Composite particles for electrodes and method for manufacturing the same

Abstract

To provide a composite material for an electrode that is excellent in performance as an electrode and is also excellent in productivity while using sulfur.SOLUTION: Composite particles for an electrode include a crystalline phase of sulfur, and carbon particles dispersed within the crystalline phase, and the carbon particles have a volume average particle diameter (D50) in the range of 1 to 999 nm, the carbon particles have amorphous sulfur on the surface and / or inside of the carbon particles, and the composite particles volume average particle size (D50) is in the range of 1 to 1000 μm.SELECTED DRAWING: Figure 12

Description

[Technical Field]

[0001] This invention relates to electrode composite particles, electrode active materials, electrodes, secondary batteries, and methods for producing electrode composite particles. More specifically, it relates to electrode composite particles comprising a crystalline sulfur phase and carbon particles dispersed in the crystalline phase. [Background technology]

[0002] In recent years, the demand for lithium-ion secondary batteries for storing electricity has been increasing in vehicles such as electric vehicles (EVs) and hybrid vehicles, as well as in power generation equipment such as solar cells and wind turbines. Furthermore, from the perspective of ensuring safety, all-solid-state batteries that use a solid electrolyte instead of a liquid electrolyte layer are being actively researched. These lithium-ion secondary batteries and all-solid-state batteries are required to be even more high-performance. Many all-solid-state batteries under development use metal oxides as the positive electrode active material, but considering the energy storage capacity required for EVs and the like, there is a need to use active material materials with a larger theoretical capacity. Among these, the use of sulfur as an active material is attracting attention.

[0003] Sulfur has a large theoretical capacity (1672 mAh g) -1 Because it possesses these properties, it is expected to be used as an active material for next-generation all-solid-state batteries. However, because sulfur has low electronic and ionic conductivity, it cannot be used alone as an electrode active material. Attempts have been made to utilize sulfur, and for example, Japanese Patent Publication No. 2010-095390 (Patent Document 1) and Japanese Patent Publication No. 2020-161288 (Patent Document 2) disclose composites in which sulfur is deposited on carbon particles. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2010-095390 [Patent Document 2] Japanese Patent Publication No. 2020-161288 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] While there are several reports on composite materials for electrodes that use sulfur as an electrode active material, such as the methods mentioned above, the performance of batteries using these reported composite materials remains low. Therefore, the challenge is to provide a composite material for electrodes that uses sulfur while exhibiting excellent electrode performance. [Means for solving the problem]

[0006] As a result of diligent research, the inventors of the present invention discovered that, in order to impart electronic conductivity to insulating sulfur, carbon particles, which have excellent electronic conductivity, can be added as a conductive additive, and that by further heating and kneading these in a twin-screw fusion kneader, composite particles for electrodes with excellent properties as electrode materials can be produced, leading to the present invention. Thus, the present invention provides a composite particle for electrodes comprising a crystalline sulfur phase and carbon particles dispersed within the crystalline phase, wherein the volume average particle diameter (D 50 The diameter is in the range of 1 to 999 nm, and the carbon particles have amorphous sulfur on the surface and / or inside the carbon particles, and the volume average particle diameter (D) of the composite particles 50 ) provides electrode composite particles in the range of 1 to 1000 μm. Furthermore, the present invention provides an electrode active material containing the above-mentioned electrode composite particles, an electrode, and a secondary battery. Furthermore, the present invention provides a method for producing composite particles for electrodes, comprising the step of heating and kneading a sulfur composition and carbon particles in a twin-screw fusion kneader. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an electrode composite material that has excellent performance as an electrode while still using sulfur. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic diagram of a twin-screw fusion kneader. [Figure 2] This graph shows the results of charge-discharge tests performed on half-cells using the electrode composite particles of Example 1 or the sample of Comparative Example 1. [Figure 3A] This graph shows the results of charge-discharge tests performed on half-cells using the electrode composite particles of Examples 2-4. [Figure 3B] This graph shows the results of charge-discharge tests performed on half-cells using the electrode composite particles of Examples 2, 5, and 6. [Figure 3C] This graph shows the results of charge-discharge tests performed on half-cells using the electrode composite particles of Example 2, 10, or 11. [Figure 4A] This is an SEM image of the sample from Comparative Example 5. [Figure 4B] This is an SEM image of the composite particles for the electrode in Example 2. [Figure 5A] These are SEM images of the electrode composite particles from Examples 2-4. [Figure 5B] These are SEM images of the electrode composite particles from Examples 2, 5, and 6. [Figure 6A] This is a SEM image of sulfur. [Figure 6B] This is a SEM image of carbon particles. [Figure 6C] This is an SEM image of LPS. [Figure 7A] This graph shows the particle size distribution of the electrode composite particles from Examples 2-4 and the sample from Comparative Example 5. [Figure 7B] This graph shows the particle size distribution of the electrode composite particles from Examples 2, 5, and 6 and the sample from Comparative Example 5. [Figure 7C] This graph shows the particle size distribution of the composite particles for electrodes in Example 10 and the sample in Comparative Example 6. [Figure 7D] This graph shows the particle size distribution of the composite particles for electrodes in Example 11 and the sample in Comparative Example 7. [Figure 8A] This graph shows the nitrogen adsorption isotherms of the electrode composite particles from Examples 2-4 and the sample from Comparative Example 5. [Figure 8B] This graph shows the nitrogen adsorption isotherms of the electrode composite particles from Examples 2, 5, and 6 and the sample from Comparative Example 5. [Figure 8C] This graph shows the nitrogen adsorption isotherms of the composite particles for the electrodes in Example 6 and the samples in Comparative Examples 4 and 5. [Figure 8D] This graph shows the nitrogen adsorption isotherms of the electrode composite particles from Examples 2, 10, and 11 and the samples from Comparative Examples 5 to 7. [Figure 9A] This graph shows the results of XRD measurements of the electrode composite particles from Example 6 and the sample from Comparative Example 5. [Figure 9B] This graph shows the results of XRD measurements of the electrode composite particles from Example 6 and the sample from Comparative Example 1. [Figure 10A] This image shows the angle of repose of the electrode composite particles in Example 6. [Figure 10B] This image shows the angle of repose of the sample in Comparative Example 5. [Figure 11A] This is an SEM-EDX image of the electrode composite particles from Example 6. [Figure 11B] This is the SEM-EDX image of the sample from Comparative Example 5. [Figure 12] This graph shows the results of charge-discharge tests performed on half-cells using the electrode composite particles of Example 7 or the sample of Comparative Example 1. [Figure 13] This graph shows the results of varying the charge-discharge rate of a half-cell using the electrode composite particles of Example 7 or the sample of Comparative Example 1. [Figure 14] This graph shows the charge-discharge capacity for each charge-discharge cycle of a half-cell using the electrode composite particles of Example 7 or the sample of Comparative Example 1. [Figure 15] This graph shows the charge and discharge capacities of half-cells using the electrode composite particles of Examples 7-9 or the samples of Comparative Examples 1-3. [Figure 16] This graph shows the results of impedance measurements performed on half-cells using the electrode composite particles of Examples 7-9 or the samples of Comparative Examples 1-3. [Figure 17] This is a schematic diagram of an electron blocking cell. [Modes for carrying out the invention]

[0009] (Composite particles for electrodes) The composite particles for electrodes of the present invention comprise a crystalline phase of sulfur and carbon particles dispersed within the crystalline phase. The composite particles for electrodes have a volume average particle diameter (D 50 ) in the range of 1 to 1000 μm. In the present invention, the volume average particle diameter is based on the volume-based particle diameter distribution measured using a laser diffraction / scattering particle size distribution measuring device. Examples of the laser diffraction / scattering particle size distribution measuring device include "SALD-2100" manufactured by Shimadzu Corporation, "Aerotrack LDSA-SPR" of Microtrac Bell Co., Ltd., "Mastersizer 3000" of Malvern Panalytical, etc. The volume average particle diameter (D 50 ) is also called the volume median diameter and is the particle diameter at which the frequency cumulative becomes 50% in the volume-based particle diameter distribution. That is, particles having a particle diameter of less than or equal to the value of D 50 occupy 50% of the total volume. Similarly, D 10 is the particle diameter at which the frequency cumulative becomes 10% in the volume-based particle diameter distribution, and D 90 is the particle diameter at which the frequency cumulative becomes 90% in the volume-based particle diameter distribution.

