JP7336833B2 - Sulfide-based inorganic solid electrolyte materials, solid electrolytes, solid electrolyte membranes, and lithium-ion batteries - Google Patents

Description

TECHNICAL FIELD The present invention relates to a sulfide-based inorganic solid electrolyte material, a solid electrolyte, a solid electrolyte membrane, and a lithium ion battery.

Lithium ion batteries are generally used as power sources for small portable devices such as mobile phones and notebook computers. Moreover, recently, lithium ion batteries have begun to be used as power sources for electric vehicles, power storage, and the like, in addition to small portable devices.

Lithium-ion batteries currently on the market use electrolytes containing flammable organic solvents. On the other hand, a lithium-ion battery in which the electrolytic solution is changed to a solid electrolyte to make the battery completely solid (hereinafter also referred to as an all-solid-state lithium-ion battery) does not use a flammable organic solvent in the battery, so it is a safety device. simplification, and is considered to be excellent in manufacturing cost and productivity.

As a solid electrolyte material used for such a solid electrolyte, for example, a sulfide-based inorganic solid electrolyte material is known.

Patent Document 1 (Japanese Patent Application Laid-Open No. 2016-27545) has a peak at a position of 2θ = 29.86° ± 1.00° in X-ray diffraction measurement using CuKα rays, and Li _2y+3 PS ₄ (0 .1≦y≦0.175).

JP 2016-27545 A

According to the studies of the present inventors, it has become clear that the lithium ion conductivity of the sulfide-based inorganic solid electrolyte material may gradually decrease when exposed to the atmosphere.
In other words, conventional sulfide-based inorganic solid electrolyte materials have room for improvement in terms of suppressing deterioration in lithium ion conductivity when exposed to the air.

The present invention has been made in view of the above circumstances, and provides a sulfide-based inorganic solid electrolyte material capable of suppressing a decrease in lithium ion conductivity when exposed to the atmosphere.

In order to provide a sulfide-based inorganic solid electrolyte material capable of suppressing a decrease in lithium ion conductivity when exposed to the atmosphere, the present inventors diligently studied the X-ray diffraction profile and the like of a sulfide-based inorganic solid electrolyte material. investigated. As a result, in the spectrum obtained by X-ray diffraction using CuKα rays as a radiation source, The present inventors have found that a sulfide-based inorganic solid electrolyte material having diffraction peaks and having a specific relationship between these diffraction peaks can suppress a decrease in lithium ion conductivity when exposed to the atmosphere, resulting in the present invention.

That is, according to the present invention,
A sulfide-based inorganic solid electrolyte material having lithium ion conductivity,
In the spectrum obtained by X-ray diffraction using CuKα rays as a radiation source, diffraction peaks are observed at diffraction angles 2θ = 17.2 ± 0.5° and 2θ = 18.8 ± 0.4°. have
Let I _B be the maximum diffraction intensity of the diffraction peak existing at the diffraction angle 2θ = 17.2 ± 0.5 °,
_{A sulfide-based inorganic solid electrolyte having a value of IC/IB of 0.27} or more, where IC is the maximum diffraction intensity of a diffraction peak present at a diffraction angle 2θ of 18.8±0.4°. Materials are provided.

Moreover, according to the present invention,
A sulfide-based inorganic solid electrolyte material having lithium ion conductivity,
After heat treatment at 270 ° C. for 2 hours, in the spectrum obtained by X-ray diffraction using CuKα rays as a radiation source, the position of the diffraction angle 2θ = 17.2 ± 0.5 ° and the diffraction angle 2θ = 18.8 ± Each has a diffraction peak at a position of 0.4 °,
Let I _B be the maximum diffraction intensity of the diffraction peak existing at the diffraction angle 2θ = 17.2 ± 0.5 °,
_{A sulfide-based inorganic solid electrolyte having a value of IC/IB of 0.27} or more, where IC is the maximum diffraction intensity of a diffraction peak present at a diffraction angle 2θ of 18.8±0.4°. Materials are provided.

Furthermore, according to the present invention,
A solid electrolyte containing the sulfide-based inorganic solid electrolyte material is provided.

