Coated active material particles and method for producing same, electrode mixture, and lithium-ion secondary battery

Abstract

The present invention relates to coated active material particles comprising active material particles and a glass solid electrolyte layer, wherein at least a portion of the surface of the active material particles is coated with the glass solid electrolyte layer, and the glass solid electrolyte layer is composed of glass that satisfies all of the following conditions (1) to (4). (1) The glass contains Li and P as elements constituting a cationic component, and contains S as an element constituting an anionic component. (2) The composition of the glass satisfies, in at%, 30-42% of Li and 5-16% of P. (3) The glass has a glass transition point of 110-300°C. (4) The glass has a lithium-ion conductivity of 2 mS / cm or more at 25°C.

Description

Coated active material particles and their manufacturing method, electrode composite material, and lithium-ion secondary battery

[0001] This invention relates to coated active material particles and a method for producing the same. It also relates to an electrode mixture containing the above-mentioned coated active material particles and a lithium-ion secondary battery.

[0002] Lithium-ion rechargeable batteries are widely used in portable electronic devices such as mobile phones and laptop computers, as well as in automobiles. Traditionally, lithium-ion rechargeable batteries have used liquid electrolytes, but concerns about leakage and fire necessitated larger cases for safety design. Improvements were also desired regarding short battery life and narrow operating temperature range.

[0003] In contrast, all-solid-state lithium-ion secondary batteries, which use a solid electrolyte as the electrolyte for lithium-ion secondary batteries, are attracting attention because they offer advantages such as improved safety, faster charging and discharging, and smaller case size.

[0004] In all-solid-state lithium secondary batteries, the active material and solid electrolyte must be homogeneously mixed for optimal battery performance. Furthermore, the solid electrolyte must thinly and uniformly coat the surface of the active material.

[0005] As a method for producing active materials coated with solid electrolytes as described above, Non-Patent Document 1 discloses a method in which sulfide solid electrolyte powder, synthesized by dry mechanical milling and pulverized by wet pulverization, and positive electrode active material powder are collided with each other by mechanical impact force in a dry impact blending device, thereby covering the surface of positive electrode active material particles with sulfide solid electrolyte particles. Furthermore, Patent Document 1 discloses a method for producing electrode composites containing electrode active materials and ion conductors by mechanochemical treatment of metal halides and monovalent metal salts. Furthermore, Patent Document 2 discloses a method for producing composite particles for lithium-ion batteries, in which first composite particles with a first sulfide attached to the surface of particles containing active material and a second sulfide are used as raw materials, and the first sulfide and second sulfide are reacted in a solvent that dissolves the second sulfide to produce thiolysicone, which constitutes the solid electrolyte portion of the composite particles. Furthermore, Non-Patent Document 2 discloses positive electrode active material LiNi１／３ Mn １／３ Co １／３ O ２ Li on (NMC) ７ P ２ S ８ A method for directly producing I(LPSI) electrolyte using a liquid process is disclosed.

[0006] Japanese Patent Publication No. 2007-149438 Japanese Patent Publication No. 2019-121499

[0007] Nakamura H, et al. Dry coating of active material particles with sulfide solid electrolytes for an all-solid-state lithium battery. Journal of Power Sources, Vol. 448, 2020, 227579Matsuda R, et al. Composite Cathode of NCM Particles and Li3PS4-LiI Electrolytes Prepared using the SEED Method for All-Solid-State Lithium Batteries. IOP Conf. Series: Materials Science and Engineering Vol. 429, 2018, 012033

[0008] In the coating active materials obtained by the above methods, the solid electrolyte is amorphous with insufficient conductivity. Therefore, in order to use them in lithium secondary batteries, it was necessary to heat-treat the coating active material to precipitate crystals in the electrolyte. However, there are concerns that such heat treatment may degrade the performance of the active material.

[0009] Therefore, it is conceivable to use glass that has high ionic conductivity even in an amorphous (non-crystalline) state without heat treatment as a solid electrolyte. In order to coat the active material with a solid electrolyte made of such glass, the method described in Non-Patent Document 1 can be considered. However, after diligent research by the present inventors, it was found that it is difficult to pulverize the above glass to submicron-level fine particles as disclosed in Non-Patent Document 1 by mechanical milling and wet pulverization methods.

[0010] Therefore, the present invention aims to provide coated active material particles and a method for producing the same that can be used in electrode mixtures or lithium-ion secondary batteries to achieve sufficient battery characteristics. The invention also aims to provide electrode mixtures and lithium-ion secondary batteries containing the above-mentioned coated active material particles.

[0011] As a result of diligent research, the inventors have discovered that coated active material particles can be obtained by dry grinding and mixing a raw material glass solid electrolyte of a specific composition, which has a specific average particle size and high ionic conductivity even in an amorphous state without heat treatment, with active material particles. These coated active material particles can be used in electrode composites or lithium-ion secondary batteries to achieve sufficient battery characteristics.

[0012] One aspect of the present invention relates to coated active material particles comprising active material particles and a glass solid electrolyte layer, wherein at least a portion of the surface of the active material particles is coated with the glass solid electrolyte layer, and the glass solid electrolyte layer is made of glass that satisfies all of the following conditions (1) to (4): (1) The glass contains Li and P as elements constituting the cationic component and S as an element constituting the anionic component. (2) The composition of the glass satisfies Li: 30 to 42% and P: 5 to 16% in atomic percent. (3) The glass transition temperature of the glass is 110 to 300°C. (4) The lithium ion conductivity of the glass at 25°C is 2 mS / cm or more.

[0013] Another aspect of the present invention relates to an electrode mixture containing the above-mentioned coated active material particles.

[0014] Another aspect of the present invention relates to a lithium-ion secondary battery containing the above-mentioned coated active material particles.

[0015] Another aspect of the present invention relates to a method for producing coated active material particles, comprising dry grinding and mixing a raw material mixture containing a raw material glass solid electrolyte and active material particles, wherein the coated active material particles comprise the active material particles and a glass solid electrolyte layer, at least a portion of the surface of the active material particles is coated with the glass solid electrolyte layer, the average particle size of the raw material glass solid electrolyte is 20 to 500 μm, and the raw material glass solid electrolyte is made of glass that satisfies all of the following conditions (1) to (4): (1) The glass contains Li and P as elements constituting the cationic component and S as an element constituting the anionic component. (2) The composition of the glass satisfies Li: 30 to 42% and P: 5 to 16% in atomic percent. (3) The glass transition temperature of the glass is 110 to 300°C. (4) The lithium ion conductivity of the glass at 25°C is 2 mS / cm or more.

[0016] According to the present invention, coated active material particles can be obtained that, when used in an electrode mixture or a lithium-ion secondary battery, can achieve sufficient battery characteristics. The above coated active material particles can achieve sufficient battery characteristics when used in an electrode mixture or a lithium-ion secondary battery.

[0017] Figure 1 is a flow chart showing the method for manufacturing the glass that constitutes the glass solid electrolyte layer of the coated active material particles according to this embodiment. Figure 2 is a flow chart showing the method for manufacturing the coated active material particles according to this embodiment. Figure 3 is an image of the surface of the particles taken with a scanning electron microscope (SEM) during the production of the coated active material particles of Example 1 of the Examples. Figures 3(a) to (d) are images taken 5 minutes, 30 minutes, 1 hour, and 3 hours after the start of dry grinding and mixing of the raw material mixture, respectively. Figure 4 is an image of the surface of the coated active material particles obtained in Example 1 of the Examples taken with scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDX). Figure 4(a) is an image obtained by SEM observation. Figures 4(b) to (f) are elemental mapping images of Co, S, P, O, and Ni respectively obtained by EDX. Figure 5 is a graph showing the charge-discharge curve of the first cycle of a constant current charge-discharge test for a lithium-ion secondary battery made using the coated active material particles obtained in Example 1 of the Examples. Figure 6 is a graph showing the relationship between the number of cycles in a constant current charge-discharge test and the discharge capacity for a lithium-ion secondary battery fabricated using the coated active material particles obtained in Example 1 of the Examples.

[0018] The present invention will be described in detail below, but the present invention is not limited to the following embodiments and can be modified and implemented as appropriate without departing from the spirit of the invention. Furthermore, the "~" indicating a numerical range is used to mean that the numbers written before and after it are included as the lower limit and upper limit.

[0019] The glass solid electrolyte layer constituting the coated active material particles according to this embodiment is made of glass that has high ionic conductivity even in an amorphous state. However, as described above, it was difficult to pulverize this glass to submicron-level fine particles. As a result of the inventors' investigations, it was found that coated active material particles in which the surface of the active material particles is uniformly coated with the glass solid electrolyte layer can be obtained by dry pulverizing and mixing a raw material glass solid electrolyte made of the above glass and having a predetermined particle size with active material particles. This is presumed to be because the above glass has high ductility and does not easily deform into fine particles when pulverized alone, but when mixed with active material particles, it has the property of being easily pressed onto the surface of the active material particles and forming a coating while dispersed. Because the coated active material particles according to this embodiment have high adhesion between the active material particles and the glass solid electrolyte layer, sufficient battery characteristics can be achieved when used in electrode composites or lithium-ion secondary batteries.

[0020] 《Coated Active Material Particles》 The coated active material particles according to this embodiment include active material particles and a glass solid electrolyte layer, wherein at least a portion of the surface of the active material particles is coated with the glass solid electrolyte layer. Furthermore, the glass solid electrolyte layer is made of glass that satisfies all of the following conditions (1) to (4). (1) The glass contains Li and P as elements constituting the cationic component and S as an element constituting the anionic component. (2) The composition of the glass satisfies Li: 30 to 42% and P: 5 to 16% in atomic percent. (3) The glass transition temperature of the glass is 110 to 300°C. (4) The lithium ion conductivity of the glass at 25°C is 2 mS / cm or more.

[0021] <Active Material Particles> The active material particles are the core of the coated active material particles according to this embodiment. The active material particles may be primary particles, secondary particles (i.e., aggregates of primary particles), or a mixture of primary and secondary particles. From the viewpoint of particle fluidity, it is preferable that the active material particles have a uniform particle size.

[0022] The active material particles may be positive electrode active material particles or negative electrode active material particles.