[0010] The volume average particle diameter (D 50The range is, for example, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 16.9, 17, 20, 25, 30, 34, 34.7, 35, 40, 45, 50, 55, 58, 60, 60.3, 64.1, 64.8, 65, 66.1, 67, 70, 75, 80, 85, 90, 95, 99, 100, 110, 120, 125, 150, 175, 200, 225, 250, 300, 350, The range can be expressed as any combination of upper and lower limits selected from the values ​​of 400, 450, 499, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 975, 990, 999, or 1000 μm. Volume average particle diameter (D) of composite particles for electrodes. 50 The ) is preferably in the range of 1 to 999 μm, more preferably in the range of 1 to 900 μm, more preferably in the range of 1 to 700 μm, more preferably in the range of 1 to 500 μm, more preferably in the range of 1 to 400 μm, more preferably in the range of 1 to 300 μm, more preferably in the range of 1 to 200 μm, more preferably in the range of 1 to 100 μm, more preferably in the range of 10 to 100 μm, more preferably in the range of 25 to 100 μm, and more preferably in the range of 50 to 100 μm.

[0011] Volume-average particle diameter (D) of composite particles for electrodes 10The range is, for example, 0.5, 1.0, 1.5, 2.0, 2.5, 3, 3.5, 4, 4.11, 4.5, 5.0, 5.21, 5.25, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 9.9, 10, 10.1, 10.5, 11, 12, 12.5, 13, 13.5, 13.9, 14, 14.1, 14.2, 14.3, 14.4, 14.5, 14.6, 15, 15.2, 15.3, 15.4, 15.5, 16, 17, 18, 19, 20, The range can be expressed as any combination of upper and lower limits selected from the values ​​of 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 35, 40, 45, 49, 50, 51, 55, 60, 65, 70, 75, 80, 85, 90, 95, 98, 99, 99.9 or 100 μm. Volume average particle diameter (D) of composite particles for electrodes. 10 The ) is in the range of 0.5 to 100 μm, preferably in the range of 0.5 to 90 μm, more preferably in the range of 0.5 to 80 μm, more preferably in the range of 0.5 to 70 μm, more preferably in the range of 0.5 to 60 μm, more preferably in the range of 0.5 to 50 μm, more preferably in the range of 1 to 50 μm, more preferably in the range of 1 to 40 μm, more preferably in the range of 5 to 40 μm, more preferably in the range of 5 to 30 μm, more preferably in the range of 10 to 30 μm, and more preferably in the range of 10 to 20 μm.

[0012] Volume-average particle diameter (D) of composite particles for electrodes 90The range is, for example, 5, 6, 7, 8, 9, 10, 11, 15, 20, 25, 30, 35, 40, 50, 55, 60, 65, 70, 74, 74.9, 75, 80, 85, 90, 95, 99, 100, 101, 105, 110, 120, 130, 140, 145, 150, 155, 158, 159, 160, 165, 170, 175, 180, 185, 190, 195, 196, 197, 198, 199, 200, 205, 208, 210, 220, 225, 229, 230, 240, 245, 248, 249, 250, 260, 275, 300, 325, 350, 375, 400, 425, 450, 475, 490, 499, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 980, 990, 999, 1000, 1100, 1200, 1250, 1300, 1400, 1500, 1600, 1700, 1750, 1800, The range can be expressed as any combination of upper and lower limits selected from the values ​​of 1900, 1950, 1990, 1999, or 2000 μm. Volume average particle diameter (D) of composite particles for electrodes 90) is in the range of 5 to 2000 μm, preferably in the range of 5 to 1750 μm, more preferably in the range of 5 to 1500 μm, more preferably in the range of 5 to 1250 μm, more preferably in the range of 5 to 1000 μm, more preferably in the range of 5 to 999 μm, more preferably in the range of 5 to 900 μm, more preferably in the range of 5 to 800 μm, more preferably in the range of 5 to 700 μm, more preferably in the range of 5 to 600 μm, and more preferably in the range of 5 to 500 μm. Preferably, the range is 10 to 500 μm, more preferably 20 to 500 μm, more preferably 30 to 500 μm, more preferably 40 to 500 μm, more preferably 50 to 500 μm, more preferably 60 to 500 μm, more preferably 70 to 500 μm, more preferably 80 to 500 μm, more preferably 90 to 500 μm, and more preferably 100 to 500 μm.

[0013] As mentioned above, D 10 , D 50 and D 90 The combination is the volume-average particle diameter (D 10 ) is in the range of 0.5 to 50 μm, and the volume average particle size (D 50 ) is in the range of 1 to 100 μm, and the volume average particle size (D 90 Preferably, the volume average particle diameter (D) is in the range of 5 to 500 μm. 10 ) is in the range of 10-20 μm, and the volume average particle size (D 50 ) is in the range of 50-100 μm, and the volume average particle size (D 90 It is more preferable that the particle size is in the range of 100 to 500 μm. By using composite particles for electrodes with such particle size ranges, electrodes with superior charge-discharge characteristics can be obtained.

[0014] The crystalline phase of sulfur includes not only the state of elemental sulfur alone, but also the state in which metal sulfides are finely dispersed in the crystalline phase. Examples of metal sulfides include TiS2, MoS2, FeS, FeS2, CuS, Ni3S2, and NbSe3. The amount of finely dispersed metal sulfides is preferably 5% by mass or less, more preferably 4% by mass or less, more preferably 3% by mass or less, more preferably 2% by mass or less, more preferably 1% by mass or less, more preferably 0.5% by mass or less, more preferably 0.3% by mass or less, and more preferably 0.1% by mass or less, based on the total mass of the composite particles for the electrode.

[0015] The proportion of sulfur in the electrode composite particles is not particularly limited, but it is preferably in the range of 20% to 90% by mass, and more preferably in the range of 30% to 80% by mass, relative to the total mass of the electrode composite particles.

[0016] The carbon particles are dispersed within the crystalline sulfur phase. The proportion of carbon particles in the electrode composite particles is not particularly limited, but it is preferably in the range of 5% to 60% by mass, and more preferably in the range of 10% to 50% by mass, relative to the total mass of the electrode composite particles.

[0017] Volume-average particle diameter of carbon particles (D 50 ) is in the range of 1 to 999 nm. Volume average particle diameter (D) of carbon particles 50The range is, for example, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 22.5, 25, 27.5, 30, 32.5, 34, 35, 37.5, 40, 42.5, 45, 47.5, 50, 55, 60, 65, 70, 80, 90, 99, 100, 110, 125, 150, 175, 200, 225, 250, 300, 350, 400, 450, 499, The range can be expressed as any combination of upper and lower limits selected from the values ​​of 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 975, 990, or 999 nm. (Volume average particle diameter of carbon particles (D)) 50 The wavelength is preferably in the range of 1 to 900 nm, more preferably in the range of 1 to 800 nm, more preferably in the range of 1 to 700 nm, more preferably in the range of 1 to 600 nm, more preferably in the range of 1 to 500 nm, more preferably in the range of 1 to 400 nm, more preferably in the range of 1 to 300 nm, more preferably in the range of 1 to 200 nm, more preferably in the range of 1 to 100 nm, more preferably in the range of 10 to 100 nm, and more preferably in the range of 10 to 50 nm.

[0018] The structure of the carbon particles is not particularly limited; they may be solid or porous, but porous carbon particles are preferred. Whether or not the carbon particles have pores can be confirmed, for example, by SEM (scanning electron microscope). Alternatively, porous carbon particles may be defined as carbon particles with a nitrogen adsorption capacity of 100 ml(STP) / g or more. In this invention, nitrogen adsorption capacity refers to the nitrogen adsorption capacity when the P / P0 of the nitrogen adsorption isotherm is 0.98, measured using nitrogen gas at liquid nitrogen temperature (77K) with a relative pressure (P / P0) in the range of 0 to 1. Porous carbon particles preferably have a nitrogen adsorption capacity of 500 ml(STP) / g or more, more preferably 750 ml(STP) / g or more, more preferably 1000 ml(STP) / g or more, and more preferably 1200 ml(STP) / g or more.

[0019] The carbon particles contained in the electrode composite particles may be mainly porous carbon particles. "Mainly porous carbon particles" means that more than 50% by mass of the carbon particles contained in the electrode composite particles are porous carbon particles. Preferably, 60% or more by mass of the carbon particles contained in the electrode composite particles are porous carbon particles; more preferably, 70% or more by mass are porous carbon particles; more preferably, 80% or more by mass are porous carbon particles; more preferably, 90% or more by mass are porous carbon particles; more preferably, 95% or more by mass are porous carbon particles; more preferably, 98% or more by mass are porous carbon particles; more preferably, 99% or more by mass are porous carbon particles; and more preferably, 99.9% or more by mass are porous carbon particles. Furthermore, it is preferable that the carbon particles contained in the electrode composite particles are substantially porous carbon particles. "Substantially porous carbon particles" means that a small amount of non-porous carbon particles are included among the porous carbon particles.

[0020] Examples of carbon particles include nanocarbon or fibrous carbon (e.g., vapor-grown carbon fibers (VGCF) or carbon nanofibers), and more specifically, natural graphite, artificial graphite, acetylene black, Ketjen black, and furnace black. The composite particles for electrodes may contain only one type of carbon particle or a combination of multiple types.