Furthermore, according to the present invention,
A solid electrolyte membrane containing the solid electrolyte as a main component is provided.

Furthermore, according to the present invention,
A lithium ion battery comprising a positive electrode including a positive electrode active material layer, an electrolyte layer, and a negative electrode including a negative electrode active material layer,
At least one of the positive electrode active material layer, the electrolyte layer, and the negative electrode active material layer contains the sulfide-based inorganic solid electrolyte material.

According to the present invention, it is possible to provide a sulfide-based inorganic solid electrolyte material capable of suppressing a decrease in lithium ion conductivity when exposed to the atmosphere.

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which shows an example of the structure of the lithium ion battery of embodiment which concerns on this invention. FIG. 2 shows X-ray diffraction spectra of sulfide-based inorganic solid electrolyte materials obtained in Examples. FIG. 2 is a diagram showing an X-ray diffraction spectrum of a sulfide-based inorganic solid electrolyte material obtained in a comparative example;

An embodiment of the present invention will be described below with reference to the drawings. In addition, in all the drawings, the same constituent elements are denoted by the same reference numerals, and the explanation thereof is omitted as appropriate. Also, the drawings are schematic diagrams and do not correspond to actual dimensional ratios. The numerical range "A to B" represents from A to B unless otherwise specified.

[Sulfide-based inorganic solid electrolyte material]
First, the sulfide-based inorganic solid electrolyte material according to this embodiment will be described.
The sulfide-based inorganic solid electrolyte material according to the present embodiment is a sulfide-based inorganic solid electrolyte material having lithium ion conductivity, and in the spectrum obtained by X-ray diffraction using CuKα rays as a radiation source, the diffraction angle 2θ = 17.2 ± 0.5° and a diffraction angle 2θ = 18.8 ± 0.4°, respectively, and exist at a diffraction angle 2θ = 17.2 ± 0.5° When the maximum diffraction intensity of the diffraction peak at the diffraction angle 2θ=18.8±0.4° is defined as I _B and the maximum diffraction intensity of the diffraction peak existing at the diffraction angle 2θ=18.8±0.4° is defined as I _C , the value of I _C / _IB is It is 0.27 or more, preferably 0.35 or more, more preferably 0.40 or more, still more preferably 0.45 or more, even more preferably 0.50 or more, and particularly preferably 0.60 or more.
Although the upper limit of the value of I _C / _IB is not particularly limited, it is, for example, 2.0 or less, preferably 1.5 or less, more preferably 1.2 or less, and still more preferably 1.0 or less.
Further, the sulfide-based inorganic solid electrolyte material according to the present embodiment may have a structure in which the value of I _C / _IB is equal to or higher than the lower limit after being heat-treated at 270° C. for 2 hours. In this case, it is preferable to use the sulfide-based inorganic solid electrolyte material after heat-treating the sulfide-based inorganic solid electrolyte material so that the _IC / _IB value is equal to or higher than the lower limit.

The sulfide-based inorganic solid electrolyte material according to the present embodiment has a diffraction angle 2θ = 17.2 ± 0.5 ° and a diffraction angle 2θ = 18 in a spectrum obtained by X-ray diffraction using CuKα rays as a radiation source. Decrease in lithium ion conductivity when exposed to air due to having diffraction peaks at positions of 0.8±0.4° and having a value of I _C / _IB equal to or higher than the lower limit. can be suppressed.
Although the reason for this is not necessarily clear, the following reasons are presumed.
First, when the sulfide-based inorganic solid electrolyte material according to this embodiment is exposed to the air, the diffraction peak present at the diffraction angle 2θ=18.8±0.4° gradually disappears. Therefore, in the sulfide-based inorganic solid electrolyte material according to the present embodiment, the structure resulting from the diffraction peak existing at the diffraction angle 2θ = 18.8 ± 0.4 ° reacts with oxygen, moisture, etc. in the atmosphere. It is thought that this suppresses the decrease in lithium ion conductivity in the atmosphere. Therefore, it is considered that the sulfide-based inorganic solid electrolyte material according to the present embodiment can suppress a decrease in lithium ion conductivity when exposed to the air.
Therefore, in the spectrum obtained by X-ray diffraction using CuKα rays as a radiation source, diffraction is performed at a diffraction angle 2θ = 17.2 ± 0.5 ° and a diffraction angle 2θ = 18.8 ± 0.4 °. Having a peak and having a value of _IC / _IB equal to or higher than the lower limit indicates that a novel structure different from typical conventional sulfide-based inorganic solid electrolyte materials is formed. is thought to represent
In the present embodiment, in the spectrum obtained by X-ray diffraction using CuKα rays as the radiation source, the position of the diffraction angle 2θ = 17.2 ± 0.5 ° and the position of the diffraction angle 2θ = 18.8 ± 0.4 ° The sulfide-based inorganic solid electrolyte material having a diffraction peak at each and having a value of I _C / _IB equal to or higher than the lower limit has a composition ratio of the sulfide-based inorganic solid electrolyte material and an inorganic raw material In the step of vitrifying the composition, it is possible to prevent contact between moisture and oxygen and the inorganic composition at a higher level than before, and to perform heat treatment at a high temperature of 220° C. or higher.

