a cathode mixture satisfying certain conditions can exhibit excellent rate characteristics, leading to the completion of the present invention. According to the present invention, the following cathode mixtures and the like can be provided. 1. A cathode mixture comprising a conductive additive that is a carbon material, a sulfur-based active material, and a solid electrolyte, wherein, in elemental analysis of electron microscope images by energy dispersive X-ray spectroscopy, the overlap rate of carbon and phosphorus mapping is 50% or more, and in powder X-ray diffraction using CuKα radiation, the cathode mixture has a diffraction peak A at 2θ = 20.2 ± 0.5° and a diffraction peak B at 2θ = 41.1 ± 0.8°. 2. The cathode mixture according to 1, wherein the half-width of the diffraction peak B is 1.15° or less. 3. The cathode mixture according to 1 or 2, wherein the solid electrolyte contains lithium atoms, phosphorus atoms, sulfur atoms, bromine atoms, and iodine atoms. 4. The cathode mixture according to any one of 1 to 3, wherein the weight loss rate when heat-treated at 190°C for 2 hours is 2.5% or more. 5. The cathode mixture according to any one of 1 to 4, wherein the weight loss rate of the sulfur-based active material when heat-treated at 190°C for 2 hours is 7.0% or more. 6. The cathode mixture according to any one of 1 to 5, obtained by a production method including a first mixing step of adding a solid electrolyte to a sulfur-based active material and mixing the mixture to obtain a first mixture, and a second mixing step of adding a further solid electrolyte to the first mixture and mixing the mixture to obtain a second mixture, wherein the second mixing step uses less energy than the first mixing step. 7. The cathode mixture according to 6, wherein the first mixing step is performed under conditions that cause the solid electrolyte added in the first mixing step to become amorphous, and the second mixing step is performed under conditions that do not cause the crystallinity of the solid electrolyte added in the second mixing step to be lost. 8. A method for producing a positive electrode composite, comprising: a first mixing step of adding a solid electrolyte to a sulfur-based active material and performing a mixing process to obtain a first mixture; and a second mixing step of adding a further solid electrolyte to the first mixture and performing a mixing process to obtain a second mixture, wherein the mixing process in the second mixing step is performed with less energy than in the first mixing step.9. The method for producing a cathode composite according to 8, wherein the first mixing step is performed under conditions that cause the solid electrolyte added in the first mixing step to become amorphous, and the second mixing step is performed under conditions that do not cause the crystallinity of the solid electrolyte added in the second mixing step to be lost. 10. The method for producing a cathode composite according to 8 or 9, which produces the cathode composite according to any one of 1 to 7. 11. A lithium ion battery comprising the cathode composite according to any one of 1 to 7.

[0007] According to the present invention, it is possible to provide a positive electrode composite that can exhibit excellent rate characteristics, a method for manufacturing the positive electrode composite, and a lithium ion battery.

[0008] 1 shows the results of energy dispersive X-ray spectroscopy (SEM-EDS analysis) of electron microscope images of Example 1 (in FIG. 1 and the following FIGS. 2 to 9, (a) shows the image before image processing, and (b) shows the image after image processing. Also, C shows carbon mapping, and P shows phosphorus mapping). FIG. 1 shows the results of SEM-EDS analysis of Example 2. FIG. 2 shows the results of SEM-EDS analysis of Comparative Example 1. FIG. 3 shows the results of SEM-EDS analysis of Comparative Example 2. FIG. 4 shows the results of SEM-EDS analysis of Example 3. FIG. 5 shows the results of SEM-EDS analysis of Example 4. FIG. 6 shows the results of SEM-EDS analysis of Example 5. FIG. 7 shows the results of SEM-EDS analysis of Example 6. FIG. 8 shows the results of SEM-EDS analysis of Example 7. FIG. 9 shows the results of powder X-ray diffraction (XRD) of Examples 1 and 2, Comparative Examples 1 and 2, and Reference Example 1. FIG. 10 shows the results of XRD of Examples 3 and 4. FIG. 11 shows the results of XRD of Examples 5, 6, and Comparative Example 3. FIG. 1 is a diagram showing the results of XRD for Example 7 and Comparative Example 4.

[0009] The cathode composite, the manufacturing method for the cathode composite, and the lithium-ion battery of the present invention will be described in detail below. In this specification, "x to y" represents a numerical range of "x or more and y or less." The upper and lower limits of the numerical ranges can be combined in any combination.

[0010] 1. Cathode Composite A cathode composite according to one embodiment of the present invention includes a conductive additive that is a carbon material, a sulfur-based active material, and a solid electrolyte, and in elemental analysis of electron microscope images by energy dispersive X-ray spectroscopy, the carbon and phosphorus mapping overlap rate is 50% or more, and in powder X-ray diffraction using CuKα radiation, the cathode composite has a diffraction peak A at 2θ = 20.2 ± 0.5° and a diffraction peak B at 2θ = 41.1 ± 0.8°. The cathode composite according to this embodiment exhibits excellent rate characteristics.

[0011] The overlap rates are values ​​measured based on smoothed, compressed, and binarized carbon and phosphorus mappings, specifically, values ​​measured by the method described in the Examples. The powder X-ray diffraction is also measured by the method described in the Examples.

[0012] In the positive electrode composite according to this embodiment, the sulfur-based active material and the solid electrolyte are well mixed, as specified by the overlapping ratio. Furthermore, as specified by the diffraction peaks, the crystallinity of the solid electrolyte is well maintained, and therefore, Li ＋ As a result, excellent rate characteristics are demonstrated.

[0013] A cathode composite such as this embodiment could not be produced by conventional techniques. That is, when a method of adding a solid electrolyte to a sulfur-carbon composite and mechanically mixing it by applying strong energy was used, the crystallinity of the solid electrolyte was reduced by the mechanical mixing, and Li ＋ Furthermore, when a cathode composite is prepared by mechanically mixing with low energy, as in the technique of Patent Document 1, the deterioration of the crystallinity of the solid electrolyte is suppressed, but the sulfur-carbon composite and the solid electrolyte cannot be well mixed, making it more difficult to improve the rate characteristics.