[0021] Amorphous sulfur is contained on the surface and / or inside the carbon particles contained within the crystalline phase of sulfur. Preferably, amorphous sulfur is contained in the pores of the carbon particles. Being amorphous is the same as what is generally recognized as amorphous by those skilled in the art, and refers to a state that does not have clear crystallinity. The state of not having clear crystallinity can be confirmed, for example, by the absence of a peak in XRD (X-ray diffraction) using CuKα rays, or by the fact that the 2θ peak originating from sulfur in the XRD does not have a full width at half maximum (FMAX) of 2° or more. It can also be confirmed by the absence of clear crystallites using a transmission electron microscope. Amorphous sulfur includes not only a state that is 100% amorphous, but also a state that is substantially amorphous. Sulfur being substantially amorphous includes the case in which crystalline sulfur is finely dispersed in amorphous sulfur.

[0022] The nitrogen adsorption amount of the electrode composite particles is not particularly limited, but it is preferable that the nitrogen adsorption amount of the electrode composite particles is 50% or less of the nitrogen adsorption amount of the carbon particles contained in the electrode composite particles (in a state where sulfur is not present on its surface and / or inside), more preferably 45% or less, and even more preferably 40% or less. Furthermore, it is particularly preferable that the nitrogen adsorption amount of the carbon particles contained in the electrode composite particles is 1000 ml (STP) / g or more, and that the nitrogen adsorption amount of the electrode composite particles is 50% or less of the nitrogen adsorption amount of the carbon particles contained in the electrode composite particles (in a state where sulfur is not present on its surface and / or inside).

[0023] The mass ratio of sulfur to carbon particles is not particularly limited, but it is preferably in the range of sulfur:carbon particles = 1.0:0.1 to 1.0, more preferably in the range of sulfur:carbon particles = 1.0:0.1 to 0.5, and even more preferably in the range of sulfur:carbon particles = 1.0:0.1 to 0.4.

[0024] The composite particles for electrodes preferably have an angle of repose of 50° or less, and more preferably 45° or less. Here, the angle of repose in this invention is the angle that the surface of the stationary powder layer makes with the horizontal plane when the powder discharged from the funnel in a gravitational field accumulates and forms a free surface. The angle of repose can be measured, for example, using a multi-tester model MT-1001k manufactured by Seishin Corporation.

[0025] The electrode composite particles may further contain solid electrolyte particles. The solid electrolyte of the solid electrolyte particles is not particularly limited and may be a sulfide-based solid electrolyte or an oxide-based solid electrolyte, but a sulfide-based solid electrolyte is preferred. Examples of sulfide-based solid electrolytes include Li3PS4, Li2S-P2S5, Li2S-P2S5-LiI, Li2S-P2S5-LiCl, Li2S-P2S5-LiI-LiBr, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-GeS2, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, Li 10 GeP2S 12 Li7P3S 11 Li 3.25 P 0.75 S4 or Li 7-x PS 6-x Y x Examples include (where x is between 0 and 1.8, and Y is a halogen). Examples of oxide-based solid electrolytes include Li2O-B2O3-P2O3, Li2O-SiO2, Li2O-P2O5, and Li5La3Ta2O.12 Li7La3Zr2O 12 Li6BaLa2Ta2O 12 Li 3.6 Si 0.6 P 0.4 Examples include O4 or Li3BO3-Li2SO4-Li2CO3. The solid electrolyte particles may consist of a single type of solid electrolyte, or they may be solid electrolyte particles composed of a combination of multiple solid electrolytes. The solid electrolyte particles may consist of only one type, or a combination of multiple types. The solid electrolyte may be amorphous or not, but it is preferable that it be substantially amorphous. A solid electrolyte being substantially amorphous includes cases where crystalline solid electrolytes are finely dispersed in an amorphous solid electrolyte.

[0026] Volume-average particle diameter (D) of solid electrolyte particles 50 ) is not particularly limited, but the volume-average particle diameter (D) of the solid electrolyte particles. 50 The range is, for example, 0.01, 0.05, 0.07, 0.09, 0.1, 0.15, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.99, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 7, 8, 8.4, 8.5, 8.6, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 22.5, 25, 27.5, 30, 32.5, 34, 35, 37.5, 40, 42.5, 45, 47.5, The range can be expressed by any combination of upper and lower limits selected from the values ​​of 49 or 50 μm. (D) 50 The particle size is preferably in the range of 0.01 to 50 μm, more preferably in the range of 0.01 to 40 μm, and even more preferably in the range of 0.01 to 30 μm.

[0027] The mass ratio of sulfur and carbon particles to solid electrolyte particles is not particularly limited, but it is preferable that the mass ratio of sulfur and carbon particles to solid electrolyte particles is in the range of sulfur + carbon particles:solid electrolyte = 1.0:0.1 to 1.0, more preferably in the range of sulfur + carbon particles:solid electrolyte = 1.0:0.3 to 1.0, and even more preferably in the range of sulfur + carbon particles:solid electrolyte = 1.0:0.5 to 1.0.

[0028] The composite particles for electrodes have a BET specific surface area of ​​200 m². 2 It is preferable that the value is less than or equal to / g. The BET specific surface area can be obtained using the BET adsorption isotherm (Brunauer Emmrtt Teller adsorption isotherm), which is known for nitrogen adsorption isotherms. The BET specific surface area is 180m². 2 It is preferable that it be less than or equal to / g, and 160m 2 It is more preferable that it be less than or equal to / g, and 150m 2 It is more preferable that it be less than or equal to / g, and 125m 2 It is more preferable that it be less than or equal to / g, and 100m 2 It is more preferable that it be less than or equal to / g, 90m 2 It is more preferable that it be less than or equal to / g, 80m 2 It is more preferable that it be less than or equal to / g, 70m 2 It is more preferable that it be less than or equal to / g, 60m 2 It is more preferable that it be less than or equal to / g, 50m 2 It is more preferable that it be less than or equal to / g, 40m 2 It is more preferable that it be less than or equal to / g, 30m 2 It is more preferable that it be less than or equal to / g, 25m 2 It is more preferable that it be less than or equal to / g, 20m 2 It is more preferable that it be less than or equal to / g, 15m 2 It is more preferable that it be less than or equal to / g, 10m 2 It is more preferable that the value be less than or equal to / g.

[0029] Total pore volume V of composite particles for electrodes t (cm 3 / g) is not particularly limited, but 0.5 (cm3 It is preferable that it is less than or equal to 0.45 (cm³) 3 It is more preferable that it be less than or equal to 0.43 (cm³) 3 It is more preferable that it be less than or equal to 0.4 (cm 3 It is more preferable that it be less than or equal to 0.3 (cm) 3 It is more preferable that it be less than or equal to 0.25 (cm³) 3 It is more preferable that it be less than or equal to 0.2 (cm) 3 It is more preferable that it be less than or equal to 0.1 (cm) 3 It is more preferable that it be less than or equal to 0.09 (cm³) 3 It is more preferable that it be less than or equal to 0.08 (cm³) 3 It is more preferable that it be less than or equal to 0.07 (cm³) 3 It is more preferable that it be less than or equal to 0.0691 (cm³ / g), 3 It is more preferable that it be less than or equal to 0.05 (cm³) / g. 3 It is more preferable that it be less than or equal to 0.04 (cm³) 3 It is more preferable that the total pore volume V is less than or equal to / g. t This can be calculated by using the known BJH (Barrett-Joyner-Halenda) equation for nitrogen adsorption isotherms.

[0030] The electrode composite particles may further contain a binder. The binder is not particularly limited as long as it is a binder commonly used in the field. Examples of binders include fluorine polymers, polyolefin polymers, poly(meth)acrylic polymers, polyvinyl polymers, polystyrene polymers, polyimide polymers, polyester polymers, cellulose polymers, and polyacrylonitrile polymers. Specific examples include polyvinylidene fluoride (PVDF), polytetrafluoroethylene, polyvinyl alcohol, polyvinyl acetate, polymethyl methacrylate, polyethylene, polypropylene, styrene-butadiene rubber, acrylonitrile-butadiene rubber, polyimide, polyamide, carboxymethylcellulose, polyacrylonitrile, and copolymers thereof. The binder may be included in an amount of 20% by mass or less of the electrode composite particles, preferably 15% by mass or less, more preferably 10% by mass or less, more preferably 5% by mass or less, more preferably 3% by mass or less, and more preferably 1% by mass or less.

