Method for manufacturing sulfide-based inorganic solid electrolyte materials

Abstract

To provide a method for producing a sulfide solid electrolyte material which can stably obtain a sulfide solid electrolyte material showing desired lithium ion conductivity.SOLUTION: A method for producing a sulfide-based inorganic solid electrolyte material containing lithium, phosphorus, and sulfur as constituent elements includes the steps of: heating a raw material composition containing diphosphorus pentasulfide, lithium sulfide, and lithium nitride to 40-220°C; vitrifying the raw material composition at lower than 50°C; and heating the obtained mixture in the glass state, and thereby crystallizing at least a part of the mixture.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a method for producing sulfide-based inorganic solid electrolyte materials. [Background technology]

[0002] Conventional lithium-ion batteries use electrolytes containing flammable organic solvents. Therefore, to enhance safety, development is underway to create all-solid-state lithium-ion batteries by replacing the electrolyte with a solid electrolyte. Furthermore, eliminating the need for flammable organic solvents allows for simplification of safety devices, resulting in improved manufacturing costs and productivity.

[0003] Examples of solid electrolyte materials used in such solid electrolytes include sulfide-based inorganic solid electrolyte materials.

[0004] Sulfide solid electrolyte materials can usually be obtained by amorphous treatment of the raw material composition. Examples of amorphous treatment include mechanical milling and melt-quenching, with mechanical milling being preferred. This is because mechanical milling allows for processing at room temperature, thus simplifying the manufacturing process. For example, Patent Document 1 discloses a method for obtaining a sulfide solid electrolyte material by amorphous treatment of a raw material composition containing Li2S and P2S5 by mechanical milling. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2021-82409 [Overview of the project] [Problems that the invention aims to solve]

[0006] P2S5, a raw material for sulfide solid electrolyte materials, is a compound of the allotropes P and S, and is the only compound among the many compounds with PS compositions that is industrially produced. Although P2S5 is industrially produced, heterogeneous reactions between P and S and slight differences in conditions during P2S5 crystallization can cause variations in the P and S composition ratio, and in some cases, polymers of phosphorus sulfide may be mixed in. Therefore, in the manufacturing method of sulfide solid electrolyte materials, P2S5 may be inactive in the raw material composition due to unavoidable factors.

[0007] The inventors have found that the reaction-inert P2S5 tends to prevent sufficient mechanochemical reactions in conventional mechanical milling, which can lead to significant variations in the lithium ion conductivity of the resulting sulfide solid electrolyte material. Therefore, the inventors focused on developing a sulfide solid electrolyte material that can stably exhibit a specified lithium ion conductivity by improving the reactivity of P2S5 with each raw material, and diligently conducted research. As a result, they discovered that a sulfide solid electrolyte material exhibiting the desired lithium ion conductivity can be stably obtained by applying an appropriate heat treatment to the raw material composition before mechanochemical treatment, thus completing the present invention.

[0008] The present invention has been made in view of the above circumstances, and provides a method for producing a sulfide-based inorganic solid electrolyte material that can stably obtain a sulfide-based inorganic solid electrolyte material exhibiting a desired lithium ion conductivity. [Means for solving the problem]

[0009] According to the present invention, A method for producing a sulfide-based inorganic solid electrolyte material containing lithium, phosphorus, and sulfur as constituent elements, A step of heating a raw material composition containing phosphorus pentasulfide, lithium sulfide, and lithium nitride to 40-220°C, A step of vitrifying the raw material composition when it reaches a temperature below 50°C, By heating the obtained glassy mixture, a step of crystallizing at least a part of the mixture is performed. A method for producing a sulfide-based inorganic solid electrolyte material containing is provided.

Advantages of the Invention

[0010] According to the present invention, a method for producing a sulfide-based inorganic solid electrolyte material can be provided, which can stably obtain a sulfide-based inorganic solid electrolyte material exhibiting a desired lithium ion conductivity.

Brief Description of the Drawings

[0011] [Figure 1] The figure is a cross-sectional view showing an example of the structure of a lithium ion battery according to an embodiment of the present invention.

Embodiments for Carrying Out the Invention

[0012] In this specification, the notation "a to b" in the description of a numerical range represents a to b, unless otherwise specified. For example, "1 to 5 mass%" means "1 mass% or more and 5 mass% or less".

[0013] Hereinafter, embodiments of the present invention will be described. The drawings are for illustrative purposes only. The shapes, dimensional ratios, etc. of each member in the drawings do not necessarily correspond to actual articles.