[0023] The positive electrode active material particles are not particularly limited as long as they can reversibly progress occlusion and release of lithium ions, and desorption and insertion (intercalation) of lithium ions, and known positive electrode active material particles can be used. Examples of the positive electrode active material particles include lithium cobaltate (LiCoO ２ ), lithium nickelate (LiNiO ２ ), lithium manganate (LiMnO ２ ), lithium nickel manganese oxide, Li(Ni ｘ Co ｙ Mn ｚ M ａ )O ２ (x+y+z+a=1, 0≤x≤1, 0≤y≤1, 0≤z≤1, 0≤a≤1, and M is at least one selected from Al, Mg, Nb, Ti, Cu, Zn, and Cr), a composite metal oxide represented by the formula, Li ａ M ｂ (PO ４ ) ｃ (1≤a≤4, 1≤b≤2, 1≤c≤3, and M is at least one selected from Fe, V, Co, Mn, Ni, and VO), and polyanion olivine-type positive electrodes represented by the formula.

[0024] The negative electrode active material particles are not particularly limited as long as they can reversibly progress occlusion and release of lithium ions, and desorption and insertion (intercalation) of lithium ions, and known negative electrode active material particles can be used. Examples of the negative electrode active material particles include carbon-based materials such as graphite, hard carbon, and soft carbon, metals that can form an alloy with lithium such as aluminum, silicon, and tin, elemental lithium metal, amorphous oxides such as silicon oxide and tin oxide, and lithium titanate (Li ４ Ti ５ O １２ ), and the like.

[0025] The shape of the active material particles is not particularly limited, and may be, for example, spherical, elliptical, flat, or fibrous.

[0026] The active material particles preferably have an average particle size of 1 to 50 μm. From the viewpoint of suppressing side reactions on the surface of the coated active material particles, the average particle size is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more. Furthermore, from the viewpoint of lithium diffusion within the active material particles, the average particle size is preferably 50 μm or less, more preferably 30 μm or less, and even more preferably 20 μm or less.

[0027] In this specification, the average particle size refers to the average particle size (D50) expressed as the median diameter obtained from the volume-based particle size distribution chart, which is measured using a Microtrac MT3300EXII laser diffraction particle size distribution analyzer. When the active material particles are secondary particles or a mixture of primary and secondary particles, the average particle size of the active material particles refers to the D50 measured for the entire secondary particles or mixture of primary and secondary particles. In the coated active material particles according to this embodiment, the average particle size of the active material particles can be measured, for example, by observing a cross-section obtained by the resin embedding method using SEM. Alternatively, if the active material particles used in the manufacture of the coated active material particles are available, these active material particles can be measured using the apparatus described above.

[0028] <Glass Solid Electrolyte Layer> The glass solid electrolyte layer, which will be described later, is made of glass and plays the role of forming ion conduction paths within the active material particles.

[0029] The glass solid electrolyte layer is preferably 20 to 1000 nm thick. From the viewpoint of density of electrode formation, the thickness is preferably 20 nm or more, more preferably 50 nm or more, and even more preferably 100 nm or more. Furthermore, from the viewpoint of ensuring electron conductivity, the thickness is preferably 1000 nm or less, more preferably 900 nm or less, and even more preferably 800 nm or less.

[0030] The above thickness can be measured, for example, by cleaving the coated active material particles under conditions of no air exposure, exposing the normal surface of the cleaved surface of the glass solid electrolyte layer using an ion milling apparatus, and then placing the obtained sample into a SEM using an air-free transfer vessel for SEM observation.

[0031] The ratio of the thickness (μm) of the glass solid electrolyte layer to the average particle size (μm) of the active material particles is preferably 0.02 to 0.4. From the viewpoint of electrolyte filling efficiency in the positive or negative electrode, the ratio is preferably 0.02 or higher, more preferably 0.03 or higher, even more preferably 0.04 or higher, and even more preferably 0.05 or higher. Furthermore, from the viewpoint of electron conductivity, the ratio is preferably 0.4 or lower, more preferably 0.35 or lower, even more preferably 0.3 or lower, and even more preferably 0.25 or lower.

[0032] In the coated active material particles according to this embodiment, the ratio of the volume of the glass solid electrolyte layer to the total volume of the active material particles and the glass solid electrolyte layer is preferably 6 to 35 volume%. From the viewpoint of sufficiently coating the surface of the active material particles with the glass solid electrolyte layer, the ratio is preferably 6 volume% or more, more preferably 9 volume% or more, and even more preferably 12 volume% or more. Furthermore, from the viewpoint of maintaining the charge and discharge capacity of the lithium-ion secondary battery using the coated active material particles, the ratio is preferably 35 volume% or less, more preferably 30 volume% or less, and even more preferably 25 volume% or less.

[0033] The volume of active material particles and the volume of the glass solid electrolyte layer can be measured by binarizing images obtained from SEM observations in an environment not exposed to air.

[0034] In the coated active material particles according to this embodiment, the ratio of the mass of the glass solid electrolyte layer to the total mass of the active material particles and the glass solid electrolyte layer is preferably 5 to 30% by mass. From the viewpoint of sufficiently coating the surface of the active material particles with the glass solid electrolyte layer and more favorably realizing sufficient battery characteristics, the above ratio is preferably 5% by mass or more, more preferably 7% by mass or more, even more preferably 9% by mass or more, even more preferably 10% by mass or more, and particularly preferably 12% by mass or more. Furthermore, from the viewpoint of maintaining the charge and discharge capacity of the lithium-ion secondary battery using coated active material particles, the above ratio is preferably 30% by mass or less, more preferably 27% by mass or less, and even more preferably 25% by mass or less.

[0035] In the coated active material particles according to this embodiment, at least a portion of the surface of the active material particles is coated with a glass solid electrolyte layer. The coating rate of the surface of the active material particles by the glass solid electrolyte layer is preferably 50% or more. From the viewpoint of sufficiently coating the surface of the active material particles with the glass solid electrolyte layer and allowing the active material particles to contribute to the charge-discharge reaction, the above coating rate is preferably 50% or more, more preferably 60% or more, and even more preferably 70% or more. The higher the above coating rate, the better, with an upper limit of 100%. In other words, it is most preferable that the surface of the active material particles is completely coated with the glass solid electrolyte layer.

[0036] <Glass> Next, the glass that constitutes the glass solid electrolyte layer (hereinafter also referred to as "this glass") will be described. This glass contains Li and P as elements constituting the cation component, and S as an element constituting the anion component. Furthermore, the composition of this glass satisfies the requirements of Li: 30-42% and P: 5-16% in atomic percent.

[0037] When a conventional mechanical milling method is applied to a glass raw material mixture prepared by mixing the raw materials to satisfy the above composition, the resulting solid is an amorphous phase but does not have a glass transition temperature. However, as will be described later, this glass can be obtained by melting the glass raw material mixture and rapidly cooling it.

[0038] By producing glass as described above, high homogeneity can be achieved without residues such as residual sulfur or unreacted raw materials, resulting in high water resistance with suppressed hydrogen sulfide generation. Furthermore, unlike the mechanical milling method, it is not necessary to consider the hardness of the raw materials, and various anionic and cationic components can be selected to obtain the desired glass. As a result, high lithium ion conductivity can also be achieved.

[0039] This glass contains Li and P as elements constituting the cationic component, but may further contain at least one element selected from the group consisting of Sn, Sb, Si, Ge, Ga, Al, B, C, Mg, Ca, Sr, and Ba. In particular, from the viewpoint of water resistance, it is preferable to contain at least one element selected from the group consisting of Sb, Si, and Sn, and more preferably to contain Si. Furthermore, from the viewpoint of ionic conductivity, it is preferable to contain at least one of the elements Al and B.

[0040] This section explains each element that makes up the cationic component. Note that the content of each element in this glass is expressed as atomic percent relative to the total content of all elements in the glass.

[0041] Li is an essential element responsible for ion conduction as a solid electrolyte. The Li content in this glass is 30-42%, preferably 33-41%. From the viewpoint of lithium ion conductivity, the above content is 30% or more, preferably 33% or more, and more preferably 35% or more. From the viewpoint of vitrification, the above content is 42% or less, preferably 41% or less, and more preferably 40% or less.

[0042] P is an essential element for forming the glass phase. The P-S bond is highly resistant to both oxidation and reduction in sulfides. Therefore, it has a wide potential window as a solid electrolyte and excellent electrochemical stability. The P content in this glass is 5 to 16%, preferably 6 to 14%. From the viewpoint of vitrification, the above content is 5% or more, preferably 6% or more, and more preferably 7% or more. Also, from the viewpoint of lithium ion conductivity, the above content is 16% or less, preferably 14% or less, and more preferably 12% or less.

[0043] When this glass contains Si as an element constituting the cationic component, Si has the effect of increasing the viscosity of the melt and promoting vitrification. The Si content in this glass is preferably 0 to 10%, more preferably 0.5 to 10%, and even more preferably 2 to 9%. Here, from the viewpoint of suitably obtaining the effect of Si, the Si content when present is preferably 0.5% or more, and more preferably 2% or more. Furthermore, from the viewpoint of electrochemical stability, the Si content is preferably 10% or less, and more preferably 9% or less.

[0044] When this glass contains Sn as an element constituting the cationic component, Sn has the effect of increasing the viscosity of the melt and promoting vitrification. The Sn content in this glass is preferably 0 to 10%, more preferably 0.1 to 10%, and even more preferably 0.5 to 8%. Here, from the viewpoint of suitably obtaining the effect of Sn, the Sn content when present is preferably 0.1% or more, and more preferably 0.5% or more. Furthermore, from the viewpoint of electrochemical stability, the Sn content is preferably 10% or less, and more preferably 8% or less.

[0045] When this glass contains Sb as an element constituting the cation component, Sb has the effect of increasing the viscosity of the melt and promoting vitrification. The Sb content in this glass is preferably 0 to 10%, more preferably 0.1 to 8%, and even more preferably 1 to 5%. Here, from the viewpoint of suitably obtaining the effect of Sb, the Sb content when present is preferably 0.1% or more, and more preferably 1% or more. Furthermore, from the viewpoint of lithium ion conductivity, the Sb content is preferably 10% or less, more preferably 8% or less, and even more preferably 5% or less.

[0046] When this glass contains Ge as an element constituting the cation component, Ge has the effect of promoting improved lithium ion conductivity. The Ge content in this glass is preferably 0 to 10%, more preferably 0.1 to 8%, and even more preferably 1 to 5%. Here, from the viewpoint of suitably obtaining the effect of Ge, the Ge content when present is preferably 0.1% or more, and more preferably 1% or more. Furthermore, from the viewpoint of glass formation, the Ge content is preferably 10% or less, more preferably 8% or less, and even more preferably 5% or less.