The sulfide-based inorganic solid electrolyte material according to the present embodiment has a maximum diffraction intensity at a diffraction angle 2θ = 35.0 ± 0.1 ° in a spectrum obtained by X-ray diffraction using CuKα rays as a radiation source. When the ground intensity is I _A and the maximum diffraction intensity of the diffraction peak present at the diffraction angle 2θ=17.2±0.5° is I _B , the value of I _B / _IA is preferably 2.0 or more. , more preferably 3.0 or more, still more preferably 4.0 or more, and particularly preferably 5.0 or more.
Lithium ion conductivity can be further improved by setting the value of _IB / _IA to the above lower limit or more.
In addition, in the sulfide-based inorganic solid electrolyte material according to the present embodiment, the upper limit of the value of I _B /I _A is not particularly limited. It is 0 or less, more preferably 12.0 or less, and particularly preferably 9.0 or less.
Further, the sulfide-based inorganic solid electrolyte material according to the present embodiment may have a structure in which the value of I _B /I _A is within the above range after heat treatment at 270° C. for 2 hours.
The value of I _B / _IA of the sulfide-based inorganic solid electrolyte material according to the present embodiment is determined by the composition ratio of the sulfide-based inorganic solid electrolyte material and the process of vitrifying the inorganic composition as a raw material. This can be achieved by preventing contact between oxygen and the inorganic composition at a higher level than before, by performing heat treatment at a high temperature of 220° C. or higher, and the like.

The sulfide-based inorganic solid electrolyte material according to the present embodiment has a maximum diffraction intensity at a diffraction angle 2θ = 35.0 ± 0.1 ° in a spectrum obtained by X-ray diffraction using CuKα rays as a radiation source. When the ground intensity is I _A and the maximum diffraction intensity of the diffraction peak present at the diffraction angle 2θ=18.8±0.4° is I _C , the value of I _C /I _A is preferably 2.0 or more. , more preferably 3.0 or more, and still more preferably 4.0 or more.
By making the value of _IC / _IA equal to or higher than the above lower limit, it is possible to further suppress the decrease in lithium ion conductivity when exposed to the air.
In addition, in the sulfide-based inorganic solid electrolyte material according to the present embodiment, the upper limit of the value of I _C /I _A is not particularly limited, but is, for example, 30.0 or less, preferably 20.0 or less, more preferably 15.0. It is 0 or less, more preferably 10.0 or less, and particularly preferably 8.0 or less.
Further, the sulfide-based inorganic solid electrolyte material according to the present embodiment may have a structure in which the value of I _C /I _A is within the above range after heat treatment at 270° C. for 2 hours.
The value of I _C /I _A of the sulfide-based inorganic solid electrolyte material according to the present embodiment is determined by the composition ratio of the sulfide-based inorganic solid electrolyte material and the process of vitrifying the raw material inorganic composition. This can be achieved by preventing contact between oxygen and the inorganic composition at a higher level than before, by performing heat treatment at a high temperature of 220° C. or higher, and the like.