[0014] <Sulfide-based inorganic solid electrolyte material> The sulfide-based inorganic solid electrolyte material according to the present embodiment contains lithium (Li), phosphorus (P), and sulfur (S) as constituent elements from the viewpoint of further improving electrochemical stability, stability in moisture and air, and handleability, etc. Further, from the perspective of further improving lithium ion conductivity, electrochemical stability, stability in moisture and air, and handleability, etc. of the sulfide-based inorganic solid electrolyte material according to the present embodiment, the molar ratio Li / P of the content of Li to the content of P in the sulfide-based inorganic solid electrolyte material is preferably 1.0 or more and 5.0 or less, more preferably 2.0 or more and 4.0 or less, still more preferably 2.5 or more and 3.8 or less, even more preferably 2.8 or more and 3.6 or less, even more preferably 3.0 or more and 3.5 or less, even more preferably 3.1 or more and 3.4 or less, particularly preferably 3.1 or more and 3.3 or less. Also, the molar ratio S / P of the content of S to the content of P is preferably 2.0 or more and 6.0 or less, more preferably 3.0 or more and 5.0 or less, still more preferably 3.5 or more and 4.5 or less, even more preferably 3.8 or more and 4.2 or less, even more preferably 3.9 or more and 4.1 or less, particularly preferably 4.0.

[0015] Here, the contents of Li, P, and S in the sulfide-based inorganic solid electrolyte material according to the present embodiment can be determined by, for example, ICP emission spectroscopic analysis or X-ray analysis.

[0016] For the sulfide-based inorganic solid electrolyte material according to the present embodiment, in the spectrum obtained by X-ray diffraction using CuKα rays as the radiation source for the sulfide-based inorganic solid electrolyte material, the maximum diffraction intensity of the diffraction peak existing at the position (X) where the diffraction angle 2θ = 17.5 ± 0.3° is I x and the maximum diffraction intensity of the diffraction peak existing at the position (Y) where the diffraction angle 2θ = 29.4 ± 0.3° is I Y and the maximum diffraction intensity of the diffraction peak existing at the position (Z) where the diffraction angle 2θ = 32.5 ± 0.3° is I z When set as such, the value of I x / I Z is 2 or more, and / or the value of I Y / I Z is preferably 2 or more, and the value of I x / I Z is 3 or more, and / or the value of I Y / I ZIt is more preferable that the value of is 3 or higher. This makes it possible to obtain a sulfide-based inorganic solid electrolyte material with excellent lithium ion conductivity. In other words, the sulfide-based inorganic solid electrolyte material of this embodiment has its impurity generation suppressed during the manufacturing process.

[0017] Here, the diffraction peak located at the position (Z) with a diffraction angle of 2θ = 32.5 ± 0.3° is a peak originating from Li4P2S6, which has relatively low lithium ion conductivity. In other words, a small diffraction peak at the position (Z) with a diffraction angle of 2θ = 32.5 ± 0.3° indicates that the formation of Li4P2S6 is suppressed, resulting in good lithium ion conductivity. Therefore, in this embodiment, we focus on the diffraction peak located at the position (Z) with a diffraction angle of 2θ = 32.5 ± 0.3°, using the diffraction peaks at the position (X) with a diffraction angle of 2θ = 17.5 ± 0.3° and the diffraction peaks at the position (Y) with a diffraction angle of 2θ = 29.4 ± 0.3° as references, and I x / I Z The value of I Y / I Z It controls the value of [this value].

[0018] In the sulfide-based inorganic solid electrolyte material according to this embodiment, the lithium ion conductivity of the sulfide-based inorganic solid electrolyte material measured by AC impedance under measurement conditions of 27.0°C, applied voltage of 10mV, and measurement frequency range of 0.1Hz to 3MHz is preferably 0.5 × 10⁻⁶. -3 S·cm -1 The above is 0.6 × 10 -3 S·cm -1 More preferably 0.8 × 10 -3 S·cm -1 In addition, 1.0 × 10 is particularly preferred. -3 S·cm -1 That's all. If the lithium-ion conductivity of the sulfide-based inorganic solid electrolyte material according to this embodiment is above the above lower limit, a lithium-ion battery with even better battery characteristics can be obtained. Furthermore, using such a sulfide-based inorganic solid electrolyte material can yield a lithium-ion battery with even better input / output characteristics.

[0019] Examples of the shape of the sulfide-based inorganic solid electrolyte material according to this embodiment include particulate form. The particulate sulfide-based inorganic solid electrolyte material according to this embodiment is not particularly limited, but the average particle diameter d in the weight-based particle size distribution measured by laser diffraction scattering particle size distribution analysis is not limited. 50 However, it is preferably 1 μm to 100 μm, more preferably 3 μm to 80 μm, and even more preferably 5 μm to 60 μm. Average particle size d of sulfide-based inorganic solid electrolyte material 50 By keeping the range within the above limits, good handling performance can be maintained while further improving lithium-ion conductivity.