[0014] In one embodiment, the overlap rate is preferably 50% or more, more preferably 55% or more, and particularly preferably 57% or more. The upper limit is not particularly limited and may be 100%, but may also be, for example, 90% or less or 80% or less.

[0015] In this aspect, the positive electrode composite has a diffraction peak A at 2θ = 20.2 ± 0.5° and a diffraction peak B at 2θ = 41.1 ± 0.8° in powder X-ray diffraction using CuKα radiation. Diffraction peaks A and B are derived from crystals contained in the solid electrolyte. In one embodiment, the positive electrode composite may further have a diffraction peak at 2θ = 23.6 ± 0.5°.

[0016] In one embodiment, the half width of the diffraction peak B is 1.15° or less. This allows the Li of the solid electrolyte in the positive electrode mixture to be ＋ The conductivity is further improved, and the rate characteristics are further improved. The half-width of diffraction peak B is a value obtained by subtracting the apparatus constant, and is specifically calculated by the method described in the Examples. By using a solid electrolyte with good crystallinity (a solid electrolyte with a narrow half-width of diffraction peak B) as a raw material and mixing it so as to minimize the decrease in crystallinity during the production of the positive electrode composite, the half-width of diffraction peak B can be made 1.15° or less. If the crystallinity of the solid electrolyte is excessively destroyed during mixing, even if recrystallization is attempted by subsequent heating, the half-width of diffraction peak B cannot be made 1.15° or less.

[0017] 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. The sulfur is not particularly limited, but 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.

[0018] The solid electrolyte contains a thiolicon region II type crystal structure. This allows the above-mentioned diffraction peaks A and B to be observed. Here, the "thiolicon region II type crystal structure" refers to a structure in which Li ４－ xGe 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－ xGe １－ｘ P ｘ S ４ This indicates that the thio-LISICON region II type has a similar crystal structure (see Solid State Ionics, 177 (2006), 2721-2725).

[0019] The solid electrolyte may have the thiolicon region II crystal structure or may have it as the main crystal. From the viewpoint of obtaining higher ionic conductivity, it is preferable that it has it as the main crystal. In this specification, "having it as the main crystal" means that the proportion of the target crystal structure in the crystal structure is 80% or more, preferably 90% or more, and more preferably 95% or more.

[0020] In one embodiment, the solid electrolyte contains lithium atoms, phosphorus atoms, sulfur atoms, bromine atoms, and iodine atoms, which further improves ionic conductivity and rate capability. In this embodiment, the compounding ratio (molar ratio) of lithium atoms, sulfur atoms, phosphorus atoms, bromine atoms, and iodine atoms is not particularly limited, but 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.

[0021] The conductive additive, which is a carbon material, may be any material that is electronically conductive. The conductive additive preferably has a plurality of pores. A carbon material having pores is particularly preferred. Carbon materials have high conductivity and are lighter than other conductive materials, so the output density and capacity per unit weight of the battery can be increased. The specific surface area of ​​the conductive additive is 0.1 m ２ / g or more 5000m ２ / g or less, and more preferably 1m ２ / g or more 4000m ２ / g or less, and more preferably 1m ２ / g or more 3000m ２ / g or less, and most preferably 10m ２ / g or more 3000m ２ The pore volume of the conductive additive is preferably 0.1 cc / g or more and 5.0 cc / g or less. The pores of the conductive additive preferably have an average diameter of 0.1 nm or more and 40 nm or less, more preferably 0.5 nm or more and 40 nm or less, even more preferably 0.5 nm or more and 20 nm or less, and most preferably 1 nm or more and 20 nm or less.

[0022] The specific surface area, pore volume, and pore diameter of the conductive additive can be determined using a nitrogen adsorption isotherm obtained by adsorbing nitrogen gas to the conductive additive at liquid nitrogen temperature. Specifically, the specific surface area can be calculated using the nitrogen adsorption isotherm by the Brenauer-Emmet-Telle (BET) multipoint method. Furthermore, the pore volume and pore diameter can be determined using the nitrogen adsorption isotherm by the Barret-Joyner-Halenda (BJH) method. As a measuring device, for example, a specific surface area and pore distribution measuring device (Autosorb-3) manufactured by Quantacrome can be used for measurement.

[0023] The carbon material is not particularly limited, but examples thereof include carbon black such as ketjen black, acetylene black, denka black, thermal black, and channel black, mesoporous carbon, activated carbon, amorphous carbon, carbon nanotubes, vapor-grown carbon fiber (VGCF), and carbon nanohorns. Examples of conductive carbon materials include fullerene, carbon fiber, natural graphite, artificial graphite, graphene, graphene oxide, and reduced graphene oxide. These may be used alone or in combination of two or more. Composites of these may also be used.

[0024] Mesoporous carbon is a carbon material having two-dimensional or three-dimensional pores, which can be obtained by the production method described in the following documents: S. J. Sang, S. H. Joo, R. Ryoo, et., J. Am. Chem. Soc., 122 (2000) 10712-10713, and T. Yokoi, Y. Sakamoto, O. Terasaki, et., J. Am. Chem. Soc., 128 (2006) 13664-13665.

[0025] In one embodiment, the positive electrode composite may or may not contain components other than the sulfur-based active material, the solid electrolyte, and the conductive additive. The other components are not particularly limited, and examples thereof include a binder, a solvent, a dispersant, and the like.

[0026] In the positive electrode mixture, the contents of the sulfur-based active material, solid electrolyte, and conductive additive are not particularly limited. In one embodiment, the content of the sulfur-based active material is 40 to 350 parts by mass per 100 parts by mass of the solid electrolyte. In one embodiment, the content of the conductive additive is 10 to 300 parts by mass per 100 parts by mass of the solid electrolyte. In one embodiment, 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, 99% by mass or more, 99.5% by mass or more, or substantially 100% by mass of the positive electrode mixture is the conductive additive, sulfur-based active material, and solid electrolyte. Note that "substantially 100% by mass" may include inevitable impurities.