Further, in the sulfide-based inorganic solid electrolyte material according to the present embodiment, in the spectrum obtained by X-ray diffraction using CuKα rays as a radiation source, the position of the diffraction angle 2θ = 25.6 ± 0.5 °, the diffraction angle 2θ =26.6±0.4° and diffraction angle 2θ=29.2±0.8°. By having these diffraction peaks, the lithium ion conductivity can be further improved.
In addition, the sulfide-based inorganic solid electrolyte material according to the present embodiment is heat-treated at 270 ° C. for 2 hours, and then, in a spectrum obtained by X-ray diffraction using CuKα rays as a radiation source, the diffraction angle 2θ = 25.6 ± The configuration may further have diffraction peaks at a position of 0.5°, a diffraction angle of 2θ=26.6±0.4°, and a diffraction angle of 2θ=29.2±0.8°.

The sulfide-based inorganic solid electrolyte material according to the present embodiment contains Li, P and S as constituent elements from the viewpoint of further improving electrochemical stability, stability in moisture and air, handleability, etc. is preferred.
In addition, the sulfide-based inorganic solid electrolyte material according to the present embodiment further improves lithium ion conductivity, electrochemical stability, stability in moisture and air, handleability, etc., and the sulfide The molar ratio Li/P of the content of Li to the content of P in the inorganic solid electrolyte material is preferably 1.0 or more and 5.0 or less, more preferably 2.0 or more and 4.5 or less. , more preferably 3.0 or more and 4.2 or less, still more preferably 3.3 or more and 4.0 or less, particularly preferably 3.3 or more and 3.8 or less, and the above P content The molar ratio S/P of the S content to the amount is preferably 2.0 or more and 6.0 or less, more preferably 3.0 or more and 5.0 or less, and still more preferably 3.5 or more and 4 0.5 or less, and particularly preferably 3.8 or more and 4.2 or less.
Here, the contents of Li, P, and S in the sulfide-based inorganic solid electrolyte material according to this embodiment can be obtained by, for example, ICP emission spectroscopic analysis or X-ray analysis.

In the sulfide-based inorganic solid electrolyte material according to this embodiment, the lithium ion conduction of the sulfide-based inorganic solid electrolyte material by the AC impedance method under the measurement conditions of 27.0 ° C., an applied voltage of 10 mV, and a measurement frequency range of 0.1 Hz to 7 MHz. The degree is preferably 0.5×10 ⁻³ S·cm ⁻¹ or more, more preferably 0.6×10 ⁻³ S·cm ⁻¹ or more, and still more preferably 0.8×10 ⁻³ S·cm ^{− 1} or more, particularly preferably 1.0×10 ⁻³ S·cm ⁻¹ or more.
When the lithium ion conductivity of the sulfide-based inorganic solid electrolyte material according to the present embodiment is at least the above lower limit, a lithium ion battery with even better battery characteristics can be obtained. Furthermore, by using such a sulfide-based inorganic solid electrolyte material, it is possible to obtain a lithium ion battery with even better input/output characteristics.

The shape of the sulfide-based inorganic solid electrolyte material according to the present embodiment may be, for example, particulate.
The particulate sulfide-based inorganic solid electrolyte material according to the present embodiment is not particularly limited, but the average particle diameter _d50 in the weight-based particle size distribution by laser diffraction scattering particle size distribution measurement is preferably 1 μm or more and 100 μm or less. , more preferably 3 μm or more and 80 μm or less, still more preferably 5 μm or more and 60 μm or less.
By setting the average particle diameter _d50 of the sulfide-based inorganic solid electrolyte material within the above range, good handling properties can be maintained and lithium ion conductivity can be further improved.