[0020] The sulfide-based inorganic solid electrolyte material according to this embodiment can be used in any application requiring lithium-ion conductivity. In particular, the sulfide-based inorganic solid electrolyte material according to this embodiment is preferably used in lithium-ion batteries. More specifically, it is used in the positive electrode active material layer, negative electrode active material layer, electrolyte layer, etc., in lithium-ion batteries. Furthermore, the sulfide-based inorganic solid electrolyte material according to this embodiment is suitably used in the positive electrode active material layer, negative electrode active material layer, solid electrolyte layer, etc., that constitute all-solid-state lithium-ion batteries, and is particularly suitably used in the solid electrolyte layer that constitutes all-solid-state lithium-ion batteries. An example of an all-solid-state lithium-ion battery using the sulfide-based inorganic solid electrolyte material according to this embodiment is one in which the positive electrode, the solid electrolyte layer, and the negative electrode are stacked in this order.

[0021] <Method for producing sulfide-based inorganic solid electrolyte materials> Next, a method for producing a sulfide-based inorganic solid electrolyte material according to this embodiment will be described. The method for producing a sulfide-based inorganic solid electrolyte material according to this embodiment is as follows: (Step 1) A step of heating a raw material composition containing phosphorus pentasulfide, lithium sulfide, and lithium nitride to 40-220°C, (Step 2) A step of vitrifying the raw material composition when it has reached a temperature below 50°C, (Step 3) A step of heating the resulting glassy mixture to crystallize at least a portion of the mixture, It includes, and further, (Step 4) The process may include crushing, classifying, or granulating the obtained sulfide-based inorganic solid electrolyte material. The details of each step are explained below.

[0022] (Process 1) First, a raw material composition is prepared containing phosphorus pentasulfide, lithium sulfide, and lithium nitride. Here, other phosphorus compounds besides phosphorus pentasulfide, lithium sulfide, and lithium nitride may be used in the raw material composition as appropriate, depending on the circumstances. However, the mixing ratio of each raw material in the raw material composition is adjusted so that the final sulfide-based inorganic solid electrolyte material has the desired composition ratio. For example, red phosphorus can be used as a phosphorus compound other than phosphorus pentasulfide. The method for mixing the raw materials is not particularly limited as long as it can uniformly mix the raw materials, but for example, mixing can be done using a ball mill, bead mill, vibratory mill, impact grinding device, mixer (pug mixer, ribbon mixer, tumbler mixer, drum mixer, V-type mixer, etc.), kneader, twin-screw kneader, air jet grinder, crusher, and rotary blade grinder. The mixing conditions, such as the stirring speed, processing time, temperature, reaction pressure, and gravitational acceleration applied to the mixture, can be appropriately determined depending on the volume of the mixture being processed.

[0023] The phosphorus pentasulfide used as a raw material may be of a molar ratio (S / P) of sulfur (S) content to phosphorus (P) content of 2.40 or more and 2.60 or less. From the viewpoint of further improving the time-dependent stability of the resulting sulfide-based inorganic solid electrolyte material, the lower limit of S / P is preferably 2.41 or higher, more preferably 2.42 or higher, and even more preferably 2.43 or higher, while preferably 2.58 or lower, 2.55 or lower, 2.50 or lower, 2.48 or lower, and 2.47 or lower, in that order. In this embodiment, the phosphorus pentasulfide has an S / P ratio within the above range, which improves the lithium ion conductivity of the resulting sulfide-based inorganic solid electrolyte material. In this embodiment, phosphorus pentasulfide having an S / P ratio within the above range can be obtained, for example, by reducing the amount of sulfur component in the phosphorus pentasulfide composition by vacuum heating of the phosphorus pentasulfide raw material composition.

[0024] Furthermore, the phosphorus (P) and sulfur (S) content of diphosphorus pentasulfide can be determined, for example, by quantitative analysis using energy-dispersive X-ray spectroscopy (EDX).

[0025] One example of the properties of phosphorus pentasulfide according to this embodiment is that it is in powder form. Since the production of sulfide-based inorganic solid electrolyte materials, which will be described later, is generally carried out by a dry process, having phosphorus pentasulfide in powder form according to this embodiment makes the production of sulfide-based inorganic solid electrolyte materials easier.

[0026] The lithium sulfide used as a raw material is not particularly limited; commercially available lithium sulfide may be used, or lithium sulfide obtained by the reaction of lithium hydroxide and hydrogen sulfide may be used, for example. From the viewpoint of obtaining a high-purity sulfide-based inorganic solid electrolyte material and suppressing side reactions, it is preferable to use lithium sulfide with few impurities. In this embodiment, lithium sulfide also includes polysulfide.

[0027] Since lithium nitride, used as a raw material, releases nitrogen into the system as N2, using lithium nitride as a raw material inorganic compound makes it possible to increase only the Li composition in sulfide-based inorganic solid electrolyte materials that contain Li, P, and S as constituent elements. The lithium nitride used in this embodiment is not particularly limited, and commercially available lithium nitride (e.g., Li3N, etc.) may be used, or lithium nitride obtained by the reaction of metallic lithium (e.g., Li foil) with nitrogen gas may be used. From the viewpoint of obtaining a high-purity solid electrolyte material and suppressing side reactions, it is preferable to use lithium nitride with few impurities.