[0031] (Method for manufacturing composite particles for electrodes) One embodiment of the present invention provides a method for producing composite particles for electrodes, comprising the step of heating and kneading a sulfur composition and carbon particles in a twin-screw fusion kneader. Another embodiment of the present invention provides a method for producing composite particles for electrodes, comprising the step of heating and kneading a sulfur composition and carbon particles in a twin-screw fusion kneader, and the step of adding and mixing solid electrolyte particles after heating and kneading. The carbon particles used in the production of the composite particles for electrodes are as described above. The sulfur composition referred to here is one that contains sulfur and metal sulfides. Examples of metal sulfides include TiS2, MoS2, FeS, FeS2, CuS, Ni3S2, and NbSe3. The amount of metal sulfides is preferably 5% by mass or less, more preferably 4% by mass or less, more preferably 3% by mass or less, more preferably 2% by mass or less, more preferably 1.5% by mass or less, more preferably 1% by mass or less, more preferably 0.8% by mass or less, more preferably 0.5% by mass or less, more preferably 0.3% by mass or less, more preferably 0.2% by mass or less, and more preferably 0.1% by mass or less, based on the total mass of the sulfur composition.

[0032] Figure 1 shows a schematic diagram of a twin-screw fusion kneading apparatus. A twin-screw fusion kneading apparatus consists of a barrel with controllable heating and two parallel screws inside the barrel, allowing it to apply a stronger shear force to the sample than a single-screw kneading apparatus. Furthermore, by applying heat to the barrel, it is possible to continuously knead the sample while heating it. The twin-screw fusion kneading apparatus may also be equipped with additional devices such as a hopper. By adding a sulfur composition and carbon particles to a twin-screw fusion kneader and heating and kneading, the sulfur and carbon particles can be kneaded together while melting the sulfur. The temperature during heating and kneading is not particularly limited as long as it does not exceed the boiling point of sulfur, but is preferably in the range of 120°C to 400°C, more preferably in the range of 120°C to 300°C, more preferably in the range of 120°C to 250°C, more preferably in the range of 120°C to 200°C, and more preferably in the range of 140°C to 200°C. The rotational speed of the screw is not particularly limited, but can be set in the range of, for example, 1 rpm to 400 rpm. The diameter of the screw is also not particularly limited and may vary depending on the size of the twin-screw fusion mixing apparatus, but can be set in the range of, for example, 0.5 mm to 50 mm. The shape of the screw is also not particularly limited. After collecting the sample that has undergone twin-screw fusion mixing, it may be added back to the twin-screw fusion mixing apparatus and subjected to the same treatment again.

[0033] When using a twin-screw fusion kneader, a solid electrolyte may be added in addition to the sulfur composition and carbon particles. The solid electrolyte described above can be used. The composite particles for electrodes, after processing in a twin-screw fusion kneader, may be further mixed using a ball mill. Examples of ball mills include planetary ball mills. For example, when using a planetary ball mill, conditions such as a ball diameter of 4 to 10 mm, a rotation speed of 50 to 600 rpm, a processing time of 0.1 to 100 hours, and a filtration rate of 1 to 100 kWh per kg of raw material may be used. Examples of ball materials include zirconia. After processing the electrode composite particles in a twin-screw fusion kneader, a solid electrolyte may be added and the mixture may be further mixed using a ball mill. The conditions for the ball mill are as described above. When producing electrode composite particles containing sulfur, carbon particles, and a solid electrolyte, it is preferable to perform twin-screw fusion kneading on the sulfur and carbon particles first, and then add the solid electrolyte and mix, for example, using a ball mill, rather than adding the sulfur, carbon particles, and solid electrolyte to the twin-screw fusion kneader and processing them together.

[0034] (electrode active material) The present invention provides an electrode active material containing the electrode composite particles of the present invention. The electrode active material may consist only of the electrode composite particles of the present invention, but may also contain a binder, a conductive material, a solid electrolyte, etc. The binder and solid electrolyte are as described above. The electrode active material preferably contains the electrode composite particles of the present invention as its main component. Containing as a main component means that the electrode composite particles are present in an amount greater than 50% by mass relative to the total mass of the electrode active material. The mass percentage of the electrode composite particles is preferably 60% by mass or more, more preferably 70% by mass or more, more preferably 75% by mass or more, more preferably 80% by mass or more, more preferably 90% by mass or more, and more preferably 95% by mass or more, relative to the total mass of the electrode active material.

[0035] Conductive materials mainly consist of carbon-based conductive materials and metallic conductive materials. Examples of carbon-based conductive materials include the carbon particles mentioned above. Examples of metallic conductive materials include metals such as Cu, Ni, Al, Ag, Au, Pt, Zn, or Mn, or alloys thereof. Of these, carbon-based conductive materials are preferred. The conductive material may be a single type of conductive material or a combination of multiple conductive materials.

[0036] The content range of binders, conductive materials, and solid electrolytes other than the electrode composite particles in the electrode active material can be expressed as any combination of upper and lower limits selected from 40% by mass, 35% by mass, 30% by mass, 25% by mass, 20% by mass, 15% by mass, 10% by mass, 8% by mass, 6% by mass, 5% by mass, 4% by mass, 3% by mass, 2.5% by mass, 2% by mass, 1.5% by mass, 1% by mass, 0.75% by mass, 0.5% by mass, 0.4% by mass, 0.3% by mass, 0.2% by mass, and 0.1% by mass, respectively. The content of binders, conductive materials, and solid electrolytes in the electrode active material is 40% by mass or less of the total mass of the electrode active material, preferably 35% by mass or less, more preferably 30% by mass or less, more preferably 20% by mass or less, and more preferably 10% by mass or less. However, the sum of the content of the binder, conductive material and solid electrolyte is preferably not more than 50% by mass, more preferably less than 40% by mass, more preferably less than 35% by mass, more preferably less than 30% by mass, more preferably less than 30% by mass, more preferably less than 25% by mass, more preferably less than 20% by mass, more preferably less than 15% by mass, more preferably less than 10% by mass, more preferably less than 7.5% by mass, and more preferably less than 5% by mass.

[0037] (electrode) The present invention provides an electrode comprising the electrode composite particles of the present invention or the electrode active material of the present invention as described above. The electrode may consist only of the electrode composite particles of the present invention or the electrode active material of the present invention as described above, but may further contain a binder, a conductive material, a solid electrolyte, an electrode active material, etc. The binder, conductive material, and solid electrolyte are as described above. The electrode of the present invention may be either a positive electrode or a negative electrode, but is preferably a positive electrode. The electrode preferably contains the electrode composite particles of the present invention as a main component. Containing as a main component means that the electrode composite particles make up more than 50% by mass relative to the total mass of the electrode. The mass percentage of the electrode composite particles is preferably 60% by mass or more, more preferably 70% by mass or more, more preferably 75% by mass or more, more preferably 80% by mass or more, more preferably 90% by mass or more, and more preferably 95% by mass or more, relative to the total mass of the electrode.

[0038] If necessary, an electrode active material other than the electrode active material of the present invention may be added to the electrode of the present invention. For example, if the electrode is a positive electrode, Li4Ti5O 12 , LiCoO2, LiMnO2, LiVO2, LiCrO2, LiNiO2, Li2NiMn3O8, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 Examples of negative electrode active materials include O2, LiFeO2, Li3V2(PO4)3, or LiMn2O4. If the electrode is a negative electrode, examples of negative electrode active materials include carbon-based materials such as natural graphite, artificial graphite, acetylene black, Ketjen black, furnace black, or VGCF, Si, Li alloys, Na alloys, metals such as Au, Pt, Pd, Ag, Al, Bi, Sn, Sb, Zn, Mg, K, Ca, or Na, and Li 4 / 3 Ti 5 / 3 Examples include various transition metal oxides such as O4, Li3V2(PO4)3, or SnO. These negative electrode active materials may be used individually or in combination of two or more. The content of the electrode active material is preferably 20% by mass or less of the total mass of the electrode, and more preferably 10% by mass or less. The electrodes may be coated with materials such as LiNbO3, NaNbO3, Al2O3, or NiS. These electrodes may be used individually or in combination of two or more types.

[0039] The electrodes can be obtained, for example, by mixing an electrode active material with an optional binder, conductive material, or electrolyte, and then pressing the resulting mixture into pellets. The pressing pressure may be selected from a range of, for example, 50-2000 MPa.

[0040] (electrode complex) The present invention also provides an electrode composite in which an electrode (preferably a positive electrode) and a current collector are combined. The electrode combined with the current collector is the electrode of the present invention described above. The current collector is not particularly limited in material, shape, etc., as long as it can be combined with the electrodes of the present invention and perform its function as a current collector. The shape of the current collector may be a uniform alloy plate or a shape with holes. It may also be in the form of foil, sheet, or film.

[0041] Examples of materials for the current collector include Al, Ni, Cu, Ti, Fe, Co, Ge, Cr, Mo, W, Ru, Pd, stainless steel, or steel. In addition to the above materials, the current collector may be coated with either Au or Al. The thickness of the coating is not particularly limited, but is preferably 10 nm to 100 μm. Furthermore, it is preferable that the coating has a uniform thickness. The coating method is not particularly limited as long as it can coat the current collector, but for example, it can be formed by depositing a coating onto the surface using a sputter coater. The electrode composite of the present invention may be formed by combining electrodes and current collectors, or electrodes may be formed directly on the current collector. In the case of direct formation, an electrode active material may be applied to the surface of the current collector using a known method.