The sulfide-based inorganic solid electrolyte material according to this embodiment preferably has excellent electrochemical stability. Here, the electrochemical stability refers to, for example, the property of being difficult to be oxidized and reduced in a wide voltage range. More specifically, in the sulfide-based inorganic solid electrolyte material according to the present embodiment, the sulfide-based inorganic solid electrolyte material measured under the conditions of a temperature of 25° C., a sweep voltage range of 0 to 5 V, and a voltage sweep rate of 5 mV / sec. is preferably 0.50 μA or less, more preferably 0.20 μA or less, even more preferably 0.10 μA or less, and even more preferably 0.05 μA or less. It is preferably 0.03 μA or less, and particularly preferably 0.03 μA or less.
When the maximum value of the oxidative decomposition current of the sulfide-based inorganic solid electrolyte material is equal to or less than the upper limit, oxidative decomposition of the sulfide-based inorganic solid electrolyte material in the lithium ion battery can be suppressed, which is preferable.
Although the lower limit of the maximum oxidative decomposition current of the sulfide-based inorganic solid electrolyte material is not particularly limited, it is, for example, 0.0001 μA or more.

The sulfide-based inorganic solid electrolyte material according to this embodiment can be used for any application that requires lithium ion conductivity. Among them, the sulfide-based inorganic solid electrolyte material according to the present embodiment is preferably used for lithium ion batteries. More specifically, it is used for positive electrode active material layers, negative electrode active material layers, electrolyte layers and the like in lithium ion batteries. Furthermore, the sulfide-based inorganic solid electrolyte material according to the present embodiment is suitably used for a positive electrode active material layer, a negative electrode active material layer, a solid electrolyte layer, etc. It is particularly suitably used for a solid electrolyte layer that constitutes a battery.
An example of an all-solid-state lithium ion battery to which the sulfide-based inorganic solid electrolyte material according to the present embodiment is applied is one in which a positive electrode, a solid electrolyte layer, and a negative electrode are laminated in this order.

[Method for producing sulfide-based inorganic solid electrolyte material]
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 different from the conventional method for producing a sulfide-based inorganic solid electrolyte material. That is, in the spectrum obtained by X-ray diffraction using CuKα rays as the radiation source, at the diffraction angle 2θ = 17.2 ± 0.5° and at the diffraction angle 2θ = 18.8 ± 0.4°. The sulfide-based inorganic solid electrolyte materials each having a diffraction peak and having an _IC / _IB value equal to or higher than the lower limit are (1) highly controlled composition ratios of the sulfide-based inorganic solid electrolyte materials. (2) in the step of vitrifying the raw material inorganic composition, preventing contact between moisture and oxygen and the inorganic composition at a higher level than before, (3) heating at a high temperature of 220 ° C. or higher. It can be obtained for the first time by adopting devised points on the manufacturing method such as processing.
Here, if the step (3) is performed, the film-forming properties of the sulfide-based inorganic solid electrolyte material may deteriorate, so the step (3) should be performed after the solid electrolyte membrane is formed. good too. That is, the sulfide-based inorganic solid electrolyte material according to the present embodiment also includes the sulfide-based inorganic solid electrolyte material in a state before performing the step (3).
However, on the premise that the sulfide-based inorganic solid electrolyte material according to the present embodiment employs the above-mentioned three manufacturing method contrivances, for example, specific manufacturing conditions such as mixing conditions of various raw materials are various. can be adopted.
Hereinafter, the method for producing the sulfide-based inorganic solid electrolyte material according to this embodiment will be described more specifically.

The sulfide-based inorganic solid electrolyte material according to this embodiment can be obtained, for example, by a production method including the following steps (A), (B) and (C). Moreover, the method for producing a sulfide-based inorganic solid electrolyte material according to the present embodiment may further include the following step (D), if necessary.
Step (A): Step of preparing a raw inorganic composition containing two or more raw inorganic compounds Step (B): Under an atmosphere in which the abundance and inflow of moisture and oxygen are suppressed to a higher level than before, A step of mechanically treating the raw material inorganic composition to vitrify the raw material inorganic compounds while chemically reacting with each other to obtain a sulfide-based inorganic solid electrolyte material in a vitreous state. Heating the sulfide-based inorganic solid electrolyte material to crystallize at least part of it Step (D): Pulverizing, classifying, or granulating the obtained sulfide-based inorganic solid electrolyte material

According to the method for producing a sulfide-based inorganic solid electrolyte material according to the present embodiment, the amount of moisture and oxygen present in the atmosphere, and the amount of moisture and oxygen in the atmosphere during the vitrification process, are greater than those of the conventional production method. Inflow is suppressed at a higher level than before. Therefore, according to the method for producing a sulfide-based inorganic solid electrolyte material according to the present embodiment, it is possible to suppress oxygen and moisture taken in during the production of the sulfide-based inorganic solid electrolyte material at a high level. It is considered that a sulfide-based inorganic solid electrolyte material having a novel structure different from that of the conventional method has been realized.