[0028] In this embodiment, the respective blending ratios of phosphorus pentasulfide, lithium sulfide, and lithium nitride in the raw material composition are adjusted as appropriate depending on the purpose. However, when the total amount of phosphorus pentasulfide, lithium sulfide, and lithium nitride in the raw material composition is 100 mol%, it is preferable that the lithium sulfide content is 35 mol% to 75 mol%, the phosphorus pentasulfide content is 15 mol% to 55 mol%, and the lithium nitride content is 0.1 mol% to 10 mol%.

[0029] Next, the prepared raw material composition is heated to 40-220°C. This suppresses the decrease in lithium ion conductivity due to excessive heating, while enabling the production of a sulfide-based inorganic solid electrolyte material with excellent lithium ion conductivity. The heating temperature can be adjusted as appropriate in conjunction with the heating time, but is preferably 50°C or higher, more preferably 60°C or higher, even more preferably 100°C or higher, and especially preferably 150°C or higher, from the viewpoint of shortening the heating time and increasing productivity. Note that the heating temperature refers to the set temperature of the heating furnace.

[0030] The heating time can be adjusted as appropriate in conjunction with the heating temperature, but it is preferably between 0.5 and 150 hours. For example, if the heating temperature is between 40 and 100°C, the heating time may be 2 hours or more, or even 50 hours or more. Also, for example, if the heating temperature is between 100 and 220°C, the heating time may be 100 hours or less, 50 hours or less, or 5 hours or less.

[0031] (Process 2) Next, when the temperature of the raw material composition, which has been heated to 40-220°C, drops below 50°C, the raw material composition is vitrified. The method for lowering the temperature of the raw material composition to below 50°C is not particularly limited; it may be left to stand naturally or cooled with air. The temperature of the raw material composition before vitrification should be below 50°C, and from the viewpoint of work efficiency, it is preferable that it be equivalent to room temperature. Furthermore, the temperature of the raw material composition can be measured by inserting a thermocouple into the powder of the raw material composition.

[0032] As a vitrification method, for example, the raw material composition is mechanically treated to chemically react the raw materials, phosphorus pentasulfide, lithium sulfide, and lithium nitride, thereby vitrifying and obtaining a sulfide-based inorganic solid electrolyte material in a glassy state.

[0033] Here, the mechanical treatment can be any method that allows for vitrification while causing a chemical reaction by mechanically colliding two or more inorganic compounds. Examples of mechanical treatments include mechanochemical treatment. Mechanochemical treatment is a method of vitrification that applies mechanical energy, such as shear force or impact force, to the target composition. Furthermore, in step 2, the mechanochemical treatment is preferably a dry mechanochemical treatment, as this makes it easier to achieve an environment where moisture and oxygen are removed at a high level. By using mechanochemical processing, each raw material can be mixed while being pulverized into fine particles, thereby increasing the contact area between each raw material. This promotes the reaction of each raw material, and thus the sulfide-based inorganic solid electrolyte material according to this embodiment can be obtained more efficiently.

[0034] Here, mechanochemical treatment is a method of vitrification in which mechanical energy such as shear force, impact force, or centrifugal force is applied to the material to be mixed. Examples of equipment for performing vitrification by mechanochemical treatment (hereinafter referred to as vitrification equipment) include crushing and dispersing machines such as ball mills, bead mills, vibratory mills, turbo mills, mechanofusions, disc mills, and roll mills; rotary and impact crushing devices consisting of a mechanism that combines rotation (shear stress) and impact (compressive stress), such as rock drills, rotary drills, and impact drivers; high-pressure gliding rolls; and vertical mills such as roller-type vertical mills and ball-type vertical mills. Among these, ball mills and bead mills are preferred, and ball mills are particularly preferred, from the viewpoint of being able to efficiently generate very high impact energy. Furthermore, from the standpoint of excellent continuous productivity, roll mills; rotary and impact grinding devices consisting of a mechanism that combines rotation (shear stress) and impact (compressive stress), such as rock drills, rotary hammers, and impact drivers; high-pressure gliding rolls; and vertical mills such as roller-type vertical mills and ball-type vertical mills are preferred.

[0035] The mixing conditions, such as rotation speed, processing time, temperature, reaction pressure, and gravitational acceleration applied to the raw material inorganic electrolyte composition during mechanical processing, can be appropriately determined depending on the type and amount of the raw material inorganic composition. Generally, the faster the rotation speed, the faster the glass formation rate, and the longer the processing time, the higher the conversion rate to glass. Normally, when X-ray diffraction analysis is performed using CuKα rays as the radiation source, if the diffraction peak originating from the raw materials disappears or decreases, it can be determined that the raw material composition of the sulfide-based inorganic solid electrolyte material has been vitrified, and the desired sulfide-based inorganic solid electrolyte material has been obtained.