[0027] In one embodiment, the positive electrode composite exhibits a weight loss rate of 2.5% or more, preferably 3.0% or more, and more preferably 3.5% or more, when heat-treated at 190°C for 2 hours. In one embodiment, the positive electrode composite exhibits a weight loss rate of 7.0% or more, preferably 9.0% or more, and more preferably 11.0% or more, when heat-treated at 190°C for 2 hours. The weight loss rate (particularly the sulfur-based active material weight loss rate) when heat-treated at 190°C for 2 hours can occur because the conductive additive, which is a carbon material, is sufficiently pulverized, making it easier for the sulfur filled in the carbon pores to be released by heating. Therefore, the higher the weight loss rate (particularly the sulfur-based active material weight loss rate), the higher the dispersibility of each component in the positive electrode composite. As a result, the positive electrode composite can exhibit better rate characteristics. The weight loss rate and sulfur-based active material weight loss rate described above are values ​​measured by the method described in the examples.

[0028] 2. Manufacturing Method of Cathode Composite A manufacturing method of a cathode composite according to one aspect of the present invention includes a first mixing step in which a solid electrolyte is added to a sulfur-based active material and mixed to obtain a first mixture, and a second mixing step in which a further solid electrolyte is added to the first mixture and mixed to obtain a second mixture, the second mixing step being performed with less energy than the first mixing step. According to this manufacturing method of a cathode composite, a cathode composite capable of exhibiting excellent rate characteristics can be obtained. That is, the sulfur-based active material and the solid electrolyte can be sufficiently mixed in the first mixing step, and the second mixing step is performed with less energy than the first mixing step, thereby favorably maintaining the crystallinity of the solid electrolyte. As a result, a good mixing state and crystallinity are both achieved, resulting in improved rate characteristics.

[0029] In this embodiment, the conductive additive and the sulfur-based active material can be described in the same manner as in the positive electrode composite material. The solid electrolyte added in the first mixing step and the solid electrolyte added in the second mixing step may be the same or different. The solid electrolyte added in the first mixing step may be a single type, or two or more types may be used in combination. The solid electrolyte added in the second mixing step may be a single type, or two or more types may be used in combination.

[0030] The solid electrolyte used in the first mixing step 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 the contained metal atoms. In addition to sulfur atoms, it preferably contains lithium atoms and phosphorus atoms, more preferably lithium atoms, phosphorus atoms, and halogen atoms, and has ionic conductivity due to lithium atoms. In one embodiment, the solid electrolyte contains lithium atoms, phosphorus atoms, sulfur atoms, bromine atoms, and iodine atoms. The sulfide solid electrolyte may be an amorphous sulfide solid electrolyte or a crystalline sulfide solid electrolyte.

[0031] (Amorphous sulfide solid electrolyte) The amorphous sulfide solid electrolyte can be used without any particular limitation as long as it contains at least sulfur atoms and exhibits ionic conductivity due to the contained metal atoms. Representative examples include Li ２ S-P ２ S ５ a solid electrolyte containing sulfur atoms, lithium atoms, and phosphorus atoms, which is composed of lithium sulfide and phosphorus sulfide such as Li; ２ S-P ２ S ５ - LiI, Li ２ S-P ２ S ５ -LiCl, Li ２ S-P ２ S ５ - LiBr, Li ２ S-P ２ S ５ -LiI-LiBr, etc., 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.

[0032] The amorphous sulfide solid electrolyte contains at least Li ２S-P ２ S ５ When Li ２ S and P ２ S ５ From the viewpoint of obtaining high chemical stability and higher ionic conductivity, the molar ratio of Li to Li is preferably 30 to 85:15 to 70, more preferably 40 to 80:20 to 60, and even more preferably 45 to 78:22 to 55. ２ S-P ２ S ５ In the case of -LiI-LiBr, the total content of lithium sulfide and diphosphorus pentasulfide is preferably 30 to 95 mol%, more preferably 35 to 90 mol%, and even more preferably 40 to 85 mol%. The ratio of lithium bromide to the total of lithium bromide and lithium iodide is preferably 1 to 99 mol%, more preferably 20 to 90 mol%, even more preferably 40 to 80 mol%, and particularly preferably 50 to 70 mol%.

[0033] 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.

[0034] (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 ７P.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).

[0035] The crystalline sulfide solid electrolyte containing lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms may have the following crystalline structure: ４－ｘ Ge １－ｘ P ｘ S ４ Thio-LISICON Region II crystal structure, Li ４－ｘ Ge １－ｘ P ｘ S ４ Examples include a crystal structure similar to that of thio-LISICON Region II type.

[0036] 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 Ge１－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°.

[0037] The crystal structure of the crystalline sulfide solid electrolyte also includes an argyrodite-type crystal structure. ７ P.S. ６ Crystal structure; Li ７ P.S. ６ The structural skeleton of the composition formula Li ７－ｘ P １－ｙ Si ｙ S ６ and Li ７＋ｘ P １－ｙ Si ｙ S ６ (x is -0.6 to 0.6, y is 0.1 to 0.6); Li ７－ｘ－２ｙ P.S. ６－ｘ－ｙ Cl ｘ (0.8≦x≦1.7, 0<y≦−0.25x+0.5); Li ７－ｘ P.S. ６－ｘ Ha ｘ (Ha is Cl or Br, and x is preferably 0.2 to 1.8).

[0038] 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.

[0039] 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.

[0040] The amount of the solid electrolyte used in the first mixing step is preferably 1 to 80%, and more preferably 5 to 75%, of the total mass of the solid electrolytes added in the first and second mixing steps.