(Step (A) of preparing raw material inorganic composition)
First, a raw material inorganic composition containing two or more kinds of inorganic compounds such as lithium sulfide, phosphorus sulfide, and lithium nitride in a specific ratio is prepared. Here, the mixing ratio of each raw material in the raw material inorganic composition is adjusted so that the resulting sulfide-based inorganic solid electrolyte material has a desired composition ratio.
The method for mixing each raw material is not particularly limited as long as it is a mixing method that can uniformly mix each raw material. Mixer, V-type mixer, etc.), kneader, twin-screw kneader, pneumatic pulverizer, etc. can be used for mixing.
Mixing conditions such as stirring speed, treatment time, temperature, reaction pressure, and gravitational acceleration applied to the mixture when mixing the raw materials can be appropriately determined according to the throughput of the mixture.

Lithium sulfide used as a raw material is not particularly limited, and commercially available lithium sulfide may be used. For example, lithium sulfide obtained by reaction of lithium hydroxide and hydrogen sulfide may be used. From the viewpoint of obtaining a high-purity sulfide-based inorganic solid electrolyte material and from the viewpoint of suppressing side reactions, it is preferable to use lithium sulfide with few impurities.
Here, in this embodiment, lithium sulfide also includes lithium polysulfide.

Phosphorus sulfide used as _a raw material is not particularly limited, and commercially available phosphorus sulfides _{(eg, P2S5, P4S3, P4S7 , P4S5 , etc. ) can} be used. From the viewpoint of obtaining a high-purity sulfide-based inorganic solid electrolyte material and from the viewpoint of suppressing side reactions, it is preferable to use phosphorus sulfide with few impurities. In place of phosphorus sulfide, elemental phosphorus (P) and elemental sulfur (S) can also be used in a corresponding molar ratio. Elementary phosphorus (P) and elemental sulfur (S) can be used without particular limitation as long as they are industrially produced and sold.

Lithium nitride may be used as the raw material. Here, since nitrogen in lithium nitride is discharged into the system as _N2 , by using lithium nitride as an inorganic compound that is a raw material, a sulfide-based inorganic solid containing Li, P, and S as constituent elements It becomes possible to increase only the Li composition in the electrolyte material.
The lithium nitride according to the present embodiment is not particularly limited, and commercially available lithium nitride (e.g., Li ₃ N, etc.) may be used. For example, metal lithium (e.g., Li foil) and nitrogen gas Lithium nitride obtained by the reaction of may be used. From the viewpoint of obtaining a high-purity solid electrolyte material and from the viewpoint of suppressing side reactions, it is preferable to use lithium nitride with few impurities.

(Step (B) of obtaining a sulfide-based inorganic solid electrolyte material in a vitreous state)
Subsequently, by mechanically treating the raw material inorganic composition in an atmosphere in which the abundance and inflow of moisture and oxygen are suppressed to a higher level than before, the raw material inorganic compounds are vitrified while chemically reacting with each other. , to obtain a sulfide-based inorganic solid electrolyte material in a glassy state.

Here, the mechanical treatment is one in which two or more inorganic compounds are allowed to mechanically collide to vitrify while chemically reacting, and examples thereof include mechanochemical treatment. Here, the mechanochemical treatment is a method of vitrification while applying mechanical energy such as shear force or impact force to the target composition.
Moreover, in the step (B), the mechanochemical treatment is preferably a dry mechanochemical treatment from the viewpoint of easily realizing an environment in which moisture and oxygen are removed at a high level.
When the mechanochemical treatment is used, each raw material can be mixed while pulverized into fine particles, so that the contact area of each raw material can be increased. As a result, the reaction of each raw material can be promoted, so that the sulfide-based inorganic solid electrolyte material according to the present embodiment can be obtained more efficiently.