[0036] (Step 3) Next, the resulting glassy mixture is heated to crystallize at least a portion of it. That is, at least a portion of the sulfide-based inorganic solid electrolyte material is crystallized to produce a glass-ceramic (also called crystallized glass) sulfide-based inorganic solid electrolyte material. This allows the sulfide-based inorganic solid electrolyte material according to this embodiment to be in a glass-ceramic state (crystallized glass state), and as a result, its lithium-ion conductivity can be further improved.

[0037] The heating temperature for the glassy mixture is preferably in the range of 230°C to 350°C, more preferably in the range of 250°C to 330°C, and even more preferably in the range of 270°C to 300°C. The heating time is not particularly limited as long as it is the time required to obtain a sulfide-based inorganic solid electrolyte material in the desired glass-ceramic state, but is, for example, in the range of 0.5 hours to 24 hours, and preferably 1 hour to 3 hours. The heating method is not particularly limited, but one example is the use of a firing furnace.

[0038] Furthermore, heating of the glassy mixture is preferably carried out under an inert gas atmosphere, for example. This prevents deterioration (e.g., oxidation) of the sulfide-based inorganic solid electrolyte material. Examples of inert gases used during heating include argon gas, helium gas, and nitrogen gas. These inert gases are preferably of high purity to prevent contamination of the product with impurities, and their dew point is preferably -30°C or lower, more preferably -70°C or lower, and particularly preferably -80°C or lower, in order to avoid contact with moisture. The method of introducing the inert gas into the mixing system is not particularly limited as long as the mixing system is filled with an inert gas atmosphere, but examples include purging the inert gas and continuously introducing a constant amount of inert gas.

[0039] The heating conditions, such as temperature and time, can be appropriately adjusted to optimize the properties of the sulfide-based inorganic solid electrolyte material according to this embodiment.

[0040] (Step 4) In the method for producing a sulfide-based inorganic solid electrolyte material according to this embodiment, the obtained sulfide-based inorganic solid electrolyte material may be further subjected to steps of pulverization, classification, or granulation, if necessary. For example, by pulverizing to produce fine particles and then adjusting the particle size through classification or granulation, a sulfide-based inorganic solid electrolyte material having a desired particle size can be obtained. The pulverization method is not particularly limited, and known pulverization methods such as mixers, air jet milling, mortars, rotary mills, and coffee mills can be used. Similarly, the classification method is not particularly limited, and known methods such as sieving can be used. These grinding or classification processes are preferably carried out under an inert gas atmosphere or a vacuum atmosphere, as this prevents contact with moisture in the air.

[0041] To obtain the sulfide-based inorganic solid electrolyte material according to this embodiment, it is important to appropriately adjust each of the above steps. However, the method for producing the sulfide-based inorganic solid electrolyte material according to this embodiment is not limited to the method described above, and the sulfide-based inorganic solid electrolyte material according to this embodiment can be obtained by appropriately adjusting various conditions.

[0042] <Lithium-ion battery> Figure 1 is a cross-sectional view showing an example of the structure of a lithium-ion battery 100 according to an embodiment of the present invention. The lithium-ion battery 100 according to this embodiment includes, for example, a positive electrode 110 containing a positive electrode active material layer 101, an electrolyte layer 120, and a negative electrode 130 containing a negative electrode active material layer 103. At least one of the positive electrode active material layer 101, the negative electrode active material layer 103, and the electrolyte layer 120 contains the sulfide-based inorganic solid electrolyte material according to this embodiment. The shape of the lithium-ion battery 100 according to this embodiment is not particularly limited and may be cylindrical, coin-shaped, prismatic, film-shaped, or any other shape.