[0042] (Secondary battery) The present invention provides a secondary battery comprising the electrode or electrode composite of the present invention. The secondary battery may be a general lithium-ion secondary battery or an all-solid-state secondary battery. The electrode of the present invention can be used as either the positive electrode or the negative electrode. When the electrode of the present invention is used as the positive electrode, the negative electrode is not particularly limited as long as Li can exchange with the positive electrode as mobile ions during charging and discharging. Such a negative electrode is preferably one with a low oxidation-reduction potential, and more preferably one with an average charge-discharge potential of 0.7V or less relative to the oxidation-reduction potential of Li. Furthermore, when the electrode of the present invention is used as the negative electrode, the positive electrode is not particularly limited as long as Li can exchange with the negative electrode as mobile ions during charging and discharging. Such a positive electrode is preferably one with a high oxidation-reduction potential, and more preferably one with an average charge-discharge potential of 3.5V or more relative to the oxidation-reduction potential of Li. The electrode active materials used in the positive and negative electrodes may consist of the above-mentioned electrode active materials. The positive and negative electrodes that can be combined with the electrode of the present invention may consist only of the electrode active material, or they may be mixed with the above-mentioned binder, conductive material, solid electrolyte, etc.

[0043] The electrolyte layer used in secondary batteries can be broadly classified into two types: those composed primarily of an electrolyte solution and those composed of a solid electrolyte.

[0044] (1) Non-aqueous electrolyte layer The non-aqueous electrolyte layer used in the present invention can be composed of a mixture of an electrolyte and a non-aqueous solvent. Examples of electrolytes include LiClO4, LiPF6, LiBF4, LiCF3SO3, LiAsF6, LiB(C6H5)4, LiCl, LiBr, CH3SO3Li, CF3SO3Li, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiC(SO2CF3)3, or LiN(SO3CF3)2. The non-aqueous solvent is not particularly limited and includes, for example, carbonates, ethers, ketones, sulfolane compounds, lactones, nitriles, chlorinated hydrocarbons, amines, esters, amides, phosphate ester compounds, and the like. Representative examples of these include 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, ethylene carbonate, vinylene carbonate, methyl formate, dimethyl sulfoxide, propylene carbonate, acetonitrile, γ-butyrolactone, dimethylformamide, dimethyl carbonate, diethyl carbonate, sulfolane, ethyl methyl carbonate, 1,4-dioxane, 4-methyl-2-pentanone, 1,3-dioxolane, 4-methyl-1,3-dioxolane, diethyl ether, sulfolane, methylsulfolane, propionitrile, benzonitrile, butyronitrile, valeronitrile, 1,2-dichloroethane, trimethyl phosphate, triethyl phosphate, etc. These can be used individually or in combination of two or more.

[0045] (2) Solid electrolyte layer The solid electrolyte constituting the solid electrolyte layer is not particularly limited, and any solid electrolyte that can be used in an all-solid-state secondary battery can be used. The solid electrolyte can be composed of, for example, a sulfide-based solid electrolyte material or an oxide-based solid electrolyte material. Examples of sulfide-based solid electrolyte materials include Li2S-P2S5, Li2S-P2S5-LiI, Li2S-P2S5-LiI-LiBr, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-GeS2, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, Li2S-P2S5, Li 10 GeP2S 12 Li7P3S 11 Li3PS4, or Li 3.25 P 0.75Examples include S4. These sulfide-based solid electrolyte materials may be used alone or in combination of two or more kinds. Examples of oxide-based solid electrolyte materials include, for example, Li2O-B2O3-P2O3, Li2O-SiO2, Li2O-P2O5, Li5La3Ta2O 12 , Li7La3Zr2O 12 , Li6BaLa2Ta2O<{ 12 Li 3.6 SI 0.6 P 0.4 O4 or Li3BO3-Li2SO4-Li2CO3, etc. can be mentioned. Also, the solid electrolyte of the present invention can be used. These oxide-based solid electrolyte materials may be used alone or in combination of two or more kinds.

[0046] The solid electrolyte layer may contain, in addition to the above solid electrolyte materials, other components used in all-solid-state secondary batteries. For example, metal oxides such as P, As, Ti, Fe, Zn or Bi, the above binder, conductive materials, etc. can be mentioned.

[0047] The solid electrolyte can be made into a solid electrolyte layer, for example, by pressing to a predetermined thickness. The pressure for pressing may be selected from pressures in the range of 50 - 2000 MPa.

[0048] (Method for manufacturing a secondary battery) The present invention also provides a method for manufacturing a secondary battery using the electrode and electrode composite of the present invention. (I) Lithium ion secondary battery When manufacturing a lithium ion secondary battery, for example, a laminate of the positive electrode of the present invention, a separator, and a negative electrode for a lithium ion secondary battery is inserted into a battery can, and a mixture of an electrolyte and a non-aqueous solvent is poured into the battery can to obtain a lithium ion secondary battery. It is preferable to use a microporous polymer film as the separator. Specifically, separators made of polyolefin polymers such as nylon, cellulose acetate, nitrocellulose, polysulfone, polyacrylonitrile, polyvinylidene fluoride, polypropylene, polyethylene, or polybutene can be used. The positive electrode, separator, and negative electrode may be stacked or wound. The electrode composite of the present invention may be used instead of the positive and negative electrodes. (II) All-solid-state battery A solid-state battery can be obtained, for example, by stacking the positive electrode, solid electrolyte layer, negative electrode, and current collector of the present invention, pressing them together to obtain a cell, and then fixing this cell in a container. A metal layer selected from Au, Pt, In, Al, Sn, or Si may be provided between the electrode and the solid electrolyte layer. The thickness of the metal layer is preferably 10 nm to 100 μm. [Examples]

[0049] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited thereto. In the following examples and comparative examples, sulfur was supplied by Tsurumi Chemical Industries, Ltd., and carbon particles were supplied by Lion Specialty Chemicals Co., Ltd.'s ECP-600JD. A twin-screw fusion kneader, the Hot-Melt Kneader: HMK, ZE-9 from Three-Tec GmbH, was used. For mixing using a planetary ball mill, a planetary ball mill device, PULVERISETTE 7 (P-7) from Fritsch, was used. For constant current charge and discharge measurements, a charge and discharge analyzer (BTS-2004) from Nagano was used. A scanning electron microscope (SEM) from Hitachi High-Technologies Corporation, the SU-3500, was used, and for energy-dispersive X-ray analysis (EDX), an ELEMENT EDS from EDAX Corporation was used. For ionic conductivity measurements, a digital electrometer 8252 from ADC Corporation was used.

[0050] As shown below, several composite particle samples for electrodes and comparative examples were prepared, and their properties were investigated. (LPS manufacturing) In the following experiments, Li3PS4 (LPS) was used as the solid electrolyte. This section describes the method for producing LPS. LPS was synthesized using Li2S and P2S5 as raw materials by the liquid-phase vibration method. Li2S and P2S5 were weighed in a molar ratio of 3:1, and ethyl propionate (SIGMA-ALDRICH, 99%) was added at a ratio of 10 mL per 1 g of total Li2S and P2S5 to prepare a solution. Zirconia balls were added to this solution, and the mixture was shaken for 6 hours in a shaking mixer (CM-1000, EYELA) to obtain a solid electrolyte precursor. The supernatant was then removed, and the mixture was dried under reduced pressure for 1 hour (25°C, -0.1 MPa), followed by heat treatment for 2 hours (200°C) to synthesize LPS. The ionic conductivity of the synthesized Li3PS4 was 8.2 × 10⁻⁶. -5 The value was S / cm.

[0051] Example 1 (Preparation of composite particles for electrodes 1) Composite particles for electrodes were prepared by heating and kneading sulfur, carbon particles, and LPS in a twin-screw fusion kneader using the following procedure. Sulfur, carbon particles, and LPS were placed in a container in a mass ratio of sulfur:carbon particles:LPS = 50:10:40 and mixed by shaking in a vortex mixer for 5 minutes. This mixture was added to a twin-screw fusion kneader and processed at a processing temperature of 150°C, 30 rpm, and 1 pass to produce the electrode composite particles of Example 1.

[0052] Comparative Example 1 For comparison, a sample processed using a planetary ball mill instead of a twin-screw fusion kneader was prepared using the following procedure. Sulfur, carbon particles, and LPS were placed in a container in a mass ratio of sulfur:carbon particles:LPS = 50:10:40 and mixed by shaking in a vortex mixer for 5 minutes. 0.4 g of this mixture was added to a planetary ball mill and subjected to ball milling to prepare the sample for Comparative Example 1. The ball milling conditions were as follows: 40 g of 5 mm diameter zirconia balls were used and the process was carried out at a speed of 370 rpm for 120 minutes.