[0047] When this glass contains Ga as an element constituting the cation component, Ga has the effect of promoting improved lithium ion conductivity. The Ga content in this glass is preferably 0 to 10%, more preferably 0.1 to 8%, and even more preferably 1 to 5%. Here, from the viewpoint of suitably obtaining the effect of Ga, the Ga content when Ga is included is preferably 0.1% or more, and more preferably 1% or more. Furthermore, from the viewpoint of glass formation, the Ga content is preferably 10% or less, more preferably 8% or less, and even more preferably 5% or less.

[0048] When this glass contains Al as an element constituting the cation component, Al has the effect of increasing the viscosity of the melt and promoting vitrification. The Al content in this glass is preferably 0 to 10%, more preferably 0.1 to 8%, and even more preferably 1 to 5%. Here, from the viewpoint of suitably obtaining the effect of Al, the Al content when included is preferably 0.1% or more, and more preferably 1% or more. Furthermore, from the viewpoint of lithium ion conductivity, the Al content is preferably 10% or less, more preferably 8% or less, and even more preferably 5% or less.

[0049] When this glass contains B as an element constituting the cation component, B has the effect of increasing the viscosity of the melt and promoting vitrification. The B content in this glass is preferably 0 to 10%, more preferably 0.1 to 8%, and even more preferably 1 to 5%. Here, from the viewpoint of suitably obtaining the effect of B, the B content when B is included is preferably 0.1% or more, and more preferably 1% or more. Furthermore, from the viewpoint of lithium ion conductivity, the B content is preferably 10% or less, more preferably 8% or less, and even more preferably 5% or less.

[0050] When this glass contains carbon (C) as an element constituting the cationic component, C has the effect of increasing the glass-forming ability. The C content in this glass is preferably 0 to 10%, more preferably 0.1 to 8%, and even more preferably 1 to 5%. Here, from the viewpoint of suitably obtaining the effect of C, the C content when C is present is preferably 0.1% or more, and more preferably 1% or more. Furthermore, from the viewpoint of lithium ion conductivity, the C content is preferably 10% or less, more preferably 8% or less, and even more preferably 5% or less.

[0051] When this glass contains alkaline earth metal elements as elements constituting the cation component, the alkaline earth metal elements have the effect of increasing the glass-forming ability. Examples of alkaline earth metal elements include one or more selected from the group consisting of Mg, Ca, Sr, and Ba. The content of each alkaline earth metal element in this glass is preferably 0 to 10%, more preferably 0.1 to 8%, and even more preferably 1 to 5%. Here, from the viewpoint of suitably obtaining the effect of alkaline earth metal elements, the content of each alkaline earth metal element when it is included is preferably 0.1% or more, and more preferably 1% or more. Also, from the viewpoint of lithium ion conductivity, the content of each alkaline earth metal element is preferably 10% or less, more preferably 8% or less, and even more preferably 5% or less. Furthermore, the total content of alkaline earth metal elements in this glass is preferably 0 to 20%, more preferably 0.2 to 18%, and even more preferably 1 to 15%. Here, the total content of the above is preferably 0.2% or more, more preferably 1% or more, preferably 20% or less, more preferably 18% or less, and even more preferably 15% or less.

[0052] This glass contains sulfur (S) as an element constituting the anionic component, but may further contain at least one element selected from the group consisting of F, Cl, Br, I, O, Se, N, and C. In particular, from the viewpoint of improving ionic conductivity, it is preferable to contain at least one element selected from the group consisting of F, Cl, Br, and I, more preferably at least one element selected from the group consisting of Cl, Br, and I, and even more preferably I. Furthermore, from the viewpoint of improving vitrification ability, it is preferable to contain at least one element selected from the group consisting of O, Se, N, and C.

[0053] This section explains each element that makes up the anionic component. Note that the content of each element in this glass is expressed as atomic percent relative to the total content of all elements in the glass.

[0054] S is an element that forms a P-S bond with P and is an essential element for forming the glass phase. The S content in this glass is preferably 30-60%, more preferably 33-55%, and even more preferably 37-50%. From the viewpoint of vitrification, the above content is preferably 30% or more, more preferably 33% or more, and even more preferably 37% or more. Also, from the viewpoint of lithium ion conductivity, the above content is preferably 60% or less, more preferably 55% or less, and even more preferably 50% or less.

[0055] When this glass contains a halogen element (X) as an element constituting the anionic component, X is an element that contributes to high lithium ion conductivity. The total content of X in this glass is preferably 0 to 20%, more preferably 1 to 20%, and may also be 1 to 12% or 2 to 10%. Here, from the viewpoint of suitably obtaining the effect of X, the total content when X is included is preferably 1% or more, more preferably 2% or more, even more preferably 3% or more, and particularly preferably 6% or more. Furthermore, from the viewpoint of preventing the precipitation of lithium halide crystals, the total content of X is preferably 20% or less, more preferably 19% or less, and even more preferably 17% or less. Also, the total content of X may be 12% or less, or 10% or less.

[0056] In particular, it is preferable that the combined content of Br and I accounts for 50% or more of the total content of X, more preferably 70% or more, and it is also possible that it accounts for 100%, i.e., X consists only of Br and I. Furthermore, the content ratio expressed as Cl:Br is preferably 100:0 to 0:100, more preferably 80:20 to 0:100, and even more preferably 60:40 to 0:100. However, this does not preclude X from containing only Cl.

[0057] If the glass contains F as an element constituting the anionic component, the F content in the glass is preferably 0.1 to 20%, may also be 0.1 to 10%, or 0.5 to 5%. Here, the F content is preferably 0.1% or more, more preferably 0.5% or more, even more preferably 3% or more, and particularly preferably 6% or more. Furthermore, the F content is preferably 20% or less, more preferably 19% or less, and even more preferably 17% or less. If lithium fluoride crystals are likely to precipitate, the F content may be 10% or less, or 5% or less.

[0058] When the glass contains Cl as an element constituting the anionic component, the Cl content in the glass is preferably 0.1 to 20%, may be 0.1 to 10%, or 0.5 to 5%. Here, the Cl content is preferably 0.1% or more, more preferably 0.5% or more, even more preferably 3% or more, and particularly preferably 6% or more. Furthermore, the Cl content is preferably 20% or less, more preferably 19% or less, and even more preferably 17% or less. If lithium chloride crystals are likely to precipitate, the Cl content may be 10% or less, or 5% or less.

[0059] When the glass contains Br as an element constituting the anionic component, the Br content in the glass is preferably 0.1 to 20%, may be 0.1 to 10%, or 1 to 8%. Here, the Br content is preferably 0.1% or more, more preferably 1% or more, even more preferably 3% or more, and particularly preferably 6% or more. Furthermore, the Br content is preferably 20% or less, more preferably 19% or less, and even more preferably 17% or less. If lithium bromide crystals are likely to precipitate, the Br content may be 10% or less, or 8% or less.

[0060] When this glass contains ion (I) as an element constituting the anionic component, I is particularly preferred because it contributes to improving ionic conductivity. The I content in this glass is preferably 0.1 to 20%, may also be 0.1 to 10%, 1 to 8%, or 2 to 6%. Here, the I content is preferably 0.1% or more, more preferably 1% or more, even more preferably 2% or more, even more preferably 3% or more, and particularly preferably 6% or more. Furthermore, the I content is preferably 20% or less, more preferably 19% or less, and even more preferably 17% or less. From the viewpoint of easily precipitating lithium iodide crystals or improving vitrification, the I content may be 10% or less, 8% or less, or 6% or less.

[0061] When this glass contains oxygen (O) as an element constituting the anionic component, O has the effect of improving ionic conductivity. The O content in this glass is preferably 0 to 5%, more preferably 0.1 to 4%, and even more preferably 0.5 to 3%. Here, from the viewpoint of suitably obtaining the effect of O, the O content when present is preferably 0.1% or more, and more preferably 0.5% or more. Furthermore, from the viewpoint of water resistance, the O content is preferably 5% or less, more preferably 4% or less, and even more preferably 3% or less.

[0062] When this glass contains Se as an element constituting the anionic component, Se has the effect of improving ionic conductivity. The Se content in this glass is preferably 0 to 5%, more preferably 0.1 to 4%, and even more preferably 0.5 to 3%. Here, from the viewpoint of suitably obtaining the effect of Se, the Se content when Se is included is preferably 0.1% or more, and more preferably 0.5% or more. Furthermore, from the viewpoint of water resistance, the Se content is preferably 5% or less, more preferably 4% or less, and even more preferably 3% or less.

[0063] When this glass contains nitrogen (N) as an element constituting the anionic component, N has the effect of improving ionic conductivity. The N content in this glass is preferably 0 to 5%, more preferably 0.1 to 4%, and even more preferably 0.5 to 3%. Here, from the viewpoint of suitably obtaining the effect of N, the N content when present is preferably 0.1% or more, and more preferably 0.5% or more. Furthermore, from the viewpoint of water resistance, the N content is preferably 5% or less, more preferably 4% or less, and even more preferably 3% or less.

[0064] When this glass contains carbon (C) as an element constituting the anionic component, C has the effect of improving ionic conductivity. The C content in this glass is preferably 0 to 5%, more preferably 0.1 to 4%, and even more preferably 0.5 to 3%. Here, from the viewpoint of suitably obtaining the effect of C, the C content when C is present is preferably 0.1% or more, and more preferably 0.5% or more. Also, from the viewpoint of water resistance, the C content is preferably 5% or less, more preferably 4% or less, and even more preferably 3% or less. Note that C may be an element constituting the cationic component or an anionic component. Whether C is included as an element in the above sense can be determined by measuring the glass by XPS (X-ray photoelectron spectroscopy), and C is not present in both states simultaneously.

[0065] This glass may contain other elements in addition to the elements constituting the cationic or anionic components, to the extent that it does not impair the effects of the present invention. Examples of other elements include Na, K, Y, Zr, Cr, Zn, Fe, Co, Ti, Mn, and the like.

[0066] The total content of the above-mentioned other elements in this glass may be expressed in atomic percent as, for example, 0 to 5%, or if other elements are included, 0.1 to 4%, or 0.5 to 3%. Here, the total content may be 0.1% or more, 0.5% or more, 5% or less, 4% or less, or 3% or less.

[0067] The composition of this glass should satisfy Li: 30-42% and P: 5-16% in atomic percent, but it is preferable that it also satisfies one or more of the following: S: 30-60%, X: 1-20%, Si: 1-10%, and Sn: 0.1-10%, preferably two or more, and more preferably three or more. Furthermore, if X: 1-20% is satisfied, it is more preferable that at least one of Br: 0.1-19% and I: 0.1-19% is satisfied. The composition of this glass may also satisfy one or more of the following: S: 30-60%, X: 1-12%, Si: 1-10%, and Sn: 0.1-10%, preferably two or more, and may also satisfy three or more. Furthermore, if X: 1-12% is satisfied, at least one of Br: 0.1-10% and I: 0.1-10% may also be satisfied.