[0043] The embodiments of the present invention have been described above, but these are merely examples, and various other configurations can also be adopted. It should be noted that the present invention is not limited to the embodiments described above, and any modifications, improvements, etc., that can achieve the objectives of the present invention are included in the present invention. Examples of reference formats are provided below. 1. A method for producing a sulfide-based inorganic solid electrolyte material containing lithium, phosphorus, and sulfur as constituent elements, A step of heating a raw material composition containing phosphorus pentasulfide, lithium sulfide, and lithium nitride to 40-220°C, A step of vitrifying the raw material composition when it reaches a temperature below 50°C, A step of heating the resulting glassy mixture to crystallize at least a portion of the mixture, A method for producing a sulfide-based inorganic solid electrolyte material, including [the specified element]. 2. A method for producing a sulfide-based inorganic solid electrolyte material as described in 1., The step of vitrifying the mixture is, A method for producing a sulfide-based inorganic solid electrolyte material, comprising vitrifying the mixture by mechanical milling. 3. A method for producing a sulfide-based inorganic solid electrolyte material as described in 1. or 2., The step of crystallizing at least a portion of the glassy mixture is, A method for producing a sulfide-based inorganic solid electrolyte material, comprising heating the mixture at 230 to 350°C under an inert gas atmosphere. 4. A method for producing a sulfide-based inorganic solid electrolyte material as described in any one of 1 to 3, In the spectrum obtained by X-ray diffraction using CuKα rays as the source for the aforementioned sulfide-based inorganic solid electrolyte material, The maximum diffraction intensity of the diffraction peak located at the position (X) with a diffraction angle of 2θ = 17.5 ± 0.3° is defined as I. x Let I be the maximum diffraction intensity of the diffraction peak located at the position (Y) with a diffraction angle of 2θ = 29.4 ± 0.3°. Y Let I be the maximum diffraction intensity of the diffraction peak located at the position (Z) with a diffraction angle of 2θ = 32.5 ± 0.3°. z In that case, I x / I Z The value of is 2 or greater, and / or I Y / I Z A method for producing a sulfide-based inorganic solid electrolyte material in which the value of is 2 or greater. 5. A method for producing a sulfide-based inorganic solid electrolyte material as described in any one of 1 to 4, A method for producing a sulfide-based inorganic solid electrolyte material, wherein the step of heating the raw material composition is 0.5 to 150 hours. 6. A method for producing a sulfide-based inorganic solid electrolyte material as described in any one of items 1 to 5, When the total amount of phosphorus pentasulfide, lithium sulfide, and lithium nitride in the raw material composition is 100 mol%, The lithium sulfide content is 35 mol% or more and 75 mol% or less. The phosphorus pentasulfide content is 15 mol% or more and 55 mol% or less. The lithium nitride content is 0.1 mol% or more and 10 mol% or less. A method for producing sulfide-based inorganic solid electrolyte materials. 7. A method for producing a sulfide-based inorganic solid electrolyte material as described in any one of 1 to 6, The aforementioned phosphorus pentasulfide has a molar ratio (S / P) of sulfur (S) content to phosphorus (P) content of 2.40 or more and 2.60 or less. A method for producing sulfide-based inorganic solid electrolyte materials. 8. A method for producing a sulfide-based inorganic solid electrolyte material as described in any one of items 1 to 7, The sulfide-based inorganic solid electrolyte material is used in lithium-ion batteries. [Examples]

[0044] The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited thereto.

[0045] <Measurement method> The measurement methods in the following examples and comparative examples will be explained.

[0046] (1) X-ray diffraction analysis The diffraction spectra of the sulfide-based inorganic solid electrolyte materials obtained in the examples and comparative examples were determined by X-ray diffraction analysis using an X-ray diffractometer (Rigaku Corporation, RINT2000). CuKα radiation was used as the radiation source. The maximum diffraction intensity of the diffraction peak located at the position (X) with a diffraction angle of 2θ = 17.5 ± 0.3° is defined as I. x Let I be the maximum diffraction intensity of the diffraction peak located at the position (Y) with a diffraction angle of 2θ = 29.4 ± 0.3°. Y Let I be the maximum diffraction intensity of the diffraction peak located at the position (Z) with a diffraction angle of 2θ = 32.5 ± 0.3°. z That's what I decided.

[0047] (2) Measurement of lithium ion conductivity The lithium ion conductivity of the sulfide-based inorganic solid electrolyte materials obtained in the examples and comparative examples was measured using the AC impedance method. Lithium ion conductivity was measured using a potentiostat / galvanostat SP-300 manufactured by Hokuto Denko Co., Ltd. The sample size was φ9.5 mm and thickness 1.3 mm. The measurement conditions were: applied voltage 10 mV, measurement temperature 27.0 °C, measurement frequency range 0.1 Hz to 3 MHz, and lithium foil electrodes. Here, as the sample for lithium ion conductivity measurement, a 1.3 mm thick plate-shaped sulfide-based inorganic solid electrolyte material was used, obtained by pressing the powdered sulfide-based inorganic solid electrolyte material obtained in the examples and comparative examples at 270 MPa for 10 minutes using a press device.