[0053] Comparative Example 2 The sample for Comparative Example 2 was prepared in the same manner as for Comparative Example 1, except that the ball milling time was set to 180 minutes.

[0054] Comparative Example 3 The sample for Comparative Example 3 was prepared in the same manner as for Comparative Example 1, except that the ball milling time was set to 240 minutes.

[0055] Comparative Example 4 The sample for Comparative Example 4 was prepared in the same manner as for Comparative Example 1, except that LPS was not added and sulfur and carbon particles were placed in a container in a mass ratio of sulfur:carbon particles = 50:10.

[0056] Example 2 (Fabrication of composite particles for electrodes 2) Composite particles for electrodes were prepared by heating and kneading sulfur and carbon particles in a twin-screw fusion kneader using the following procedure. Sulfur and carbon particles were placed in a container in a mass ratio of sulfur:carbon particles = 50:10, and mixed by shaking in a vortex mixer for 5 minutes. This mixture was added to a twin-screw fusion kneader and processed at a processing temperature of 150°C, 30 rpm, and 1 pass to produce the electrode composite particles of Example 2.

[0057] Example 3 (Preparation of composite particles for electrodes 3) The composite particles for the electrodes of Example 4 were prepared in the same manner as in Example 2, except that the processing temperature using a twin-screw fusion kneader was set to 170°C.

[0058] Example 4 (Preparation of composite particles for electrodes 4) The electrode composite particles of Example 4 were prepared in the same manner as in Example 2, except that the processing temperature using a twin-screw fusion kneader was set to 190°C.

[0059] Example 5 (Preparation of composite particles for electrodes 5) The composite particles for the electrodes of Example 5 were prepared in the same manner as in Example 2, except that the number of passes during processing with the twin-screw fusion kneader was reduced to two.

[0060] Example 6 (Preparation of composite particles for electrodes 6) The composite particles for the electrodes of Example 6 were prepared in the same manner as in Example 2, except that the number of passes during processing with the twin-screw fusion kneader was set to three.

[0061] Example 7 (Preparation of composite particles for electrodes 7) The electrode composite particles of Example 6 and LPS were added to a planetary ball mill in a mass ratio of electrode composite particles:LPS = 60:40, totaling 0.4g. Ball milling was then performed to produce the electrode composite particles of Example 7 containing LPS. The ball milling conditions were as follows: 40g of 5mm diameter zirconia balls were used and the process was carried out at a speed of 370rpm for 120 minutes.

[0062] Example 8 (Preparation of composite particles for electrodes 8) The composite particles for the electrode in Example 8 were prepared in the same manner as in Example 7, except that the ball milling time was set to 180 minutes.

[0063] Example 9 (Preparation of composite particles for electrodes 9) The composite particles for the electrodes of Example 9 were prepared in the same manner as in Example 7, except that the ball milling time was set to 240 minutes.

[0064] Example 10 (Preparation of composite particles for electrodes 10) The electrode composite particles of Example 10 were prepared in the same manner as in Example 2, except that the mixing ratio of sulfur to carbon particles was set to a mass ratio of sulfur:carbon particles = 75:25.

[0065] Example 11 (Preparation of composite particles for electrodes 11) The electrode composite particles of Example 11 were prepared in the same manner as in Example 2, except that the mixing ratio of sulfur and carbon particles was set to a mass ratio of sulfur:carbon particles = 50:50.

[0066] Comparative Example 5 For comparison, a sample for Comparative Example 5 was prepared by simply placing sulfur and carbon particles in a container in a mass ratio of sulfur:carbon particles = 50:10 and mixing them by shaking in a vortex mixer for 5 minutes.

[0067] Comparative Example 6 The sample for Comparative Example 6 was prepared in the same manner as for Comparative Example 5, except that the mixing ratio of sulfur to carbon particles was set to a mass ratio of sulfur:carbon particles = 75:25.

[0068] Comparative Example 7 The sample for Comparative Example 7 was prepared in the same manner as for Comparative Example 5, except that the mixing ratio of sulfur to carbon particles was set to a mass ratio of sulfur:carbon particles = 50:50.

[0069] The characteristics of Examples 1-11 and Comparative Examples 1-7 described above are summarized in Table 1 below.

[0070] [Table 1]

[0071] (Charge / discharge capacity measurement) Charge-discharge tests were conducted using the fabricated composite particles for electrodes and the samples. For the half-cell used in the test, a compression molded body with a diameter of 10 mm obtained by sandwiching a positive electrode layer, a solid electrolyte layer, and a negative electrode in a cylindrical container between a pair of current collectors made of SUS and applying pressure at 200 MPa for 1 minute was used. 7.5 mg of the prepared composite particles were used for the positive electrode layer, 80 mg of LPS was used for the electrolyte layer, and a lithium / indium alloy foil (molar ratio Li / In = 0.79) was used for the negative electrode. The battery performance of the fabricated half-cell was evaluated in a thermostatic bath at 25 °C using a battery charge-discharge test device (BTS2004, Nagano Co., Ltd.). The voltage range was set to 0.5 - 2.5 V (1.1 - 3.1 V based on Li / Li+). The first cycle was measured in a constant current (CC) charge mode with a current density of 0.25 mA / cm 2 (equivalent to 0.04 C). The second cycle was measured in a constant current (CC) charge mode with a current density of 0.38 mA / cm 2 (equivalent to 0.06 C). For the third cycle and subsequent cycles, the charge and discharge were both measured in a constant current (CC) charge mode with a current density of 0.64 mA / cm 2 (equivalent to 0.1 C).

[0072] The results of charge-discharge tests on the half-cells fabricated using the composite particles for electrodes of Example 1 and the samples of Comparative Example 1 are shown in Figure 2. From Figure 2, the initial discharge capacity of the composite particles for electrodes of Example 1 is 383 mAh / g-S, while that of the sample of Comparative Example 1 is 193 mAh / g-S. Thus, it was shown that the composite particles for electrodes of Example 1 fabricated using a biaxial melt-kneader have an initial discharge capacity superior to that of the sample of Comparative Example 1.

[0073] The results of charge-discharge tests on the half-cells fabricated using the composite particles for electrodes of Examples 2 - 6, 10, and 11 are shown in Figures 3A - C, respectively. Also, the charge-discharge capacities of these composite particles for electrodes are shown in Table 2 below. From Figures 3A - C and Table 2, it was shown that the composite particles for electrodes of Examples 2 - 6, 10, and 11 have charge-discharge capacities superior to those of the sample of Comparative Example 1.

[0074]

Table 2

[0075] (Observation of composite particles for electrodes) Figures 4A, 4B, 5A, and 5B show the results of observing the composite electrode particles of Examples 2-4 and the sample of Comparative Example 5 using a scanning electron microscope (SEM). Figure 4A shows the SEM image of the sample of Comparative Example 5, Figure 4B shows the SEM image of the composite electrode particles of Example 2, Figure 5A shows the SEM images of the composite electrode particles of Examples 2-4, and Figure 5B shows the SEM images of Examples 2, 5, and 6. For reference, the sulfur (D) used in the present invention is also shown. 50 =23.5μm), carbon particles (primary particle size 34nm) and LPS (D 50 Figures 6A and 6C show SEM images of particles (8.5 μm). Figure 6A shows sulfur, Figure 6B shows carbon particles, and Figure 6C shows LPS. From Figures 4A and 4B, it can be seen that in Figure 4A, many aggregates of nanometer-sized carbon particles are observed, whereas in Figure 4B, almost no aggregates of carbon particles are observed, and particles of about several tens of micrometers are observed. From Figures 5A and 5B, it can be seen that in all of the particles of Examples 2 to 6, particles with a particle diameter of several tens of micrometers to about 100 μm are observed. In addition, it can be seen that the surface of each particle is covered with carbon particles. From these findings, it is shown that by melt-kneading using a twin-screw fusion kneader, the molten sulfur incorporates carbon particles and becomes larger, and composite particles for electrodes in which carbon particles are dispersed on the surface and inside the sulfur can be produced.

[0076] (Measurement of particle size distribution) The particle size distribution of the composite electrode particles prepared in Examples 2-6 and the sample of Comparative Example 5 was measured. A Shimadzu SALD2100 was used for the particle size distribution measurement. Here, particle size refers to the volume-average particle diameter. The results of the particle size distribution of the composite electrode particles in Examples 2-6 and the sample of Comparative Example 5 are shown in Figures 7A and 7B, respectively. 10 , D 50 and D 90 The measurement results are shown in Table 3.

[0077] [Table 3]

[0078] Table 3, Figure 7A, and Figure 7B show that the particle size is larger when the mixture is melt-kneaded using a twin-screw fusion kneader compared to the sample that was not melt-kneaded.