Here, the mechanochemical treatment is a method of vitrification while applying mechanical energy such as shear force, collision force or centrifugal force to the object to be mixed. Devices for vitrification by mechanochemical treatment (hereinafter referred to as vitrification devices) include crushing and dispersing machines such as ball mills, bead mills, vibration mills, turbo mills, mechanofusion, disc mills and roll mills; Rotary and impact pulverizers composed of mechanisms combining rotation (shear stress) and impact (compressive stress) represented by drills, impact drivers, etc.; high pressure type gliding rolls; and the like. 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. In addition, from the viewpoint of excellent continuous productivity, roll mills; rotary/impact pulverizers consisting of mechanisms that combine rotation (shear stress) and impact (compressive stress) represented by rock drills, vibration drills, impact drivers, etc. a high pressure type gliding roll; and the like.

In addition, in order to obtain the sulfide-based inorganic solid electrolyte material according to the present embodiment, it is important that the step (B) be performed in an atmosphere in which the abundance and inflow of moisture and oxygen are suppressed to a higher level than before. is. As a result, contact between the starting inorganic composition and moisture and oxygen can be suppressed at a higher level than before.
Here, an atmosphere in which the abundance and inflow of moisture and oxygen are suppressed to a higher level than before can be created by, for example, the following method.
First, the mixing vessel and the closed vessel for the vitrification apparatus are placed in the glove box, and then an inert gas such as high-purity dry argon gas or dry nitrogen gas obtained through the gas purification apparatus is applied to the inside of the glove box. Gas injection and vacuum degassing are performed multiple times (preferably three or more times). Here, in the glove box after the above operation, an inert gas such as high-purity dry argon gas or dry nitrogen gas is circulated through a gas purifier to reduce the oxygen concentration and water concentration to preferably 1.0 ppm or less, or more. It is preferably adjusted to 0.8 ppm or less, more preferably 0.6 ppm or less.
Next, two or more kinds of inorganic compounds are put into a mixing vessel in the glove box and then mixed to prepare a starting inorganic composition (meaning step (A)). Here, two or more kinds of inorganic compounds are introduced into the mixing container in the glove box by the following procedure. First, two or more kinds of inorganic compounds are put into the side box of the glove box with the door inside the main body of the glove box closed. Next, an inert gas such as high-purity dry argon gas or dry nitrogen gas introduced from the glove box is injected into the side box and vacuum deaeration is performed multiple times (preferably three times or more), and then open the door inside the main body of the glove box, put two or more inorganic compounds into the mixing container inside the main body of the glove box, and seal the mixing container;
Next, after mixing two or more kinds of inorganic compounds, the raw material inorganic composition obtained is taken out from the mixing container, transferred to a container for a vitrification apparatus, and sealed.
By performing such an operation, the amount of moisture and oxygen present in the closed container containing the starting inorganic composition can be suppressed to a higher level than before, and as a result, in the step (B), the amount of moisture and oxygen is reduced. It is possible to create an atmosphere in which the abundance is suppressed at a higher level than before.
Next, the sealed container containing the starting inorganic composition is taken out from the glove box. Next, the vitrification apparatus is placed in an atmosphere filled with dry gas such as dry argon gas, dry nitrogen gas, or dry air (for example, in a box filled with dry argon gas, dry nitrogen gas, dry air, etc.). Set the closed container in the container and vitrify it. Here, it is preferable to continue to introduce a constant amount of dry gas into the atmosphere filled with dry gas during vitrification. By taking such measures, it is possible to create an atmosphere in which the inflow of moisture and oxygen is suppressed at a higher level than before in the step (B).
In addition, from the viewpoint of suppressing the inflow of moisture and oxygen into the closed container at a high level, the lid part of the closed container is provided with O-rings, ferrule packing, etc., which have excellent sealing performance, from the viewpoint of achieving higher airtightness. is preferably used.