[0048] (3) Determination of phosphorus (P) and sulfur (S) in diphosphorus pentasulfide The phosphorus pentasulfide compositions used in the examples and comparative examples were subjected to semi-quantitative analysis of phosphorus and sulfur by energy-dispersive X-ray spectroscopy (EDX). First, particles larger than 0.5 mm were selected from phosphorus pentasulfide in an argon atmosphere and crushed by lightly pressing with a pestle. Next, the crushed phosphorus pentasulfide composition was fixed to the sample base of a scanning electron microscope (Hitachi S-4700) using carbon conductive tape, with the flat surface created by the crushing facing upwards. Gold was then deposited by sputtering to ensure a conductive path between the base and the crushed material. This procedure aimed to stabilize the image by suppressing charge-up and to promote the detection of characteristic X-rays. The flat surface of the crushed phosphorus pentasulfide composition was observed at an electron beam acceleration voltage of 15 kV, emission current of 10 ± 1 μA, work distance of 12 mm, and magnification of 500x to confirm that it was a smooth surface. Then, semi-quantitative analysis of phosphorus (P) and sulfur (S) was performed using an energy-dispersive analyzer (Horiba EMAX-7000). Semi-quantitative analysis was performed using an electron beam acceleration voltage of 15kV, an electron beam incidence angle of 90°, an X-ray extraction angle of 35°, a pulse processing time of P3, and a dead time of 10-30%, measuring characteristic X-rays for 300 seconds. Quantitative conditions included setting background points to 0.67, 1.14, 1.70, 2.86, and 4.04 keV. Quantitative correction method: standardless φ(ρz), peak separation method: overlap factor method, no mass concentration normalization, no atomic number normalization, and no low-energy GB correction. Phosphorus (P) and sulfur (S) concentrations were measured from an observation field of 0.25 mm × 0.17 mm at five arbitrary locations on the flat surface of the crushed phosphorus pentasulfide composition, and the average values ​​were adopted.

[0049] <Example 1> Sulfide-based inorganic solid electrolyte materials were prepared using the following procedure. The raw materials used were P2S5 (PerimeterSolutions, Normal / S, S / P ratio 2.47), Li2S (Furukawa Machinery & Metal Co., Ltd., purity 99.9%), and Li3N (Furukawa Machinery & Metal Co., Ltd.). All work was carried out under an Ar atmosphere. The raw material composition was prepared by mixing a total of 3.0 g of Li2S powder, P2S5 powder, and Li3N powder (Li2S:P2S5:Li3N = 37.5:60.4:2.1 (by weight)) using a mortar and pestle. Next, 2.5 g of the raw material composition was placed in a carbon crucible and heated in a furnace at 120°C for 2.5 hours. 2.1 g of the resulting heat-treated raw material composition was subjected to mechanochemical treatment for 30 hours using a planetary ball mill (45 mL zirconia pot, 18 10 mm diameter zirconia balls). This treatment involved mechanical milling at 400 rpm for 10 minutes, followed by a 5-minute resting period, repeated 120 times, with the pot wall and ball-adhering powder scraped off after 15 hours. The resulting mixture was then placed in a carbon crucible and heated in a furnace at 290°C for 2 hours to obtain a sulfide-based inorganic solid electrolyte material. The above measurements were performed using the obtained sulfide-based inorganic solid electrolyte material. The results are shown in Table 1.

[0050] <Example 2> A sulfide inorganic solid electrolyte material was prepared in the same manner as in Example 1, except that the heat treatment temperature of the raw material composition was changed to 200°C, and each measurement was performed. The results are shown in Table 1.

[0051] <Example 3> A sulfide inorganic solid electrolyte material was prepared in the same manner as in Example 1, except that the heat treatment temperature of the raw material composition was changed to 210°C, and each measurement was performed. The results are shown in Table 1.

[0052] <Example 4> A sulfide inorganic solid electrolyte material was prepared in the same manner as in Example 1, except that the heat treatment temperature of the raw material composition was changed to 220°C, and each measurement was performed. The results are shown in Table 1.

[0053] <Example 5> A sulfide inorganic solid electrolyte material was prepared in the same manner as in Example 1, except that the heat treatment temperature of the raw material composition was changed to 60°C, and each measurement was performed. The results are shown in Table 1.

[0054] <Example 6> A sulfide inorganic solid electrolyte material was prepared in the same manner as in Example 1, except that the heat treatment temperature and time of the raw material composition were changed to 60°C and 63 hours, and each measurement was performed. The results are shown in Table 1.

[0055] <Example 7> A sulfide inorganic solid electrolyte material was prepared in the same manner as in Example 1, except that the raw material P2S5 (manufactured by PerimeterSolutions, Special / S, S / P ratio 2.52) was changed, and each measurement was performed. The results are shown in Table 1.

[0056] <Example 8> A sulfide inorganic solid electrolyte material was prepared in the same manner as in Example 1, except that the raw material P2S5 (manufactured by Kanto Chemical Co., Ltd., S / P ratio 2.59) was changed, and each measurement was performed. The results are shown in Table 1.

[0057] <Example 9> A sulfide inorganic solid electrolyte material was prepared in the same manner as in Example 1, except that the heat treatment temperature and time of the raw material composition were changed to 50°C and 63 hours, and each measurement was performed. The results are shown in Table 1.

[0058] <Comparative Example 1> A sulfide inorganic solid electrolyte material was prepared in the same manner as in Example 1, except that the raw material composition was not subjected to heat treatment, and each measurement was performed. The results are shown in Table 1.