[0079] Similar to the electrode composite particles of Examples 2-6, the particle size distribution was also measured for the electrode composite particles of Examples 10 and 11 and the samples of Comparative Examples 6 and 7. The results for Example 10 and Comparative Example 6 are shown in Figure 7C, and the results for Example 11 and Comparative Example 7 are shown in Figure 7D. 10 , D 50 and D 90 The measurement results are shown in Table 4.

[0080] [Table 4]

[0081] Table 4, Figure 7C, and Figure 7D show that the electrode composite particles of Example 10, which were melt-kneaded using a twin-screw fusion kneader, have a larger particle size compared to Comparative Example 6, which was simply a mixture of sulfur and carbon particles in the same proportion as in Example 10. Similarly, the electrode composite particles of Example 11 also show a larger particle size compared to the sample of Comparative Example 7. This indicates that melt-kneading using a twin-screw fusion kneader causes the molten sulfur particles to stick together while incorporating carbon particles, resulting in larger particle sizes.

[0082] (Nitrogen adsorption test) Nitrogen adsorption isotherms were prepared for the electrode composite particles of Examples 2-6, 10, and 11, and for the samples of Comparative Examples 5-7. The nitrogen adsorption isotherms were prepared as follows. The sample was dried under reduced pressure for 3 hours at 1 Pa and 50°C. The N2 adsorption isotherm (77 K) of the sample after reduced pressure drying was measured using a gas / vapor adsorption spectrometer (BELSOP-mini II, Microtrac-Bel).

[0083] The measured nitrogen adsorption isotherms are shown in Figures 8A to D. Figure 8A shows the measurement results for the electrode composite particles of Examples 2 to 4 and the sample of Comparative Example 5; Figure 8B shows the measurement results for the electrode composite particles of Examples 2, 5, and 6 and the sample of Comparative Example 5; Figure 8C shows the measurement results for the electrode composite particles of Example 6 and the samples of Comparative Examples 4 and 5; and Figure 8D shows the measurement results for the electrode composite particles of Examples 2, 10, and 11 and the samples of Comparative Examples 5 to 7. The BET specific surface area and total pore volume calculated based on these measurement results are shown in Table 5.

[0084] [Table 5]

[0085] Table 5 and Figures 8A and 8B show that the electrode composite particles of Examples 2-6, which were melt-kneaded using a twin-screw fusion mixer, have a lower BET specific surface area compared to Comparative Example 5, which was simply a mixture of sulfur and carbon particles in equal proportions. Table 5 and Figure 8C show that the electrode composite particles of Example 6, which were melt-kneaded using a twin-screw fusion mixer, also have a lower BET specific surface area compared to Comparative Example 5, which was simply a mixture of sulfur and carbon particles in equal proportions. Table 5 and Figure 8D show that the electrode composite particles of Example 10, which were melt-kneaded using a twin-screw fusion mixer, have a lower BET specific surface area compared to Comparative Example 6, which was simply a mixture of the same proportions. Similarly, the electrode composite particles of Example 11 also have a lower BET specific surface area compared to the sample of Comparative Example 7. In this experiment, the maximum nitrogen adsorption capacity of the carbon particles used individually was 1500 ml(STP) / g. Assuming that sulfur does not have pores, the maximum nitrogen adsorption capacity of the sulfur-carbon particle mixture in Example 2 was 250 ml(STP) / g (sulfur:carbon particles = 50:10), while the adsorption capacity of the electrode composite particles in Example 2 was 36.6 ml(STP) / g, indicating a decrease in adsorption capacity. From the above, it was shown that sulfur incorporated the carbon particles through melt kneading, and sulfur impregnated the pores of the carbon particles.

[0086] (XRD measurement) X-ray diffraction (XRD) measurements were performed on the electrode composite particles of Example 6 and the samples of Comparative Examples 1 and 5. A Rigaku SmartLab X-ray diffractometer was used, and the sample was packed with a constant volume so that the cell cavity was completely filled, and CuKα radiation (= 1.54056 × 10⁻¹⁶) was detected. -10 Using m), with a tube voltage of 45 kV, tube current of 200 mA, scanning angle 2θ = 10° to 60°, sampling interval of 0.02°, and scanning speed of 10°min, -1 Structural analysis was performed under the following conditions.

[0087] The results of the XRD measurements are shown in Figures 9A and 9B, respectively. From Figures 9A and 9B, it can be seen that while the samples of Comparative Examples 1 and 5 show strong peaks originating from sulfur, the composite particles for electrodes of Example 6 show smaller peaks. This is thought to be because the sulfur impregnated into the carbon particles became amorphous due to the melt-kneading process. This indicates that composite particles for electrodes containing amorphous sulfur inside the carbon particles can be obtained by performing a melt-kneading treatment.

[0088] (Measurement of angle of repose) The angles of repose were measured for the electrode composite particles of Example 6 and the sample of Comparative Example 5. The angles of repose here are static angles of repose, and were specifically measured as follows using a Seishin Corporation MT-1001k multi-tester. The measurement was performed by dropping the composite particles or sample to be measured onto a horizontal substrate from a funnel of a certain height, and measuring the angle at which the free surface formed by the deposited powder becomes horizontal.

[0089] The measurement results of the angle of repose are shown in Figures 10A and 10B. The angle of repose of the sample in Comparative Example 5 was 58.4°, while the angle of repose of the electrode composite particles in Example 6 was 44.1°. This indicates that the electrode composite particles manufactured by melt kneading have improved fluidity.

[0090] (SEM-EDX measurement) The electrode composite particles from Example 6 and the sample from Comparative Example 5 were subjected to SEM-EDX. Measurements were performed at an acceleration voltage of 8 kV. The measurement results for the electrode composite particles of Example 6 are shown in Figure 11A, and the results for the sample of Comparative Example 5 are shown in Figure 11B. In Figures 11A and 11B, C represents the mapping image of carbon, and S represents the mapping image of sulfur. From Figures 11A and 11B, it can be seen that the mapping of C and S does not match in the sample of Comparative Example 5, whereas the mapping of C and S matches in the electrode composite particles of Example 6. This indicates that the molten sulfur incorporated the carbon particles during melt kneading to form the particles.

[0091] (Effects due to changes in charge / discharge rate) Using the electrode composite particles from Examples 7-9 and the samples from Comparative Examples 1-3, half-cells were prepared, and the charge-discharge capacities were measured and compared by varying the charge-discharge rate. The charge-discharge capacities were measured in the same manner as described above.

[0092] Figure 12 shows the charge-discharge curves of half-cells prepared using the electrode composite particles of Example 7 and the sample of Comparative Example 1. From Figure 12, the initial discharge capacity of the half-cell prepared using the electrode composite particles of Example 7 was 871 mAh / gS, and the initial discharge capacity of the half-cell prepared using the sample of Comparative Example 1 was 185 mAh / gS. From this, it can be seen that the initial discharge capacity of the half-cell prepared using the electrode composite particles of Example 7 is approximately 4.7 times higher than that of the half-cell prepared using the sample of Comparative Example 1.

[0093] Figure 13 shows the results of varying the charge-discharge rate of half-cells prepared using the electrode composite particles of Example 7 and the sample of Comparative Example 1. From Figure 13, it can be seen that in the half-cell prepared using the sample of Comparative Example 1, the capacity decreased significantly when the charge-discharge rate was increased, and the charge-discharge capacity became almost 0 at 0.1C. In contrast, the half-cell prepared using the electrode composite particles of Example 7 had a high initial discharge capacity of 532 mAh / gS and an initial charge capacity of 193 mAh / gS at a charge-discharge rate of 0.1C.

[0094] Figure 14 shows the charge / discharge capacities for each charge / discharge cycle of half-cells fabricated using the electrode composite particles of Example 7 and the sample of Comparative Example 1. The C rate for each cycle was 0.04 C for the first cycle, 0.06 C for the second cycle, and 0.1 C for cycles 3-5. From Figure 14, it can be seen that the charge / discharge capacity of the half-cell fabricated using the sample of Comparative Example 1 became almost zero by the third cycle, whereas the charge / discharge capacity of the half-cell fabricated using the electrode composite particles of Example 7 was maintained even after five cycles. This indicates that the performance of the battery is improved by manufacturing an all-solid-state battery using electrode composite particles that have undergone melt-kneading treatment.

[0095] The charge-discharge capacities of half-cells prepared using the electrode composite particles of Examples 7-9 and the samples of Comparative Examples 1-3 were measured and compared. The results shown here represent the average value of two charge-discharge tests performed on each half-cell. The measurement results are shown in Figure 15 and Table 6. From Figure 15 and Table 6, it was shown that the half-cells of Examples 7-9, which used electrode composite particles that underwent melt-kneading treatment, had superior charge-discharge capacities compared to the half-cells of Comparative Examples 1-3, which used samples that underwent ball milling only, regardless of the ball milling time.