[0041] As described above, the solid electrolyte used in the second mixing step contains a thiolicon region II crystal structure. The amount of solid electrolyte used in the second mixing step is preferably 20 to 99%, more preferably 25 to 95%, of the total mass of the solid electrolyte added in the first and second mixing steps. The ratio of the total mass of the solid electrolyte added in the first and second mixing steps to the total mass of the sulfur-based active material and conductive additive (solid electrolyte:sulfur-based active material + conductive additive) is 10:90 to 90:10, preferably 15 to 70:85 to 30, and more preferably 20 to 60:80 to 40.

[0042] In one embodiment, when a crystalline solid electrolyte is used in the first mixing step, the first mixing step is performed under conditions that promote amorphization of the solid electrolyte added in the first mixing step, and the second mixing step is performed under conditions that maintain the crystallinity of the solid electrolyte added in the second mixing step. This can further improve the rate characteristics. The progress of amorphization can be determined by the broadening of peaks derived from crystalline components in X-ray diffraction measurement.

[0043] The energy of the mixing treatment in each of the first and second mixing steps is not particularly limited as long as the condition of the first mixing step > the second mixing step is satisfied. For example, in the first mixing step, mixing can be performed under conditions that may cause a decrease in the intensity of the crystal peak of the solid electrolyte added in the first mixing step, an increase in the half-width of the peak, or even disappearance of the peak. On the other hand, in the second mixing step, mixing can be performed under conditions that do not cause the crystal peak of the solid electrolyte added in the second mixing step to disappear, preferably under conditions that cause only a small change in the crystal peak intensity or half-width of the peak. Here, "small change" may mean, for example, that the rate of change is smaller than the rate of change in the first mixing step.

[0044] Examples of mixing devices used in the first mixing step include planetary ball mills, tumbling mills, bead mills, Filmix mixers, Nauta mixers, tornado mixers, twin-screw extruders, multi-screw rollers, and solid-phase shear mixers. The mixing devices used in the second mixing step include those exemplified for the first mixing step. However, when selecting a mixing device and setting operating conditions, the mixing energy must satisfy the condition of first mixing step > second mixing step. The devices used in the first and second mixing steps may be the same or different. When using the same device, for example, the processing time or integrated power can be set to be greater than the second mixing step, or, for devices that utilize rotational power, such as planetary ball mills and tumbling mills, the rotation speed can be set to be greater than the first mixing step > second mixing step. In one embodiment, a planetary ball mill is used in the first mixing step. In one embodiment, a tumbling mill is used in the second mixing step.

[0045] In one embodiment, the sulfur-based active material subjected to the first mixing step is pre-composited with the conductive additive. For example, the sulfur-based active material can be composited with the conductive additive by heating the sulfur-based active material together with the conductive additive before the first mixing step. The heating temperature is not particularly limited, and may be, for example, a temperature exceeding 120°C, such as 150°C or higher, 170°C or higher, 200°C or higher, 150°C or higher, 200°C or higher, 250°C or higher, or 300°C or higher. The upper limit is, for example, 350°C or lower. The mass ratio of the sulfur-based active material to the conductive additive (sulfur-based active material:conductive additive) is 10:90 to 95:5, preferably 20 to 80:90 to 10.

[0046] In one embodiment, the positive electrode composite produced by the method for producing a positive electrode composite according to this aspect is the positive electrode composite according to the aspect of the present invention described above.

[0047] 3. Lithium-ion battery A lithium-ion battery according to an aspect of the present invention includes the positive electrode composite according to the aspect of the present invention described above. The lithium-ion battery according to this aspect can exhibit excellent rate characteristics.

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

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

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

[0051] The electrolyte layer is not particularly limited, and known electrolytes can be used. For example, oxide-based solid electrolytes, sulfide-based solid electrolytes, and polymer-based electrolytes are preferred, and sulfide-based solid electrolytes are more preferred from the viewpoint of ionic conductivity. The sulfide-based solid electrolyte is preferably the one used in the above-mentioned positive electrode composite.

[0052] The method for producing a lithium ion battery is not particularly limited, and examples thereof include a method in which a sheet is formed by forming a positive electrode layer made of the positive electrode composite according to one embodiment of the present invention on a positive electrode current collector, forming a solid electrolyte layer on the sheet, and laminating the sheet on which the negative electrode layer is formed on a previously formed negative electrode current collector, followed by pressing.

[0053] Examples of the present invention will be described below, but the present invention is not limited to these examples.

[0054] (Example 1) 1. Preparation of Positive Electrode Composite Material (1) Preparation of Composite Powder A Activated carbon (MSC-30 manufactured by Kansai Thermal Chemical Industries, 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 composite powder A of activated carbon and sulfur.

[0055] (2) Preparation of Solid Electrolyte A 0.4127 g of lithium sulfide, 0.6655 g of diphosphorus pentasulfide, 0.2137 g of lithium iodide, 0.2080 g of lithium bromide, and 10 zirconia balls with a diameter of 10 mm were placed in a 45 mL zirconia pot and sealed. Using a planetary ball mill (manufactured by Fritsch, model number P-7), the mixture was mixed (mechanical milling) for 40 hours at a rotation speed of 370 rpm to obtain a powder. The obtained powder was heated at 195 ° C. for 3 hours to obtain a solid electrolyte A.

[0056] (3) Preparation of Positive Electrode Composite Powder First Mixing Step 0.9 g of composite powder A and 0.18 g of solid electrolyte A were placed in a 45 mL zirconia pot along with 10 10 mm diameter zirconia balls and sealed. Using a planetary ball mill (manufactured by Fritsch, model number P-7), mixing was performed at a rotation speed of 370 rpm for 20 hours at room temperature to obtain composite powder B. Second Mixing Step 0.54 g of composite powder B and 0.36 g of solid electrolyte A were placed in a 45 mL zirconia pot along with 34 g of 2 mm diameter zirconia balls and sealed. Using a tumbling mill ("Small Ball Mill Stand", manufactured by Asahi Rika Seisakusho, model number AV-1), mixing was performed at a rotation speed of 600 rpm for 1 hour at room temperature to obtain a positive electrode composite powder.