[0068] The method for determining the constituent elements of this glass and their respective content (composition ratio) varies depending on the element. For example, P, S, Sn, Sb, Si, Ge, Ga, Al, Mg, Ca, Sr, Ba, and Se are determined by ICP emission spectrometry, Li and B by atomic absorption spectrometry, X by ion chromatography, and C, O, and N by XPS (X-ray photoelectron spectroscopy). Details of each analysis will be described in the Examples section below.

[0069] Furthermore, it can be confirmed that the glass solid electrolyte layer of the coated active material particles according to this embodiment is made of the glass that satisfies conditions (1) and (2) by analyzing the composition of the glass solid electrolyte layer as described above. In addition, it can be confirmed that the glass solid electrolyte layer is made of the glass that satisfies conditions (3) and (4) by actually fabricating and measuring glass with a composition that satisfies conditions (1) and (2).

[0070] The glass transition temperature of this glass is 110 to 300°C, preferably 130 to 300°C, more preferably 140 to 290°C, and particularly preferably 150 to 280°C. By melting a glass raw material mixture and rapidly cooling it, a glass having a glass transition temperature can be obtained. From the viewpoint of improving the stability of this glass, the glass transition temperature is 110°C or higher, preferably 130°C or higher, more preferably 140°C or higher, and particularly preferably 150°C or higher. Furthermore, from the viewpoint of moldability, the glass transition temperature is 300°C or lower, preferably 290°C or lower, and more preferably 280°C or lower. In this specification, the glass transition temperature is the temperature at the first inflection point of the DSC chart obtained by differential scanning calorimetry (DSC), and can be adjusted by the composition of the glass and the cooling rate from the melt.

[0071] The crystallization temperature of this glass is not particularly limited, but is preferably 130 to 400°C, more preferably 140 to 400°C, and particularly preferably 150 to 370°C. From the viewpoint of moldability, the crystallization temperature is preferably 130°C or higher, more preferably 140°C or higher, and particularly preferably 150°C or higher. Furthermore, from the viewpoint of the stability of this glass, the crystallization temperature is preferably 400°C or lower, and more preferably 370°C or lower.

[0072] In this specification, the crystallization temperature refers to the temperature at the peak of the exothermic peak observed when glass is subjected to DSC and heated at a heating rate of 10°C / min.

[0073] When the glass transition temperature of this glass is Tg and the crystallization temperature is Tc, the temperature difference expressed as (Tc - Tg) is preferably 10 to 200°C, and more preferably 20 to 180°C. Here, from the viewpoint of the stability of this glass, the above difference is preferably 10°C or more, and more preferably 20°C or more. Furthermore, from the viewpoint of productivity, the above difference is preferably 200°C or less, and more preferably 180°C or less.

[0074] When this glass is compacted into a powder at 380 MPa, its lithium-ion conductivity at 25°C is 2 mS / cm or more, preferably 3 mS / cm or more, and higher is preferable. In this specification, lithium-ion conductivity is determined by AC impedance measurement using a powder sample compacted at 380 MPa as the measurement sample. Specifically, the AC impedance measurement of the measurement sample is performed with a measurement frequency of 100 Hz to 1 MHz, a measurement voltage of 100 mV, and a measurement temperature of 25°C, and the value obtained from the resulting Nyquist plot is defined as the lithium-ion conductivity.

[0075] The lithium-ion conductivity described above can be adjusted by the composition of the glass, reducing thermal unevenness during rapid cooling of the molten glass raw material mixture, and controlling the cooling rate. In particular, this glass is obtained by melting and rapidly cooling the glass raw material mixture, rather than by the conventional mechanical milling method. This expands the region that can be vitrified, making it easier to include multiple desired anionic and cationic components, and as a result, it becomes possible to adopt a composition that achieves high lithium-ion conductivity.

[0076] The H2O2 of this glass after exposure to air with a dew point of -30°C for 1 hour. ２ The amount of hydrogen sulfide (S) generated is preferably 10 mL / g or less, more preferably 4 mL / g or less, even more preferably 1 mL / g or less, particularly preferably 0.1 mL / g or less, and the less the better. ２ The amount of S generated is an indicator of the water resistance of the glass. Note that the above H ２ The more specific measurement conditions for the amount of sulfur (H) generated are as follows: First, the sample is passed through a 100 μm mesh to obtain a powder with an average particle size of 10 to 20 μm. Then, 10 mg of this powder is exposed to air humidified to a dew point of -30°C for 1 hour, and the amount of hydrogen sulfide (H) measured is measured. ２ S) Monitor the amount generated and the total amount H ２ This is the amount of S produced.

[0077] It is preferable that the glass is amorphous, that is, does not contain a crystalline phase. The amorphous nature of the glass can be confirmed by the absence of diffraction peaks indicating crystals in the XRD pattern obtained by powder X-ray diffraction (XRD). If the glass is amorphous, the coated active material particles according to this embodiment can be obtained without performing heat treatment, which may degrade the performance of the active material particles and cause crystals to precipitate in the glass. In the coated active material particles according to this embodiment, the amorphous nature of the glass constituting the glass solid electrolyte layer can be confirmed, for example, by the following method: The active material particles used in the production of the coated active material particles and the coated active material particles are each measured by XRD. If, compared with the XRD pattern of the active material particles, no additional peaks are found in the XRD pattern of the coated active material particles, it can be said that the glass constituting the glass solid electrolyte layer does not contain a crystalline phase and is amorphous.

[0078] <Other Components> In addition to the above-mentioned active material particles and the glass solid electrolyte layer, the coated active material particles according to this embodiment may also contain other components. Examples of other components include conductive additives and binders.

[0079] Conventional conductive additives can be used, such as carbon-based materials like graphite, carbon black, and acetylene black, as well as metals like copper, nickel, stainless steel, and iron, and conductive oxides like indium tin oxide (ITO). Among these, carbon black and acetylene black are preferred from the viewpoint of reactivity.

[0080] If the coated active material particles according to this embodiment contain a conductive additive, the content is preferably greater than 0% by mass and 5% by mass or less. From the viewpoint of electron conductivity, the content is preferably greater than 0% by mass, more preferably 0.1% by mass or more, even more preferably 0.3% by mass or more, and even more preferably 0.5% by mass or more. Also, from the viewpoint of energy density, the content is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 2% by mass or less.

[0081] Conventional, publicly known binders can be used.

[0082] In the coated active material particles according to this embodiment, if the above-mentioned other components are included, the content of the active material particles in the whole, including the other components, is preferably 70 to 95% by mass. From the viewpoint of maintaining the charge and discharge capacity of the lithium-ion secondary battery using coated active material particles, the content is preferably 70% by mass or more, more preferably 73% by mass or more, and even more preferably 76% by mass or more. Furthermore, from the viewpoint of sufficiently coating the surface of the active material particles with the glass solid electrolyte layer and more favorably realizing sufficient battery characteristics, the content is preferably 95% by mass or less, more preferably 92% by mass or less, even more preferably 90% by mass or less, and particularly preferably 88% by mass or less.

[0083] In the coated active material particles according to this embodiment, if the above-mentioned other components are included, the content of the glass solid electrolyte layer in the whole, including the other components, is preferably 5 to 30% by mass. From the viewpoint of sufficiently coating the surface of the active material particles with the glass solid electrolyte layer and more favorably realizing sufficient battery characteristics, the content is preferably 5% by mass or more, more preferably 7% by mass or more, even more preferably 10% by mass or more, and particularly preferably 12% by mass or more. Furthermore, from the viewpoint of maintaining the charge and discharge capacity of the lithium-ion secondary battery using coated active material particles, the content is preferably 30% by mass or less, more preferably 27% by mass or less, and even more preferably 25% by mass or less.

[0084] The coated active material particles according to this embodiment preferably have an average particle size of 1 to 50 μm. From the viewpoint of suppressing side reactions on the surface of the coated active material particles, the average particle size is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more. Furthermore, from the viewpoint of lithium diffusion within the active material, the average particle size is preferably 50 μm or less, more preferably 30 μm or less, and even more preferably 20 μm or less.

[0085] Electrode mixture: The coated active material particles according to this embodiment may be used as an electrode mixture for the positive electrode layer or the negative electrode layer, as described later. That is, the electrode mixture according to this embodiment includes the coated active material particles.

[0086] Lithium-ion secondary battery The coated active material particles according to this embodiment may be used in a lithium-ion secondary battery. That is, the lithium-ion secondary battery according to this embodiment includes the coated active material particles. The lithium-ion secondary battery according to this embodiment includes a solid electrolyte layer, a positive electrode layer, and a negative electrode layer. The coated active material particles may be included in at least one of the positive electrode layer and the negative electrode layer, or in both.

[0087] Aside from the coated active material particles mentioned above, the configurations of the solid electrolyte layer, positive electrode layer, and negative electrode layer can be those of conventionally known standards. Specific examples of each configuration are shown below, but the invention is not limited to these.

[0088] <Positive Electrode Layer> The positive electrode layer contains at least a positive electrode current collector and a positive electrode composite material. The positive electrode composite material includes a positive electrode active material or a coated positive electrode active material and a solid electrolyte. The coated positive electrode active material may be coated active material particles according to this embodiment. Examples of the solid electrolyte include oxide-based solid electrolytes and sulfide-based solid electrolytes. The same applies to the solid electrolyte used in the negative electrode layer and solid electrolyte layer, which will be described later.

[0089] The positive electrode current collector can be any conductive plate material; for example, thin metal sheets (metal foils) such as aluminum or its alloys, or stainless steel can be used. These are preferable because they have excellent electrolyte resistance and oxidation resistance.

[0090] The positive electrode layer may further contain, for example, a conductive material. The conductive material can form electron conduction paths within the positive electrode layer. The amount of conductive material may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of positive electrode active material or coated positive electrode active material. The conductive material may contain any component. For example, the conductive material may contain at least one selected from the group consisting of acetylene black (AB), carbon black, vapor-grown carbon fiber (VGCF), carbon nanotubes (CNT), and graphene flakes.

[0091] The positive electrode layer may further contain, for example, a binder. The amount of binder may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of positive electrode active material or coated positive electrode active material. The binder may contain any components. For example, the binder may contain at least one selected from the group consisting of polyvinylidene fluoride (PVdF), vinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), styrene-butadiene rubber (SBR), and polytetrafluoroethylene (PTFE).