[0096] [Table 6]

[0097] (Impedance measurement) Impedance measurements were performed using half-cells prepared with the electrode composite particles of Examples 7-9 and the samples of Comparative Examples 1-3. The impedance measurements were performed according to the following procedure. Each half-cell was charged and discharged for one cycle and then discharged for two cycles in a constant temperature bath at 25°C using a Nagano charge / discharge measurement device. The voltage range at this time was 0.5-2.5 V (Li / Li + The reference voltage is 1.1-3.1 V, and the current density is 0.25 mA / cm² for both cycles 1 and 2. 2The circuit was set to a constant current (CC) charge / discharge mode (equivalent to 0.04 C). After two cycles of discharge, the charge transfer resistance of each half-cell was evaluated by measuring the AC impedance using a high-performance electrochemical measurement system (SP-200, Bio-Logic, Sciences Instruments). The applied voltage was 10 mV, and the frequency range was 7 MHz to 1 mHz.

[0098] The results of the impedance measurements are shown in Figure 16 and Table 7, respectively. From Figure 16 and Table 7, it can be seen that the resistance value did not change with or without the melt-kneading treatment.

[0099] [Table 7]

[0100] (Measurement of ionic conductivity) The ionic conductivity of the electrode composite particles of Example 9 and the sample of Comparative Example 3 was measured using an electron blocking cell. A schematic diagram of the electron blocking cell is shown in Figure 17. The electron blocking cell was manufactured as follows. 40 mg of the above LPS was added as a solid electrolyte to a polycarbonate tube with an inner diameter of 10.1 mm. The top was pressed down with a rod (made of SKD, diameter: 10.0 mm), and then pressed for 3 minutes at 75 MPa using a press machine (Riken Kiki Co., Ltd., MS05-100). After pressing, 80 mg of the electrode composite particles of Example 7 or the sample of Comparative Example 1 was added to the LPS pellet, the rod was placed on top, and the polycarbonate tube was rotated 8.5 times to the left and right to homogenize the sample. Then, it was pressed for 3 minutes at 75 MPa using the press machine. After pressing, another 40 mg of LPS was added to the pellet, the top of the rod was pressed down, and then it was pressed for 3 minutes at 200 MPa using the press machine. Li foil (diameter: 7 mm, thickness: 0.1 mm), whose surface was polished until glossy, was placed on both ends of this molded body. Furthermore, an electron blocking cell was fabricated by creating a layer of Li-In alloy (molar ratio Li / In = 0.79) by layering an In foil (diameter: 9 mm, thickness: 0.3 mm) with its surface polished until glossy onto a Li foil.

[0101] The ionic conductivity of the fabricated electron blocking cell was measured using the following procedure. After allowing the cell voltage to settle until it reached 0V, the DC resistance was evaluated by measuring it after 10 minutes using an ADC Corporation Digital Electrometer 8252 in DCV mode.

[0102] The results of the ionic conductivity measurements are shown in Table 8. From Table 8, it was shown that the electrode composite particles that underwent melt-kneading treatment showed improved ionic conductivity compared to the sample that had only undergone ball milling.

[0103] [Table 8]

[0104] From the above, it was found that by performing a melt-kneading treatment on sulfur and carbon particles, electrode composite particles in which carbon particles are dispersed within sulfur can be obtained. These electrode composite particles have excellent solid-to-solid contact interfaces and therefore possess superior properties as electrode materials compared to simply mixing sulfur and carbon particles or samples subjected to ball milling. Furthermore, since these electrode composite particles can be manufactured using a twin-screw melt-kneading apparatus, productivity is also excellent.

Claims

1. Composite particles for electrodes comprising a crystalline sulfur phase and carbon particles dispersed within the crystalline phase, The volume-based average particle diameter (D50) of the carbon particles is in the range of 1 to 999 nm. The carbon particles have amorphous sulfur on the surface and / or inside the carbon particles. The composite particles for electrodes have a volume-based average particle diameter (D50) in the range of 1 to 1000 μm. Composite particles for electrodes, wherein the carbon particles are porous carbon particles, and amorphous sulfur is contained within the pores of the carbon particles.

2. The electrode composite particle according to claim 1, wherein the composite particle further comprises solid electrolyte particles having a volume-based average particle diameter (D50) in the range of 0.01 to 50 μm.

3. The composite particle for electrodes according to claim 1 or 2, wherein the nitrogen adsorption amount of the composite particle is 50% or less of the nitrogen adsorption amount of the carbon particles contained in the composite particle.

4. Composite particles for electrodes according to any one of claims 1 to 3, wherein the maximum nitrogen adsorption capacity of the carbon particles is 1000 ml (STP) / g or more.

5. The electrode composite particle according to any one of claims 1 to 4, wherein the carbon particles are at least one selected from acetylene black, furnace black, natural graphite, or artificial graphite.

6. The electrode composite particle according to claim 2 or any one of claims 3 to 5 that directly or indirectly references claim 2, wherein the solid electrolyte is a sulfide-based solid electrolyte.

7. Li 3 PS 4 、The 2 SP 2 S 5 、The 2 SP 2 S 5 -LiI、Li 2 SP 2 S 5 -LiCl、Li 2 SP 2 S 5 -LiI-LiBr、Li 2 SP 2 S 5 -Li 2 O、Li 2 SP 2 S 5 -Li 2 O-LiI、Li 2 S-SiS 2 、The 2 S-SiS 2 -LiI、Li 2 S-SiS 2 -LiBr、Li 2 S-SiS 2 -LiCl、Li 2 S-SiS 2 -B 2 S 3 -LiI、Li 2 S-SiS 2 -P 2 S 5 -LiI、Li 2 SB 2 S 3 、The 2 SP 2 S 5 -Ges 2 、LiI-Li 2 SP 2 O 5 、LiI-Li 3 MONTH 4 -P 2 S 5 、The 10 GeP 2 S 12 、The 7 P 3 S 11 、The 3.25 P 0.75 S 4 or Li 7-x PS 6-x Y x Composite electrode particles according to claim 2 or any one of claims 3 to 6 that directly or indirectly reference claim 2, wherein at least one selected from (wherein x is between 0 and 1.8 and Y is a halogen).

8. The composite particle for electrodes according to any one of claims 1 to 7, wherein the mass ratio of the crystalline sulfur phase to the carbon particles is in the range of sulfur:carbon particles = 1.0:0.1 to 1.

0.

9. Composite electrode particles according to claim 2 or any one of claims 3 to 8 that directly or indirectly references claim 2, wherein the mass ratio of the sulfur and carbon particles to the solid electrolyte particles is in the range of sulfur + carbon particles:solid electrolyte = 1.0:0.1 to 1.

0.

10. The BET specific surface area of ​​the composite particles, determined by the nitrogen adsorption isotherm, is 200 m². 2 Composite particles for electrodes according to any one of claims 1 to 9, wherein the amount is less than or equal to / g.

11. The BET specific surface area of ​​the composite particles, determined by the nitrogen adsorption isotherm, is 10 m². 2 Composite particles for electrodes according to any one of claims 1 to 10, wherein the amount is less than or equal to / g.

12. The electrode composite particle according to any one of claims 1 to 11, wherein the particle diameter (D10) at which the cumulative frequency of the volume-based particle diameter distribution of the composite particle reaches 10% is in the range of 0.5 to 50 μm, the volume-based average particle diameter (D50) is in the range of 1 to 100 μm, and the particle diameter (D90) at which the cumulative frequency of the volume-based particle diameter distribution reaches 90% is in the range of 5 to 500 μm.

13. The composite particle for electrodes according to claim 12, wherein the particle diameter (D10) at which the cumulative frequency of the volume-based particle diameter distribution of the composite particle reaches 10% is in the range of 10 to 20 μm, the volume-based average particle diameter (D50) is in the range of 50 to 100 μm, and the particle diameter (D90) at which the cumulative frequency of the volume-based particle diameter distribution reaches 90% is in the range of 100 to 500 μm.

14. An electrode active material comprising electrode composite particles according to any one of claims 1 to 13.

15. An electrode comprising electrode composite particles according to any one of claims 1 to 13 or an electrode active material according to claim 14.

16. A secondary battery comprising the electrode described in claim 15.

17. The secondary battery according to claim 16, wherein the secondary battery is an all-solid-state secondary battery.

18. A method for producing electrode composite particles according to any one of claims 1 to 13, comprising the step of heating and kneading a sulfur composition and carbon particles in a twin-screw fusion kneader.

19. The method for producing electrode composite particles according to claim 18, wherein the temperature during the heating and kneading is in the range of 120°C to 200°C.

20. A method for producing electrode composite particles according to claim 2 or claim 18 or 19, which directly or indirectly references claim 2, further comprising the step of adding and mixing solid electrolyte particles after heating and kneading.

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