[0057] 2. Measurement and Test Methods (1) Energy Dispersive X-ray Spectroscopy (SEM-EDS Analysis) of Electron Microscope Images and Calculation of Carbon and Phosphorus Overlap Rate Preparation of Positive Electrode Composite Pellets 100 mg of solid electrolyte A was placed in a Macol cylinder with a diameter of 10 mm and pressure molded. 20 mg of the obtained positive electrode composite powder was placed on the pressure surface and pressure molded again. Subsequently, 20 mg of the positive electrode composite powder was placed on the opposite pressure surface and pressure molded again, and the molded body was extracted from the cylinder to obtain a positive electrode composite pellet.

[0058] SEM-EDS analysis The positive electrode composite pellet was split vertically, and the exposed surface was subjected to ion milling (Hitachi High-Tech Corporation, IM4000) to expose the cross section of the positive electrode composite pellet. SEM-EDS elemental mapping measurement was performed on the obtained cross section using an SEM (Hitachi High-Tech Corporation, SU8220) and an EDS (Bruker, QUANTAX FlatQUAD), and secondary electron images and EDS images of carbon and phosphorus were obtained from 10 fields of view. The observation magnification was 5000x, the acceleration voltage was 10 kV, and the scan area was 1024 x 768. No special image processing was performed for EDS mapping, and an image on which the actual measured intensity was mapped was used. In addition, during the SEM-EDS elemental mapping measurement, the area cross-sectionally processed by ion milling was divided into two equal parts, top and bottom, and each of the two equal parts was divided into five equal parts on the left and right. The central portion of each of the 10 divided regions was subjected to SEM-EDS elemental mapping at a magnification of 5000 times.

[0059] Calculation of Carbon and Phosphorus Overlap Rates Images obtained using the above procedure were processed using OpenCV (4.5.1) in Python (3.9.9). All 10 fields of view of carbon and phosphorus EDS images were subjected to smoothing twice using a bilateral filter with d = 15, sigmaColor = 64, and sigmaSpace = 64. The resulting images were compressed to one-third of their original pixel size using MaxPooling2D (pool_size = 3, strides = 3) in the neural network open library Keras (2.4.3), and smoothed using a median filter. The smoothed images were grayscaled and binarized with a minimum brightness of 30 for carbon and a maximum brightness of 255 for phosphorus, and a minimum brightness of 40 for phosphorus and a maximum brightness of 255 for carbon. The results of the SEM-EDS analysis, including the above image processing, are shown in Figure 1. The results of Example 2, which will be described later, are shown in FIG. 2 , Comparative Example 1 in FIG. 3 , Comparative Example 2 in FIG. 4 , Example 3 in FIG. 5 , Example 4 in FIG. 6 , Example 5 in FIG. 7 , Example 6 in FIG. 8 , and Example 7 in FIG. 9 . In FIGS. 1 to 9 , (a) shows the image before processing (before smoothing, compression, and binarization), and (b) shows the image after processing. C indicates carbon mapping, and P indicates phosphorus mapping. These processes converted the image data into a numerical matrix of 0 if the element was not present and 255 if the element was present. The overlap rate for one field of view was calculated by dividing the total number of pixels where 255 overlapped at the same coordinate in the carbon and phosphorus numerical matrices by the total number of pixels. The average of the overlap rates for all 10 fields of view was used as the overlap rate for this embodiment.

[0060] (2) Powder X-ray diffraction (XRD) of the positive electrode composite powder XRD measurement was performed on the obtained positive electrode composite powder. Specifically, the positive electrode composite 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 from BRUKER Co., Ltd. under the following measurement conditions. [Measurement conditions] Tube voltage: 30 kV Tube current: 10 mA X-ray wavelength: Cu-Kα ray (1.5418 Å) Optical system: focusing method Slit configuration: Soller slit 4° (on both the 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

[0061] XRD measurements were also performed on a reference sample (Reference Example 1) obtained by weighing 0.45 g of composite powder A and 0.45 g of solid electrolyte A into an agate mortar and mortar-mixing them for 10 minutes. The results are shown in FIG. 10 . The results of Examples 3 and 4, which will be described later, are shown in FIG. 11 , the results of Examples 5, 6, and Comparative Example 3 in FIG. 12 , and the results of Example 7 and Comparative Example 4 in FIG. 13 . Based on these results, the presence or absence of diffraction peak A at 2θ = 20.2 ± 0.5° and diffraction peak B at 2θ = 41.1 ± 0.8° was confirmed. The half-width of diffraction peak B was also determined using the following method.

[0062] Calculation of the half-width of diffraction peak B The peak half-width (β) of the positive electrode composite was calculated by subtracting the instrument constant (B) specific to the measurement device from the half-width (w) obtained by measurement, as follows: β = w - B. w: Half-width of the peak (diffraction peak B) at 41.1° ± 0.8° obtained by measurement. B: Instrument constant (a standard material (silicon) was measured in the same way, and B = 0.1269° was obtained from the peak at 2θ = 28.4°.) w (half-width obtained by measurement) was calculated as follows. A linear baseline was set for the peak shape obtained by XRD measurement, and the difference between the intensity and the baseline at each point was calculated to obtain an XRD curve. The XRD curve was fitted with the equation (f(x) = (1 - α) × L(x) + α × G(x)) consisting of a Lorentzian function L(x) and a Gaussian function G(x), and the parameters A (corrected peak intensity), w, and x were calculated by curve fitting. ０ (2θ of the peak top) and α (the ratio of the Lorentzian function) were determined.