[0092] <Negative Electrode Layer> The negative electrode layer contains at least a negative electrode current collector and a negative electrode composite material. The negative electrode composite material includes a negative electrode active material or coated negative electrode active material and a solid electrolyte. The coated negative electrode active material may be coated active material particles according to this embodiment. The solid electrolyte between the positive electrode composite material and the negative electrode composite material may be the same or different.

[0093] The negative electrode current collector can be any conductive plate material; for example, a thin metal sheet (metal foil) such as copper or aluminum can be used. These are preferable because they have excellent resistance to electrolytes and oxidation.

[0094] The negative electrode layer may further contain, for example, a conductive material. The amount of conductive material may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of negative electrode active material or coated negative electrode active material. The conductive material may be the same as the conductive material used for the positive electrode.

[0095] The negative electrode layer may further contain, for example, a binder. The amount of binder may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of negative electrode active material or coated negative electrode active material. The same binder as the positive electrode binder described above may be used.

[0096] <Solid Electrolyte Layer> The solid electrolyte layer is interposed between the positive electrode layer and the negative electrode layer. The solid electrolyte layer separates the positive electrode layer from the negative electrode layer. The solid electrolyte layer contains a solid electrolyte. The solid electrolyte layer may further contain a binder. The solid electrolytes between the solid electrolyte layer and the positive electrode composite may be of the same type or different types. The solid electrolytes between the solid electrolyte layer and the negative electrode composite may be of the same type or different types.

[0097] The components of the lithium-ion secondary battery, such as the solid electrolyte layer, positive electrode layer, and negative electrode layer, are housed in a battery casing. While conventionally known materials can be used for the battery casing, specific examples include nickel-plated iron, stainless steel, aluminum or its alloys, nickel, titanium, resin materials, and film materials.

[0098] Lithium-ion secondary batteries come in various shapes, including coin-type, sheet-type (film-type), foldable, wound-type with a closed bottom, and button-type, and can be selected appropriately depending on the application.

[0099] The lithium-ion secondary battery according to this embodiment can achieve sufficient battery characteristics.

[0100] 《Method for Manufacturing Glass》 The method for manufacturing the glass that constitutes the glass solid electrolyte layer includes, as shown in Figure 1, the following steps 1 and 2 in order as steps S1 and S2. Step S1: Step 1: Heat a glass raw material mixture obtained by mixing each raw material containing Li, P, and S to obtain a molten product. Step S2: Step 2: Cool and solidify the molten product obtained in step 1 to obtain glass.

[0101] The heating in step 1 and the cooling in step 2 are carried out under atmospheric pressure conditions, and the cooling rate during solidification is 100°C / second or more. During cooling, the molten material is cooled uniformly and without thermal unevenness. This eliminates residues such as residual sulfur and unreacted raw materials, resulting in a homogeneous material with good water resistance. Furthermore, the wide range of vitrification and increased freedom in composition allow for the achievement of high lithium ion conductivity. In this specification, atmospheric pressure conditions mean a pressure range of approximately (gauge pressure ± 15 kPa). Gauge pressure means atmospheric pressure and is defined as 101.3 kPa in this specification.

[0102] In step 1 described above, the raw materials are mixed such that the resulting glass contains Li and P as elements constituting the cation component, and S as an element constituting the anion component, and its composition satisfies the requirements of Li: 30-42% and P: 5-16% in atomic percent.

[0103] Each step is explained below.

[0104] <Step 1> Step S1 in this embodiment is a step 1 in which each raw material is mixed to obtain a glass raw material mixture containing Li, P, and S, and then heated. Specifically, a glass raw material mixture is obtained by mixing a raw material containing Li, a raw material containing P, and a raw material containing S. Furthermore, if it is desired to obtain glass containing X as a constituent element, a raw material containing X is added to the raw material containing Li, a raw material containing P, and a raw material containing S, to obtain a glass raw material mixture containing Li, P, S, and X. Here, element X is at least one element selected from the group consisting of F, Cl, Br, and I.

[0105] Examples of raw materials containing the element Li include lithium sulfide (Li ２ S), Lithium carbonate (Li ２ CO ３ ), lithium sulfate (Li ２ SO ４ ), lithium oxide (Li ２ Examples include lithium compounds such as lithium hydroxide (LiOH) and metallic lithium. One or more Li-containing raw materials may be used. From the viewpoint of obtaining sulfide-based glass, lithium sulfide is preferred as the Li-containing raw material. Furthermore, if the resulting glass contains halogen elements, lithium halide (LiX, where X is a halogen element) is also preferred as the Li-containing raw material. Lithium halides will be discussed later.

[0106] Examples of raw materials containing element P include phosphorus pentasulfide (P ２ S ５ ), diphosphorus trisulfide (P ２ S ３ ) such as phosphorus sulfide, sodium phosphate (Na ３ PO ４ Examples include phosphorus compounds such as ) and elemental phosphorus. One type of raw material containing element P may be used, or two or more types may be used in combination. From the viewpoint of preventing the inclusion of elements other than those constituting the target glass, phosphorus sulfide is preferred as the raw material containing element P, and diphosphorus pentasulfide (P ２ S５ ) is more preferable. Furthermore, when using elemental phosphorus as a raw material containing element P, examples include yellow phosphorus, red phosphorus, violet phosphorus, black phosphorus, etc.

[0107] Examples of raw materials containing element S include lithium sulfide (Li ２ S), diphosphorus trisulfide (P ２ S ３ ), diphosphorus pentasulfide (P ２ S ５ Examples include phosphorus sulfide, other sulfur compounds containing phosphorus, and sulfur-containing compounds. Examples of sulfur-containing compounds include H ２ S, CS ２ , iron sulfide (FeS, Fe ２ S ３ FeS ２ Fe １－ｘ S, etc.), bismuth sulfide (Bi ２ S ３ ), copper sulfide (CuS, Cu ２ S, Cu １－ｘ Examples include S (such as sulfur). One type of raw material containing S may be used, or two or more types may be used in combination. From the viewpoint of preventing the inclusion of elements other than those constituting the target glass, lithium sulfide or phosphorus sulfide are preferred as raw materials containing S, and as phosphorus sulfide, diphosphorus pentasulfide (P ２ S ５ ) is more preferable. Note that lithium sulfide is a compound that contains both a Li element and a S element as raw materials, and phosphorus sulfide is a compound that contains both a S element and a P element as raw materials.

[0108] Examples of raw materials containing element X include lithium halides such as lithium fluoride (LiF), lithium chloride (LiCl), lithium bromide (LiBr), and lithium iodide (LiI), as well as phosphorus halides, phosphoryl halides, sulfur halides, sodium halides, and boron halides. One raw material containing element X may be used, or two or more may be used in combination. From the viewpoint of reactivity, lithium halides are preferred as raw materials containing element X, LiCl, LiBr, and LiI are more preferred, and LiBr and LiI are even more preferred.

[0109] Depending on the desired glass composition, other raw materials may be added to obtain a glass raw material mixture. For example, if the glass further contains at least one element selected from the group consisting of Sn, Sb, Si, Ge, Ga, Al, B, C, Mg, Ca, Sr, and Ba as elements constituting the cation component, raw materials containing those elements may be used. These raw materials are not limited to compounds, but may also be elemental metals.

[0110] If the glass further contains, in addition to X above, at least one element selected from the group consisting of O, Se, N, and C as an element constituting the anionic component, then raw materials containing those elements may also be used. These raw materials are not limited to compounds, but may also be elemental metals.

[0111] If the glass further contains other elements as mentioned above, raw materials containing Na, K, Y, Zr, Cr, Zn, Fe, Co, Ti, Mn, etc., may also be used. These other raw materials can be those that are conventionally known.

[0112] For example, raw materials containing the element Si include Si, SiO ２ SiS ２ Examples include SiS. Among them, from the viewpoint of lithium-ion conductivity, SiO ２ This is more preferable. These compounds may be used individually or in combination of two or more.

[0113] Raw materials containing the element Sn include Sn, SnS, and SnS ２ SnO, SnO ２ SnCl ２ These are some examples. In particular, from the viewpoint of lithium-ion conductivity, SnS ２ SnCl ２ Preferably, SnS ２ This is more preferable. These compounds may be used individually or in combination of two or more.

[0114] Examples of raw materials containing the element Sb include Sb, Sb ２ S ３ Sb ２ O ３ Sb ２ O ５ SbCl３ , SbCl ５ are exemplified. Among these, from the viewpoints of lithium ion conductivity and water resistance, Sb ２ S ３ , SbCl ３ are preferable, and Sb ２ S ３ is more preferable. These compounds may be used alone, or two or more thereof may be used in combination.

[0115] Examples of raw materials containing Ge element include Ge, GeO ２ , GeS, GeS ２ , GeCl ２ and the like. Among these, from the viewpoint of lithium ion conductivity, GeS ２ , GeCl ２ are preferable, and GeS ２ is more preferable. These compounds may be used alone, or two or more thereof may be used in combination.

[0116] Examples of raw materials containing Ga element include Ga, Ga ２ O ３ , Ga ２ S ３ , GaCl ３ and the like. Among these, from the viewpoint of lithium ion conductivity, Ga ２ S ３ , GaCl ３ are preferable, and Ga ２ S ３ is more preferable. These compounds may be used alone, or two or more thereof may be used in combination.

[0117] Examples of raw materials containing Al element include Al, Al ２ S ３ , Al ２ O ３ , AlCl ３ are exemplified. Among these, from the viewpoints of lithium ion conductivity and water resistance, Al ２ S ３ , AlCl ３ are preferable, and Al ２ S ３ is more preferable. These compounds may be used alone, or two or more thereof may be used in combination.

[0118] Examples of raw materials containing element B include B, B ２ O ３ , B ２ S ３ These are some examples. In particular, from the standpoint of the water resistance of glass, B ２ O ３ This is more preferable. These compounds may be used individually or in combination of two or more.

[0119] As a raw material containing element C, Li ２ CO ３ Li ２ C ２ CaCO ３ These are some examples. In particular, from the standpoint of availability and lithium-ion conductivity, Li ２ CO ３ This is preferable. These compounds may be used individually or in combination of two or more.

[0120] Raw materials containing the element Mg include Mg and MgO. ２ MgS, MgBr ２ MgI ２ These are some examples. In particular, from the viewpoint of ease of solubility, Mg and MgBr ２ Preferably, MgBr ２ This is more preferable. These compounds may be used individually or in combination of two or more.