[0059] <Comparative Example 2> A sulfide inorganic solid electrolyte material was prepared in the same manner as in Example 1, except that the heat treatment temperature of the raw material composition was changed to 230°C, and each measurement was performed. The results are shown in Table 1.

[0060] <Comparative Example 3> A sulfide inorganic solid electrolyte material was prepared in the same manner as in Example 1, except that the heat treatment temperature of the raw material composition was changed to 250°C, and each measurement was performed. The results are shown in Table 1.

[0061] <Comparative Example 4> A sulfide inorganic solid electrolyte material was prepared in the same manner as in Example 1, except that the raw material P2S5 (manufactured by PerimeterSolutions, Special / S, S / P ratio 2.52) was changed without heat treatment of the raw material composition, and each measurement was performed. The results are shown in Table 1.

[0062] <Comparative Example 5> A sulfide inorganic solid electrolyte material was prepared in the same manner as in Example 1, except that the raw material P2S5 (manufactured by Kanto Chemical Co., Ltd., S / P ratio 2.59) was changed without heat treatment of the raw material composition, and each measurement was performed. The results are shown in Table 1.

[0063] [Table 1] [Explanation of Symbols]

[0064] 100 Lithium-ion batteries 101 Cathode active material layer 103 Negative electrode active material layer 105 Current collector 110 Positive electrode 120 Electrolyte layer 130 negative electrode

Claims

1. A method for producing a sulfide-based inorganic solid electrolyte material containing lithium, phosphorus, and sulfur as constituent elements, A step of heating a raw material composition containing phosphorus pentasulfide, lithium sulfide, and lithium nitride to 40 to 220°C, A step of vitrifying the raw material composition when it reaches a temperature below 50°C, A step of heating the resulting glassy mixture to crystallize at least a portion of the mixture, Includes, A method for producing a sulfide-based inorganic solid electrolyte material, wherein the lithium ion conductivity of the sulfide-based inorganic solid electrolyte material is 0.5 × 10⁻³ S·cm⁻¹ or higher, measured by AC impedance under measurement conditions of 27.0°C, applied voltage of 10 mV, and measurement frequency range of 0.1 Hz to 3 MHz.

2. A method for producing a sulfide-based inorganic solid electrolyte material according to claim 1, The step of vitrifying the raw material composition is: A method for producing a sulfide-based inorganic solid electrolyte material, comprising vitrifying the raw material composition by mechanical milling.

3. A method for producing a sulfide-based inorganic solid electrolyte material according to claim 1 or 2, The step of crystallizing at least a portion of the glassy mixture is, A method for producing a sulfide-based inorganic solid electrolyte material, comprising heating the mixture at 230 to 350°C under an inert gas atmosphere.

4. A method for producing a sulfide-based inorganic solid electrolyte material according to any one of claims 1 to 3, In the spectrum obtained by X-ray diffraction using CuKα rays as the source for the aforementioned sulfide-based inorganic solid electrolyte material, The maximum diffraction intensity of the diffraction peak located at the position (X) with diffraction angle 2θ = 17.5 ± 0.3° is defined as I. ｘ Let I be the maximum diffraction intensity of the diffraction peak located at the position (Y) where the diffraction angle 2θ = 29.4 ± 0.3°. Ｙ Let I be the maximum diffraction intensity of the diffraction peak located at the position (Z) with a diffraction angle of 2θ = 32.5 ± 0.3°. ｚ In that case, I ｘ / I Ｚ The value of is 2 or greater, and / or I Ｙ / I Ｚ A method for producing a sulfide-based inorganic solid electrolyte material in which the value of is 2 or more.

5. A method for producing a sulfide-based inorganic solid electrolyte material according to any one of claims 1 to 4, A method for producing a sulfide-based inorganic solid electrolyte material, wherein the step of heating the raw material composition is 0.5 to 150 hours.

6. A method for producing a sulfide-based inorganic solid electrolyte material according to any one of claims 1 to 5, When the total amount of phosphorus pentasulfide, lithium sulfide, and lithium nitride in the raw material composition is 100 mol%, The lithium sulfide content is 35 mol% or more and 75 mol% or less. The phosphorus pentasulfide content is 15 mol% or more and 55 mol% or less. The lithium nitride content is 0.1 mol% or more and 10 mol% or less. A method for producing sulfide-based inorganic solid electrolyte materials.

7. A method for producing a sulfide-based inorganic solid electrolyte material according to any one of claims 1 to 6, The aforementioned phosphorus pentasulfide has a molar ratio (S / P) of sulfur (S) content to phosphorus (P) content of 2.40 or more and 2.60 or less. A method for producing sulfide-based inorganic solid electrolyte materials.

8. A method for producing a sulfide-based inorganic solid electrolyte material according to any one of claims 1 to 7, The sulfide-based inorganic solid electrolyte material is used in lithium-ion batteries.

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