[0063]

[0064] In curve fitting, a range of approximately ±1.0° from the peak top is appropriately set as the fitting range. Fitting was performed by taking the error between the intensity of the fitting curve calculated by f(x) at each θ and the intensity of the XRD curve, and minimizing the sum of the errors over the entire fitting range. Here, the solver function (GRG nonlinear) of spreadsheet software (Excel, Microsoft) was used.

[0065] (3) Heating Weight Loss Measurement Test The following measurements were performed on the obtained positive electrode composite powder. First, an aluminum foil petri dish (Tokyo Glass Instruments, volume 12 mL) was weighed. Each positive electrode composite powder was weighed out to 0.2000 g (with an error of ±0.0005 g or less) into the weighed petri dish, and the powder was leveled to distribute as uniformly as possible on the bottom of the petri dish. The aluminum foil petri dish was placed on a hot plate (ND-1A, AS ONE), and covered with two types of stainless steel petri dishes (φ50 mm × height 15 mm, φ60 mm × height 20 mm). The temperature was increased to 190 °C and then kept constant for 2 hours for heat treatment. After the heat treatment, the aluminum foil petri dish with the powder placed thereon was gradually cooled and then weighed. The weight loss (ΔW) of the powder during the heat treatment was calculated by subtracting the total weight of the powder and the aluminum foil petri dish at this time from the total weight measured before heating. The weight loss rate was calculated by dividing the ΔW by the weight of the powder before the heat treatment and converting the result into a percentage. The weight loss rate of the sulfur-based active material was also calculated by dividing the ΔW by the weight of the sulfur-based active material before the heat treatment, which is obtained by multiplying the weight of the powder before the heat treatment by the weight fraction of the sulfur-based active material, and converting the result into a percentage.

[0066] (4) Evaluation of Battery Characteristics Preparation of Lithium-Ion Battery (All-Solid State) 100 mg of solid electrolyte A prepared by the above procedure was pressure-molded in a Macol cylinder with a diameter of 10 mm. The cathode composite powder prepared above was placed on the pressure surface so that the sulfur content was 1.75 mg, and pressure-molded again. Indium foil and lithium foil were placed on the pressure surface opposite the cathode composite, and pressure was applied to prepare an all-solid-state battery. A constant current charge / discharge test was performed on the obtained all-solid-state battery. The voltage range for the constant current charge / discharge test was set to 0.8-2.2 V, and the current value was set under the conditions in Table 1 below. The discharge capacity at 1 C (per sulfur mass) was measured at the 7th cycle under the following conditions.

[0067]

[0068] Example 2 First Mixing Step: 0.9 g of composite powder A obtained in the same manner as in Example 1 and 0.09 g of solid electrolyte A obtained in the same manner as in Example 1 were placed in a 45 mL zirconia pot along with ten 10 mm diameter zirconia balls and sealed. Using a planetary ball mill (manufactured by Fritsch, model number P-7), mixing was carried out at a rotation speed of 370 rpm for 20 hours at room temperature to obtain composite powder C. Second Mixing Step: 0.495 g of composite powder C and 0.405 g of solid electrolyte A were placed in a 45 mL zirconia pot along with 34 g of 2 mm diameter zirconia balls and sealed. Using a tumbling mill ("Small Ball Mill Stand," manufactured by Asahi Rika Seisakusho, model number AV-1), mixing was carried out at a rotation speed of 600 rpm for 1 hour at room temperature to obtain a positive electrode composite powder. The obtained positive electrode composite powder was subjected to the same measurements and tests as in Example 1.

[0069] Comparative Example 1 0.45 g of composite powder A obtained in the same manner as in Example 1 and 0.45 g of solid electrolyte A obtained in the same manner as in Example 1 were placed in a 45 mL zirconia pot together with ten zirconia balls having a diameter of 10 mm and sealed. Using a planetary ball mill (manufactured by Fritsch, model number P-7), mixing was carried out at a rotation speed of 370 rpm for 20 hours at room temperature to obtain a positive electrode composite powder. The obtained positive electrode composite powder was subjected to the same measurements and tests as in Example 1.

[0070] Comparative Example 2 0.45 g of composite powder A obtained in the same manner as in Example 1 and 0.45 g of solid electrolyte A obtained in the same manner as in Example 1 were placed in a 45 mL zirconia pot together with 34 g of zirconia balls having 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 a rotation speed of 600 rpm for 20 hours at room temperature to obtain a positive electrode composite powder. The obtained positive electrode composite powder was subjected to the same measurements and tests as in Example 1.

[0071] (Example 3) First mixing step: Composite powder B was obtained using the same procedure as in Example 1. Second mixing step: 0.54 g of composite powder B and 0.36 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 number AV-1), mixing was carried out at a rotation speed of 600 rpm for 20 hours at room temperature, thereby obtaining a positive electrode composite powder. The obtained positive electrode composite powder was subjected to the same measurements and tests as in Example 1.

[0072] (Example 4) (1) Preparation of solid electrolyte B 0.2058 g of lithium sulfide, 0.9942 g of diphosphorus pentasulfide, and ten 10 mm diameter zirconia balls 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 20 hours to obtain a powder. (2) Preparation of positive electrode composite powder First mixing step 0.9 g of composite powder A and 0.18 g of solid electrolyte B were placed in a 45 mL zirconia pot along with ten 10 mm diameter zirconia balls and sealed. Using a planetary ball mill (manufactured by Fritsch, model number P-7), the mixture was mixed at a rotation speed of 370 rpm for 20 hours at room temperature to obtain a composite powder D. Second Mixing Step: 0.54 g of composite powder D and 0.36 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 number AV-1), mixing was carried out at a rotation speed of 600 rpm for 1 hour at room temperature to obtain a positive electrode composite powder. The obtained positive electrode composite powder was subjected to the same measurements and tests as in Example 1.