[0121] Raw materials containing the element Ca include Ca and CaO. ２ CaS, CaBr ２ CaI ２ These are some examples. In particular, from the viewpoint of ease of solubility, CaBr ２ CaI ２ This is more preferable. These compounds may be used individually or in combination of two or more.

[0122] Raw materials containing the element Sr include Sr, SrO, SrS, and SrBr. ２ , SrI ２ These are some examples. In particular, from the viewpoint of ease of solubility, SrBr ２ , SrI ２ Preferably, SrI ２This is more preferable. These compounds may be used individually or in combination of two or more.

[0123] Raw materials containing the element Ba include Ba, BaO, BaS, and BaBr. ２ These are some examples. Among them, Ba is more preferred from the viewpoint of ease of solubility. These compounds may be used individually or in combination of two or more.

[0124] As raw materials containing element O, examples include oxides of the above-mentioned compounds, for example Li ２ O, Li ２ CO ３ , P ２ O ５ These are some examples. In particular, from the standpoint of productivity, Li ２ O, P ２ O ５ P is preferred. ２ O ５ This is more preferable. These compounds may be used individually or in combination of two or more.

[0125] Raw materials containing the element Se include Se, Li ２ Se, P ２ See ５ These are some examples. Among them, Se is preferred from the viewpoint of availability. These compounds may be used individually or in combination of two or more.

[0126] As a raw material containing N element, Li ３ N, LiNO ３ , P ３ N ５ These are some examples. In particular, from the perspective of procurement, Li ３ N, LiNO ３ Preferably, LiNO ３ This is more preferable. These compounds may be used individually or in combination of two or more.

[0127] These raw materials are blended appropriately according to the desired composition of the glass. Specifically, to obtain the glass described above, the raw materials are mixed so that they contain Li, P, and S, and satisfy at least Li: 30-42% and P: 5-16%. In addition to the above, preferred embodiments of the obtained glass are the same as those described above.

[0128] From the viewpoint of shortening the holding time during heating to obtain the molten material and from the viewpoint of glass homogeneity, it is preferable to reduce the particle size of each raw material. However, the manufacturing method according to this embodiment offers excellent composition control. Therefore, even if raw materials with particle sizes that may reduce homogeneity in conventional manufacturing methods are used, for example, the manufacturing method according to this embodiment can produce more homogeneous glass.

[0129] From the above viewpoint, specifically, the particle size of each raw material is preferably 1 mm or less, more preferably 500 μm or less, even more preferably 250 μm or less, even more preferably 100 μm or less, and particularly preferably 50 μm or less. Smaller particle sizes are preferable, but a practical lower limit is around 0.1 μm, although it may be 1 μm or more, or 5 μm or more. Furthermore, as described above, according to the manufacturing method of this embodiment, homogeneous glass can be easily obtained even when using raw materials with relatively large particle sizes. Taking this into consideration, for example from the viewpoint of suppressing manufacturing costs, the particle size of each raw material may be 10 μm or more, 100 μm or more, or 250 μm or more.

[0130] From these, the particle size of each raw material is preferably 0.1 μm to 1 mm, more preferably 1 to 500 μm, even more preferably 5 to 250 μm, even more preferably 5 to 100 μm, and particularly preferably 5 to 50 μm. Furthermore, from the viewpoint of manufacturing cost, the particle size of each raw material is preferably 10 μm to 1 mm, more preferably 100 μm to 1 mm, and even more preferably 250 to 500 μm. In this specification, the particle size of each raw material refers to the average particle diameter (D50) expressed as the median diameter obtained from the volume-based particle size distribution chart obtained by measuring the particle size distribution using a Microtrac MT3300EXII laser diffraction particle size distribution analyzer.

[0131] The raw materials can be mixed by methods such as mortar and pestle, media-based mixing such as a planetary ball mill, or media-less mixing such as a pin mill, powder agitator, or airflow mixing. The raw materials may be amorphous by mixing before heating.

[0132] The specific method for heating a glass raw material mixture to obtain a molten product is not particularly limited, other than performing the heating under atmospheric pressure conditions. In the manufacturing method according to this embodiment, the compositional deviation between the composition of the glass raw material mixture and the composition of the resulting glass is small because the heating for melting the glass raw material mixture is performed under atmospheric pressure conditions. Furthermore, the compositional deviation can be further suppressed by performing the heating under a gas atmosphere containing sulfur elements.

[0133] Here, atmospheric pressure conditions mean that the pressure inside the container during heating is within the range of (gauge pressure ± 15 kPa). That is, in the manufacturing method according to this embodiment, heating to obtain a molten product is carried out under atmospheric pressure conditions of (gauge pressure ± 15 kPa). The pressure during the above heating conditions may be any atmospheric pressure conditions of (gauge pressure ± 15 kPa), preferably (gauge pressure ± 10 kPa), more preferably (gauge pressure ± 5 kPa), and even more preferably (gauge pressure ± 2 kPa).

[0134] Furthermore, when heating the glass raw material mixture, it is preferable to adjust the addition ratio of Li and P in the glass raw material mixture so that the desired Li and P content ratio for the glass is achieved, taking into consideration, for example, that Li is an element that does not easily volatilize and P is an element that volatilizes easily. The manufacturing method according to this embodiment may be either a batch method or a continuous method.

[0135] Examples of heat-resistant containers for glass raw material mixtures include carbon heat-resistant containers, heat-resistant containers containing oxides such as quartz, quartz glass, borosilicate glass, aluminosilicate glass, alumina, zirconia, and mullite, heat-resistant containers containing nitrides such as silicon nitride and boron nitride, and heat-resistant containers containing carbides such as silicon carbide. Furthermore, these heat-resistant containers may be formed in bulk from the above materials, or they may be containers in which layers of carbon, oxides, nitrides, carbides, etc., are formed, such as carbon-coated quartz tubes.

[0136] The heating temperature when obtaining a molten glass raw material mixture varies depending on the raw materials used and the composition of the glass raw material mixture, but for example, 600 to 950°C is preferred, 630 to 850°C is more preferred, and 650 to 750°C is even more preferred. Here, from the viewpoint of reaction rate, the heating temperature is preferably 600°C or higher, more preferably 630°C or higher, and even more preferably 650°C or higher. Furthermore, from the viewpoint of suppressing compositional shifts due to volatilization of components, the above heating temperature is preferably 950°C or lower, more preferably 850°C or lower, and even more preferably 750°C or lower.

[0137] The heating time varies depending on the scale, but is preferably 10 minutes to 10 hours, more preferably 30 minutes to 9.5 hours, even more preferably 45 minutes to 9 hours, and particularly preferably 1 to 9 hours. From the viewpoint of ensuring the reaction proceeds well, the heating time is preferably 10 minutes or more, more preferably 30 minutes or more, even more preferably 45 minutes or more, and particularly preferably 1 hour or more. Also, from the viewpoint of productivity, the heating time is preferably 10 hours or less, more preferably 9.5 hours or less, and even more preferably 9 hours or less.

[0138] The atmosphere inside the container during heating is not particularly limited. For example, it may be under a nitrogen atmosphere, an argon atmosphere, or a gas atmosphere containing sulfur. Among these, a gas atmosphere containing sulfur is preferred from the viewpoint of more effectively suppressing compositional deviations.

[0139] When using a gas atmosphere containing sulfur, examples of sulfur sources include sulfur gas, hydrogen sulfide gas, and sulfur dioxide gas, and it is preferable to include sulfur gas from the viewpoint of reactivity with the glass raw material mixture. Alternatively, a gas containing sulfur may be introduced by adding elemental sulfur powder and vaporizing it by heating. Elemental sulfur powder may be added together with the raw materials when mixing them to obtain the glass raw material mixture, or it may be added separately after obtaining the glass raw material mixture. However, when elemental sulfur powder is added together with the raw materials when obtaining the glass raw material mixture, the mass of the elemental sulfur powder is not included in the mass of the obtained glass raw material mixture. In addition to introducing the above-mentioned sulfur gas, hydrogen sulfide gas, and sulfur dioxide gas as gases containing sulfur, a gas containing sulfur may also be introduced by adding elemental sulfur powder.

[0140] The gas containing element S is preferably used as a mixed gas with an inert gas, for example, the gas that serves as the source of element S. The mixing ratio with the inert gas is arbitrary and is not particularly limited as long as the cumulative amount of element S introduced relative to the mass of the glass raw material mixture can be set to a desired value.

[0141] Examples of the above-mentioned inert gases include nitrogen gas, argon gas, and helium gas, and these may be used individually or in mixtures of two or more.

[0142] The oxygen concentration in the atmosphere inside the container during heating is preferably 1000 ppm by volume or less.

[0143] The dew point during heating is preferably -20°C or lower, and although there is no particular lower limit, it is usually around -80°C.

[0144] In step 1, the melting of the glass raw material mixture can be confirmed by the absence of crystal-derived peaks in high-temperature X-ray diffraction measurements. It can also be confirmed by heating the molten material to a predetermined temperature and tilting it to check for fluidity.

[0145] <Step 2> Step S2 in this embodiment is Step 2, in which the molten material obtained in Step 1 is cooled and solidified to obtain glass.

[0146] Cooling and solidification are carried out under atmospheric pressure conditions. Here, atmospheric pressure conditions refer to an atmosphere under a pressure of approximately (gauge pressure ± 15 kPa), as mentioned above. The pressure used for cooling and solidification should be under atmospheric pressure conditions of (gauge pressure ± 15 kPa), preferably (gauge pressure ± 10 kPa), more preferably (gauge pressure ± 5 kPa), and even more preferably (gauge pressure ± 2 kPa).

[0147] The cooling rate in the cooling solidification process is 100°C / second or higher, preferably 100 to 100,000°C / second, more preferably 200 to 50,000°C / second, and even more preferably 300 to 10,000°C / second. Here, we have found that by using ultra-rapid cooling of 100°C / second or higher, which is faster than conventional methods, compositions that would conventionally result in crystal precipitation can be solidified as glass. This significantly increases the degree of freedom in composition, and allows for the selection of compositions that exhibit high lithium-ion conductivity.

[0148] Furthermore, by performing the above cooling and solidification process in a way that ensures the molten material is cooled uniformly and without thermal unevenness, a higher lithium-ion conductivity can be achieved compared to conventional glass. In addition, by performing the above cooling and solidification process under atmospheric pressure, the compositional deviation between the glass raw material mixture and the resulting glass can be minimized.