[0073] The results are shown in Table 2. Note that the battery characteristics, i.e., the capacity obtained at each charge / discharge rate, are affected by the mass of the active material used (sulfur-based active material in this technology), so it is appropriate to compare under conditions where the active material mass is uniform. Examples 1 to 4 and Comparative Examples 1 and 2 shown in Table 2 have the same active material mass. Similarly, Examples 5 and 6 and Comparative Example 3 shown later in Table 4 also have the same active material mass. Similarly, Example 7 and Comparative Example 4 shown later in Table 6 also have the same active material mass.

[0074]

[0075] (Example 5) 1. Preparation of Cathode Composite (1) Preparation of Solid Electrolyte C 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 vessel to naturally warm to room temperature, stirring was continued 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, which was then 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. ４ 1.70 g of the 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 stirring was continued for 12 hours. The resulting electrolyte precursor content was dried under vacuum at room temperature to obtain a powdered electrolyte precursor. The resulting electrolyte precursor was heated under vacuum at 120°C for 2 hours, and then further heated under vacuum at 140°C for 2 hours to obtain solid electrolyte C.

[0076] (2) Preparation of Positive Electrode Composite Powder First Mixing Step 0.80 g of composite powder A and 0.20 g of solid electrolyte A were placed in a 45 mL zirconia pot along with 10 10 mm diameter zirconia balls and sealed. Using a planetary ball mill (manufactured by Fritsch, model number P-7), mixing was carried out at a rotation speed of 370 rpm for 20 hours at room temperature to obtain composite powder E. Second Mixing Step 0.675 g of composite powder E and 0.225 g of solid electrolyte C were placed in a 45 mL zirconia pot along with 34 g of 2 mm diameter zirconia balls and sealed. Using a tumbling mill ("Small Ball Mill Stand", manufactured by Asahi Rika Seisakusho, model number AV-1), mixing was carried out at a rotation speed of 600 rpm for 1 hour at room temperature to obtain a positive electrode composite powder.

[0077] 2. Measurement and Test Methods (1) Energy Dispersive X-ray Spectroscopy (SEM-EDS Analysis) of Electron Microscope Images and Calculation of the Overlap Rate of Carbon and Phosphorus SEM-EDS analysis was performed in the same manner as in Example 1, and the overlap rate was calculated. (2) Powder X-ray Diffraction (XRD) of Positive Electrode Composite Powder XRD measurement was performed in the same manner as in Example 1, and the half-width of diffraction peak B was calculated. (3) Test for Measuring Weight Loss Rate Upon Heating The same test as in Example 1 was performed.

[0078] (4) Evaluation of battery characteristics Preparation of negative electrode composite LTO (Ishihara Sangyo Kaisha, Ltd. "LT-112"), conductive additive (Denka Co., Ltd. "Li-100", powdered acetylene black), and Li ２ S-P ２ S ５ The solid electrolyte A and LiCl-LiBr type solid electrolyte D were mixed in a mortar at a mass ratio of 60:5:35 for 5 minutes to obtain an LTO negative electrode composite. Preparation of Lithium-ion Battery (All-Solid State) 100 mg of the solid electrolyte A prepared by the above procedure was pressure-molded in a Macol cylinder with a diameter of 10 mm. The cathode composite powder prepared above was added to the pressurized surface so that the sulfur content was 5.04 mg, and the mixture was again pressure-molded. 166 mg of the LTO negative electrode composite was added to the pressurized surface opposite the cathode composite and pressure-molded. A Li foil with a diameter of 9 mm and a thickness of 0.1 mm was added on top and pressure-molded again to produce an all-solid-state battery. A constant current charge / discharge test was performed on the obtained all-solid-state battery. 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 to the conditions in Table 3 below. The discharge capacity at 0.5 C (per mass of sulfur) was measured at the seventh cycle under the following conditions.

[0079]

[0080] Example 6 First Mixing Step: 0.75 g of composite powder A and 0.25 g of solid electrolyte A were placed in a 45 mL zirconia pot along with ten 10 mm diameter zirconia balls and sealed. Using a planetary ball mill (manufactured by Fritsch, model number P-7), mixing was carried out at a rotation speed of 370 rpm for 20 hours at room temperature to obtain composite powder F. Second Mixing Step: 0.72 g of composite powder F and 0.18 g of solid electrolyte C were placed in a 45 mL zirconia pot along with 34 g of 2 mm diameter zirconia balls and sealed. Using a tumbling mill ("Small Ball Mill Stand," manufactured by Asahi Rika Seisakusho, model number AV-1), mixing was carried out at a rotation speed of 600 rpm for 1 hour at room temperature to obtain a positive electrode composite powder. The obtained positive electrode composite powder was subjected to the same measurements and tests as in Example 5.

[0081] Comparative Example 3 0.54 g of composite powder A obtained in the same manner as in Example 1 and 0.36 g of solid electrolyte A obtained in the same manner as in Example 1 were placed in a 45 mL zirconia pot together with ten 10 mm diameter zirconia balls and sealed. Using a planetary ball mill (manufactured by Fritsch, model number P-7), mixing was carried out at a rotation speed of 370 rpm for 20 hours at room temperature to obtain a positive electrode composite powder. The obtained positive electrode composite powder was subjected to the same measurements and tests (except for SEM-EDS measurement) as in Example 5.

[0082] The results are shown in Table 4.

[0083]

[0084] (Example 7) 1. Preparation of Cathode Composite Material (1) Preparation of Solid Electrolyte C Solid electrolyte C was obtained in the same manner as in Example 5. (2) Preparation of Cathode Composite Powder First Mixing Step 0.7778 g of composite powder A and 0.2222 g of solid electrolyte A were placed in a 45 mL zirconia pot together with 10 zirconia balls having a diameter of 10 mm, and the pot was sealed. Using a planetary ball mill (manufactured by Fritsch, model number P-7), mixing was carried out at a rotation speed of 370 rpm for 20 hours at room temperature to obtain composite powder G. Second Mixing Step 0.81 g of composite powder G and 0.09 g of solid electrolyte C were placed in a 45 mL zirconia pot together with 34 g of zirconia balls having 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 a rotation speed of 600 rpm for 1 hour at room temperature to obtain a positive electrode composite powder.

[0085] 2. Measurement and Test Methods (1) Energy Dispersive X-ray Spectroscopy (SEM-EDS Analysis) of Electron Microscope Images and Calculation of the Overlap Rate of Carbon and Phosphorus SEM-EDS analysis was performed in the same manner as in Example 1, and the overlap rate was calculated. (2) Powder X-ray Diffraction (XRD) of Positive Electrode Composite Powder XRD measurement was performed in the same manner as in Example 1, and the half-width of diffraction peak B was calculated. (3) Test for Measuring Weight Loss Rate Upon Heating The same test as in Example 1 was performed.

[0086] (4) Evaluation of Battery Characteristics Preparation of Negative Electrode Composite An LTO negative electrode composite was obtained in the same manner as in Example 5. Preparation of Lithium-Ion Battery (All-Solid State) 100 mg of solid electrolyte A prepared by the above procedure was pressure-molded in a Macol cylinder with a diameter of 10 mm. The above-prepared positive electrode composite powder was placed on the pressurized surface so that the sulfur content was 5.88 mg, and the battery was again pressure-molded. 166 mg of LTO negative electrode composite was placed on the pressurized surface opposite the positive electrode composite and pressure-molded. A Li foil with a diameter of 9 mm and a thickness of 0.1 mm was placed on top of the mixture and pressure-molded again to prepare an all-solid-state battery. A constant-current charge-discharge test was performed on the obtained all-solid-state battery. The voltage range for the constant-current charge-discharge test was set to -0.4 to +1.3 V, and the current values ​​were as shown in Table 5 below. The discharge capacity (per sulfur mass) at 1 / 3 C was measured at the 6th cycle under the following conditions.

[0087]

[0088] Comparative Example 4 0.63 g of composite powder A obtained in the same manner as in Example 1 and 0.27 g of solid electrolyte A obtained in the same manner as in Example 1 were placed in a 45 mL zirconia pot together with ten 10 mm diameter zirconia balls and sealed. Using a planetary ball mill (manufactured by Fritsch, model number P-7), mixing was carried out at a rotation speed of 370 rpm for 20 hours at room temperature to obtain a positive electrode composite powder. The obtained positive electrode composite powder was subjected to the same measurements and tests (except for SEM-EDS measurement) as in Example 7.

[0089] The results are shown in Table 6.

[0090]

[0091] (Evaluation) In Examples 1 to 7, diffraction peaks A and B were confirmed, and the overlap rate of carbon and phosphorus was maintained at a high level. This indicates that the mixed state was good and the crystallinity of the solid electrolyte was maintained. As a result, the capacity under high current and high rate conditions (capacity at 1 C in Examples 1 to 4, capacity at 0.5 C in Examples 5 and 6, and capacity at 1 / 3 C in Example 7) was high, indicating excellent rate characteristics.

[0092] The positive electrode composite of the present invention is suitable for use as a positive electrode for a lithium ion battery. The lithium ion battery of the present invention is also 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.

[0093] Although several embodiments and / or examples of the present invention have been described in detail above, those skilled in the art will readily be able to make numerous modifications to these exemplary embodiments and / or examples without substantially departing from the novel teachings and advantages of the present invention. Accordingly, these numerous modifications are within the scope of the present invention. The contents of all documents cited in this specification and of the applications from which this application claims priority under the Paris Convention are incorporated by reference in their entirety.

Claims

1. The battery includes a conductive additive that is a carbon material, a sulfur-based active material, and a solid electrolyte, In elemental analysis by energy dispersive X-ray spectroscopy of electron microscope images, the overlap rate of carbon and phosphorus mapping is 50% or more; A positive electrode composite having a diffraction peak A at 2θ=20.2±0.5° and a diffraction peak B at 2θ=41.1±0.8° in powder X-ray diffraction using CuKα radiation.

2. The positive electrode mixture according to claim 1 , wherein the half width of the diffraction peak B is 1.15° or less.

3. 3. The positive electrode mixture according to claim 1, wherein the solid electrolyte contains lithium atoms, phosphorus atoms, sulfur atoms, bromine atoms, and iodine atoms.

4. 3. The positive electrode mixture according to claim 1, wherein the weight loss rate when heat-treated at 190°C for 2 hours is 2.5% or more.

5. 3. The positive electrode mixture according to claim 1, wherein the weight loss rate of the sulfur-based active material when heat-treated at 190°C for 2 hours is 7.0% or more.

6. 3. The cathode composite according to claim 1, wherein the cathode composite is obtained by a production method including: a first mixing step of adding a solid electrolyte to a sulfur-based active material and performing a mixing process to obtain a first mixture; and a second mixing step of adding a further solid electrolyte to the first mixture and performing a mixing process to obtain a second mixture, wherein the second mixing step uses less energy than the first mixing step.

7. the first mixing step is performed under conditions in which the solid electrolyte added in the first mixing step is made amorphous; The second mixing step is performed under conditions such that the crystallinity of the solid electrolyte added in the second mixing step is not lost. The positive electrode mixture according to claim 6 .

8. a first mixing step of adding a solid electrolyte to a sulfur-based active material and mixing the mixture to obtain a first mixture; a second mixing step of adding a further solid electrolyte to the first mixture and performing a mixing process thereon to obtain a second mixture; The method for producing a positive electrode composite, wherein the second mixing step is performed with less energy than the first mixing step.

9. the first mixing step is performed under conditions in which the solid electrolyte added in the first mixing step is made amorphous; The second mixing step is performed under conditions such that the crystallinity of the solid electrolyte added in the second mixing step is not lost. The method for producing a positive electrode mixture according to claim 8 .

10. The method for producing the positive electrode mixture according to claim 8 or 9, which produces the positive electrode mixture according to claim 1 or 2.

11. A lithium ion battery comprising the positive electrode mixture according to claim 1 or 2.