[0149] The above cooling rate is 100°C / second or higher, but from the viewpoint of ease of glass formation, 200°C / second or higher is preferred, and 300°C / second or higher is more preferred. Furthermore, there is no particular upper limit to the cooling rate, but from the viewpoint of equipment capacity, 100,000°C / second or lower is preferred, 50,000°C / second or lower is more preferred, and 10,000°C / second or lower is even more preferred. Such ultra-rapid cooling can be achieved, for example, by using a rapid cooling twin roll.

[0150] 《Method for Manufacturing Coated Active Material Particles》 The method for manufacturing coated active material particles according to this embodiment (hereinafter also referred to as "this manufacturing method") includes a step S11 in which a raw material mixture containing a raw material glass solid electrolyte and active material particles is dry-ground and mixed, as shown in Figure 2. This yields coated active material particles in which at least a portion of the surface of the active material particles is coated with a glass solid electrolyte layer. According to this manufacturing method, coated active material particles can be manufactured without heat treatment, which may degrade the performance of the active material particles. The composition and physical properties of the active material particles and the coated active material particles obtained by this manufacturing method are as described above.

[0151] <Raw material glass solid electrolyte> The raw material glass solid electrolyte used in this manufacturing method consists of the aforementioned glass. The above raw material glass solid electrolyte is dry-ground and mixed together with the active material particles to form the glass solid electrolyte layer of the coated active material particles.

[0152] The raw material glass solid electrolyte is obtained from the present glass. The method of preparing the raw material glass solid electrolyte is not particularly limited, as long as the average particle size is between 20 and 500 μm. One method of preparing the raw material glass solid electrolyte is to dry-grind the present glass using a ball mill and pass it through a 100-mesh (150 μm opening) sieve.

[0153] The average particle size of the raw glass solid electrolyte is 20 to 500 μm. From the viewpoint of ease of grinding, the above average particle size is 20 μm or more, preferably 40 μm or more, and more preferably 50 μm or more. Furthermore, the above average particle size is 500 μm or less, preferably 400 μm or less, and more preferably 300 μm or less.

[0154] The ratio of the volume of the raw glass solid electrolyte to the total volume of the active material particles and raw glass solid electrolyte contained in the raw material mixture is preferably 6 to 35 volume%. From the viewpoint of sufficiently coating the surface of the active material particles with the glass solid electrolyte layer, the above ratio is preferably 6 volume% or more, more preferably 9 volume% or more, and even more preferably 12 volume% or more. Furthermore, from the viewpoint of maintaining the charge and discharge capacity of the lithium-ion secondary battery using coated active material particles, the above ratio is preferably 35 volume% or less, more preferably 30 volume% or less, and even more preferably 25 volume% or less.

[0155] The content of active material particles in the raw material mixture is preferably 70 to 95% by mass. From the viewpoint of maintaining the charge and discharge capacity of lithium-ion secondary batteries using coated active material particles, the above content is preferably 70% by mass or more, more preferably 73% by mass or more, and even more preferably 76% by mass or more. Furthermore, from the viewpoint of sufficiently coating the surface of the active material particles with the glass solid electrolyte layer and more favorably realizing sufficient battery characteristics, the above content is preferably 95% by mass or less, more preferably 92% by mass or less, even more preferably 90% by mass or less, and particularly preferably 88% by mass or less.

[0156] The content of the raw material glass solid electrolyte in the raw material mixture is preferably 5 to 30% by mass. From the viewpoint of sufficiently coating the surface of the active material particles with the glass solid electrolyte layer and more favorably realizing sufficient battery characteristics, the above content is preferably 5% by mass or more, more preferably 7% by mass or more, even more preferably 10% by mass or more, and particularly preferably 12% by mass or more. Furthermore, from the viewpoint of maintaining the charge and discharge capacity of the lithium-ion secondary battery using coated active material particles, the above content is preferably 30% by mass or less, more preferably 27% by mass or less, and even more preferably 25% by mass or less.

[0157] The raw material mixture may contain other components in addition to the above-mentioned active material particles and raw material glass solid electrolyte. Examples of other components include those mentioned above in the section on "Coated Active Material Particles." Preferably, the raw material mixture contains a conductive additive as another component.

[0158] If the raw material mixture contains a conductive additive, its content is preferably greater than 0% by mass and 5% by mass or less. From the viewpoint of electron conductivity, the above content is preferably greater than 0% by mass, more preferably 0.1% by mass or more, even more preferably 0.3% by mass or more, and even more preferably 0.5% by mass or more. Furthermore, from the viewpoint of energy density, the above content is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 2% by mass or less.

[0159] The method of grinding and mixing in this manufacturing method is not particularly limited; mixing may be done using a mortar and pestle, or any mixing device or granulating device may be used.

[0160] The grinding and mixing time may be, for example, 0.1 to 24 hours. The above time is preferably 0.1 hours or more, more preferably 0.5 hours or more, even more preferably 1 hour or more, and preferably 24 hours or less, more preferably 15 hours or less, and even more preferably 10 hours or less.

[0161] The temperature during grinding and mixing may be, for example, 0 to 40°C. The above temperature is preferably 0°C or higher, more preferably 10°C or higher, preferably 40°C or lower, and more preferably 30°C or lower.

[0162] As described above, the following configurations are disclosed in this specification: [1] Coated active material particles comprising active material particles and a glass solid electrolyte layer, wherein at least a portion of the surface of the active material particles is coated with the glass solid electrolyte layer, and the glass solid electrolyte layer is made of glass that satisfies all of the following conditions (1) to (4): (1) The glass contains Li and P as elements constituting the cationic component and S as an element constituting the anionic component. (2) The composition of the glass satisfies Li: 30 to 42% and P: 5 to 16% in atomic percent. (3) The glass transition temperature of the glass is 110 to 300°C. (4) The lithium ion conductivity of the glass at 25°C is 2 mS / cm or more. [2] The coated active material particles according to [1], wherein the average particle size of the active material particles is 1 to 50 μm. [3] The coated active material particles according to [1] or [2], wherein the ratio of the volume of the glass solid electrolyte layer to the total volume of the active material particles and the glass solid electrolyte layer is 6 to 35 volume%. [4] The coated active material particles according to any one of [1] to [3], wherein the thickness of the glass solid electrolyte layer is 20 to 1000 nm. [5] The coated active material particles according to any one of [1] to [4], wherein the ratio of the thickness (μm) of the glass solid electrolyte layer to the average particle size (μm) of the active material particles is 0.02 to 0.4. [6] The coated active material particles according to any one of [1] to [5], further comprising more than 0 mass% and 5 mass% or less of a conductive additive. [7] The coated active material particles according to any one of [1] to [6], wherein the glass is amorphous. [8] An electrode mixture containing the coated active material particles according to any one of [1] to [7]. [9] A lithium-ion secondary battery containing the coated active material particles according to any one of [1] to [7].

[10] A method for producing coated active material particles, comprising dry grinding and mixing a raw material mixture containing a raw material glass solid electrolyte and active material particles, wherein the coated active material particles comprise the active material particles and a glass solid electrolyte layer, at least a portion of the surface of the active material particles is coated with the glass solid electrolyte layer, the average particle size of the raw material glass solid electrolyte is 20 to 500 μm, and the raw material glass solid electrolyte is made of glass that satisfies all of the following conditions (1) to (4).(1) The glass contains Li and P as elements constituting the cationic component, and S as an element constituting the anionic component. (2) The composition of the glass satisfies Li: 30 to 42% and P: 5 to 16% in atomic percent. (3) The glass transition temperature of the glass is 110 to 300°C. (4) The lithium ion conductivity of the glass at 25°C is 2 mS / cm or more.

[11] The method for producing coated active material particles according to

[10] , wherein the average particle size of the active material particles is 1 to 50 μm.

[12] The method for producing coated active material particles according to

[10] or

[11] , wherein the ratio of the volume of the glass solid electrolyte layer to the total volume of the active material particles and the glass solid electrolyte layer is 6 to 35 volume%.

[13] The method for producing coated active material particles according to any one of

[10] to

[12] , wherein the thickness of the glass solid electrolyte layer is 20 to 1000 nm.

[14] A method for producing coated active material particles according to any one of

[10] to

[13] , wherein the ratio of the thickness (μm) of the glass solid electrolyte layer to the average particle size (μm) of the active material particles is 0.02 to 0.4.

[15] A method for producing coated active material particles according to any one of

[10] to

[14] , wherein the raw material mixture further comprises a conductive additive in an amount of more than 0% by mass and 5% by mass or less.

[0163] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. Examples 1 to 5 are examples, and Example 6 is a comparative example.

[0164] <Test Examples> <Example 1> (Glass Preparation) Under a dry nitrogen gas atmosphere, 64.3 mol% lithium sulfide powder (manufactured by Albemarle, 99.9% purity), 21.4 mol% phosphorus pentasulfide powder (manufactured by Perimeter, 95-100% purity), 8.6 mol% lithium bromide powder (manufactured by Sigma-Aldrich, 99.995% purity), and 5.7 mol% lithium iodide powder (manufactured by Tokyo Chemical Industry Co., Ltd., 99.9% purity) were weighed and mixed in a mortar to obtain a glass raw material mixture. The obtained glass raw material mixture was placed in a carbon container under a nitrogen atmosphere with a dew point of -50°C or lower, containing sulfur powder (Sigma-Aldrich, 99.998% purity) as the S element source. The container was then placed in an electric furnace inside a glove box and heated for 1 hour at a pressure of gauge pressure + 1 kPa and a temperature of 750°C to obtain a molten material (Step 1). Next, the tip of the container was heated to melt it, and the molten material was flowed onto twin rolls at an outflow rate that would not cause temperature unevenness. The mixture was then cooled to room temperature at a cooling rate of 500°C / second to obtain glass (Step 2). The pressure at this time was (gauge pressure + 1 kPa), and the cooling rate was adjusted by the outflow rate of the molten material, the roll gap of the twin rolls, and the rotation speed.

[0165] (Preparation of Coated Active Material Particles) As the active material particles, cathode active material NCM622 (manufactured by JFE Mineral Co., Ltd., average particle size 9 μm) was used. As the raw material glass solid electrolyte, the glass prepared in (Preparation of Glass) above was dry-milled using a ball mill and passed through a 100-mesh (mesh opening 150 μm) sieve. The average particle size of the raw material glass solid electrolyte was 100 μm. The above active material particles and the raw material glass solid electrolyte were placed in a container in a mass ratio of 80:20 to make a raw material mixture. The raw material mixture was dry-milled and mixed for 3 hours. This yielded coated active material particles in which at least a portion of the surface of the active material particles was coated with a glass solid electrolyte layer.

[0166] (Fabrication of Lithium-ion Secondary Battery) The glass prepared in the above (Preparation of Glass) was dry-milled in a dry nitrogen atmosphere using a planetary ball mill (Ito Seisakusho Co., Ltd., model LP-M2) with alumina balls having a particle size of 2 mm. Next, it was passed through a sieve with a mesh size of 43 μm to obtain a sulfide-based solid electrolyte powder with an average particle size D50 of 3 μm. The coated active material particles prepared in the above (Preparation of Coated Active Material Particles) were used as the positive electrode active material. 80 mg of the sulfide-based solid electrolyte powder prepared above was placed in a 10 mm diameter plastic cylinder and molded under pressure to form a solid electrolyte layer. Next, 6 mg of the positive electrode active material prepared above was placed in the same cylinder and molded under pressure again to form a positive electrode layer. Furthermore, indium foil and lithium foil were placed on the opposite side of the positive electrode layer to form a negative electrode layer. In this way, an all-solid-state lithium-ion secondary battery was fabricated.

[0167] <Examples 2 and 3> In the above (fabrication of coated active material particles), glass, coated active material particles, and lithium-ion secondary batteries were fabricated in the same manner as in Example 1, except that the mass ratio of active material particles to raw glass solid electrolyte was changed as shown in Table 1.

[0168] <Examples 4 and 5> Except for using 50 mol% lithium sulfide powder, 17 mol% phosphorus pentasulfide powder, and 33 mol% lithium iodide powder in the above (preparation of glass) and changing the mass ratio of active material particles to raw glass solid electrolyte as shown in Table 1 in the above (preparation of coated active material particles), glass, coated active material particles, and lithium-ion secondary batteries were prepared in the same manner as in Example 1.

[0169] <Example 6> Except for using 70 mol% lithium sulfide powder and 30 mol% phosphorus pentasulfide powder as described above (for glass production), glass, coated active material particles, and a lithium-ion secondary battery were produced in the same manner as in Example 1.

[0170] 《Evaluation》 〈Glass Composition〉 The glass obtained in (Glass Preparation) was weighed in a glove box and dissolved in an alkaline aqueous solution, and the composition was analyzed element by element. The results are shown in Table 1. Specifically, P and S were analyzed by ICP emission spectrometry (instrument: Hitachi High-Tech Science, model PS3520UVDDII). Li was analyzed by atomic absorption spectrometry (instrument: Hitachi High-Tech, model ZA3300; CsCl was added to the solution concentration to 0.1% when measuring Li). Br and I were analyzed by ion chromatography (instrument: Thermo Fisher Scientific, model ICS-2100 (column: AS11HC), H ２ O ２ (A small amount was added and diluted with ultrapure water, and then measured.)

[0171] <Lithium-ion conductivity> The glass obtained in (glass production) was crushed in a mortar and then passed through a 100 μm sieve to obtain a powder with an average particle size (D50) of approximately 20 μm, which was used as the sample. The above sample was compacted into powder at a pressure of 380 MPa and used as the measurement sample, and measured using an AC impedance measuring device (Bio-Logic Sciences Instruments, potentiostat / galvanostat VSP). The measurement conditions were: measurement frequency: 100 Hz to 1 MHz, measurement voltage: 100 mV, measurement temperature: 25°C, and lithium-ion conductivity was determined from the obtained Nyquist plot. The results are shown in Table 1.

[0172] <Glass Transition Point> The glass obtained in (Glass Fabrication) was measured using differential scanning calorimetry (DSC) under conditions of 10°C / min. The temperature at the first inflection point of the obtained DSC chart was determined as the glass transition point. The results are shown in Table 1.

[0173] <Volume Ratio> The volume of the active material particles and the volume of the glass solid electrolyte layer in the obtained coated active material particles were measured by binarizing images obtained by SEM observation in an environment without exposure to air. The ratio of the volume of the glass solid electrolyte layer to the total volume of the active material particles and the glass solid electrolyte layer was calculated. The results are shown in Table 1.

[0174] <Thickness of the glass solid electrolyte layer> The thickness of the glass solid electrolyte layer in the coated active material particles obtained in Example 1 was measured by SEM. Specifically, the coated active material particles were cut in an air-free environment, the normal surface of the cut surface of the glass solid electrolyte layer was exposed using an ion milling apparatus, and the obtained sample was placed in an SEM using an air-free transfer vessel and measured by SEM observation. In the coated active material particles of Example 1, the thickness of the glass solid electrolyte layer was 700 nm, and the ratio of the thickness of the glass solid electrolyte layer (μm) to the average particle size (μm) of the active material particles was 0.08.

[0175] <Microscopic Observation> The obtained coated active material particles were subjected to microscopic observation. In Examples 1 to 6, the entire surface of the active material particles was coated with a glass solid electrolyte layer. Figure 3 shows images of the surface of the particles acquired by SEM during the preparation of the coated active material particles of Example 1. (a) to (d) are images acquired 5 minutes, 30 minutes, 1 hour, and 3 hours after the start of dry grinding and mixing of the raw material mixture, respectively. Figure 4 shows images of the surface of the coated active material particles obtained in Example 1, acquired by scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX). (a) is the image obtained by SEM observation. (b) to (f) are elemental mapping images of Co, S, P, O, and Ni respectively, acquired by EDX.

[0176] <Charge and Discharge Characteristics> Charge and discharge tests were conducted using the lithium-ion secondary batteries obtained in (Fabrication of Lithium-ion Secondary Batteries). For the charge and discharge tests, a constant current charge and discharge test was performed for 10 cycles under the following conditions: measurement temperature: 25°C, charging current density: 0.05C, discharging current density: 0.05C, charge and discharge potential range: 1.9 to 3.7V. Figure 5 shows the charge and discharge curve for the first cycle of the constant current charge and discharge test for the lithium-ion secondary battery fabricated using the coated active material particles of Example 1. Figure 6 shows the relationship between the number of cycles in the constant current charge and discharge test and the discharge capacity for the lithium-ion secondary battery fabricated using the coated active material particles of Example 1. Furthermore, Table 1 shows the initial discharge capacity measured for the lithium-ion secondary batteries obtained in each example.

[0177]

[0178] From the above results, the coated active material particles of Examples 1 to 5 according to this embodiment were able to achieve excellent initial discharge capacity when used in lithium-ion secondary batteries. On the other hand, in Example 6, the lithium-ion conductivity of the glass was low, and the initial discharge capacity when the coated active material particles were used in lithium-ion secondary batteries was also low.

[0179] As shown in Figure 5, the coated active material particles of Example 1 achieved sufficient battery characteristics, and as shown in Figure 6, the discharge characteristics did not deteriorate even after repeated cycles. Furthermore, as can be seen from Figure 3, by dry grinding and mixing the raw material mixture containing the raw glass solid electrolyte and active material particles, the raw glass solid electrolyte gradually formed a glass solid electrolyte layer, and the surface state of the active material particles gradually became smoother. In addition, as can be seen from Figure 4, S and P were thinly and uniformly distributed to coat the particles that are considered to be the active material particles (NCM622) based on the distribution of Ni, Co, and O. In other words, it was found that the surface of the active material particles was thinly and uniformly coated with a glass solid electrolyte layer.

[0180] Although the present invention has been described in detail with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications are possible without departing from the spirit and scope of the invention. This application is based on Japanese Patent Application No. 2025-031604, filed on 28 February 2025, which is incorporated herein by reference in its entirety.

Claims

1. Coated active material particles comprising active material particles and a glass solid electrolyte layer, wherein at least a portion of the surface of the active material particles is coated with the glass solid electrolyte layer, and the glass solid electrolyte layer is made of glass that satisfies all of the following conditions (1) to (4): (1) The glass contains Li and P as elements constituting the cationic component, and S as an element constituting the anionic component. (2) The composition of the glass satisfies Li: 30 to 42% and P: 5 to 16% in atomic percent. (3) The glass transition temperature of the glass is 110 to 300°C. (4) The lithium ion conductivity of the glass at 25°C is 2 mS / cm or more.

2. The coated active material particles according to claim 1, wherein the average particle size of the active material particles is 1 to 50 μm.

3. The coated active material particles according to claim 1 or 2, wherein the ratio of the volume of the glass solid electrolyte layer to the total volume of the active material particles and the glass solid electrolyte layer is 6 to 35% by volume.

4. The coated active material particle according to claim 1 or 2, wherein the thickness of the glass solid electrolyte layer is 20 to 1000 nm.

5. The coated active material particles according to claim 1 or 2, wherein the ratio of the thickness (μm) of the glass solid electrolyte layer to the average particle size (μm) of the active material particles is 0.02 to 0.

4.

6. Coated active material particles according to claim 1 or 2, further comprising more than 0% by mass and 5% by mass or less of a conductive additive.

7. The coated active material particles according to claim 1 or 2, wherein the glass is amorphous.

8. An electrode mixture comprising coated active material particles according to claim 1 or 2.

9. A lithium-ion secondary battery comprising coated active material particles according to claim 1 or 2.

10. A method for producing coated active material particles, comprising dry grinding and mixing a raw material mixture containing a raw material glass solid electrolyte and active material particles, wherein the coated active material particles comprise the active material particles and a glass solid electrolyte layer, and at least a portion of the surface of the active material particles is coated with the glass solid electrolyte layer, the average particle size of the raw material glass solid electrolyte is 20 to 500 μm, and the raw material glass solid electrolyte consists of glass that satisfies all of the following conditions (1) to (4): (1) The glass contains Li and P as elements constituting the cationic component, and S as an element constituting the anionic component. (2) The composition of the glass satisfies Li: 30 to 42% and P: 5 to 16% in atomic percent. (3) The glass transition temperature of the glass is 110 to 300°C. (4) The lithium ion conductivity of the glass at 25°C is 2 mS / cm or more.

11. The method for producing coated active material particles according to claim 10, wherein the average particle size of the active material particles is 1 to 50 μm.

12. The method for producing coated active material particles according to claim 10 or 11, wherein the ratio of the volume of the glass solid electrolyte layer to the total volume of the active material particles and the glass solid electrolyte layer is 6 to 35% by volume.

13. The method for producing coated active material particles according to claim 10 or 11, wherein the thickness of the glass solid electrolyte layer is 20 to 1000 nm.

14. The method for producing coated active material particles according to claim 10 or 11, wherein the ratio of the thickness (μm) of the glass solid electrolyte layer to the average particle size (μm) of the active material particles is 0.02 to 0.

4.

15. The method for producing coated active material particles according to claim 10 or 11, wherein the raw material mixture further comprises a conductive additive in an amount of more than 0% by mass and 5% by mass or less.

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