The mixing conditions such as rotation speed, treatment time, temperature, reaction pressure, and gravitational acceleration applied to the starting inorganic composition when mechanically treating the starting inorganic composition are appropriately determined depending on the type of starting inorganic composition and the treatment amount. be able to. In general, the faster the rotation speed, the faster the glass formation rate, and the longer the treatment time, the higher the conversion to glass.
Usually, when X-ray diffraction analysis is performed using CuKα rays as a radiation source, if the diffraction peak derived from the raw material disappears or decreases, the raw material inorganic composition is vitrified, and the desired sulfide-based inorganic solid electrolyte material is obtained. can be determined to be obtained.

Here, in the step (B), the lithium ion conductivity of the sulfide-based inorganic solid electrolyte material is preferably 1.0×10 ⁻⁴ S·cm ⁻¹ or more, more preferably 2.0×10 ⁻⁴ S·cm ⁻¹ or more, still more preferably 3.0×10 ⁻⁴ S·cm ⁻¹ or more, particularly preferably is preferably 4.0×10 ⁻⁴ S·cm ⁻¹ or more. This makes it possible to obtain a sulfide-based inorganic solid electrolyte material with even better lithium ion conductivity.

(Step (C) of crystallizing at least part of the sulfide-based inorganic solid electrolyte material)
Subsequently, by heating the obtained sulfide-based inorganic solid electrolyte material in a glassy state, at least part of the sulfide-based inorganic solid electrolyte material is crystallized to obtain a glass-ceramic state (also called crystallized glass). A sulfide-based inorganic solid electrolyte material is produced. By doing so, it is possible to obtain a sulfide-based inorganic solid electrolyte material with even better lithium ion conductivity.
That is, the sulfide-based inorganic solid electrolyte material according to the present embodiment is preferably in the glass-ceramics state (crystallized glass state) from the viewpoint of excellent lithium ion conductivity.

The temperature for heating the glassy sulfide-based inorganic solid electrolyte material is preferably in the range of 220° C. or higher and 500° C. or lower, and more preferably in the range of 250° C. or higher and 350° C. or lower.
The time for heating the sulfide-based inorganic solid electrolyte material in a glassy state is not particularly limited as long as the sulfide-based inorganic solid electrolyte material in a desired glass-ceramic state can be obtained. It is in the range of 1 hour or more and 24 hours or less, preferably 1 hour or more and 3 hours or less. Although the heating method is not particularly limited, for example, a method using a kiln can be mentioned. The conditions such as temperature and time for such heating can be appropriately adjusted in order to optimize the properties of the sulfide-based inorganic solid electrolyte material according to this embodiment.

Moreover, it is preferable to heat the glassy sulfide-based inorganic solid electrolyte material in, for example, an inert gas atmosphere. This makes it possible to prevent deterioration (for example, oxidation) of the sulfide-based inorganic solid electrolyte material.
Examples of the inert gas for heating the glassy sulfide-based inorganic solid electrolyte material include argon gas, helium gas, and nitrogen gas. These inert gases preferably have a high purity in order to prevent contamination of the product with impurities. °C or less is particularly preferred. The method of introducing the inert gas into the mixed system is not particularly limited as long as the inside of the mixed system is filled with an inert gas atmosphere. methods and the like.

(Step (D) of pulverizing, classifying, or granulating)
In the method for producing a sulfide-based inorganic solid electrolyte material according to the present embodiment, a step of pulverizing, classifying, or granulating the obtained sulfide-based inorganic solid electrolyte material may be further performed, if necessary. For example, a sulfide-based inorganic solid electrolyte material having a desired particle size can be obtained by finely pulverizing and then adjusting the particle size by classification or granulation. The pulverization method is not particularly limited, and known pulverization methods such as mixer, airflow pulverization, mortar, rotary mill, and coffee mill can be used. Moreover, the classification method is not particularly limited, and a known method such as a sieve can be used.
These pulverization or classification are preferably carried out under an inert gas atmosphere or a vacuum atmosphere from the viewpoint of preventing contact with moisture in the air.

In order to obtain the sulfide-based inorganic solid electrolyte material according to the present 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 the present embodiment is not limited to the above method, and by appropriately adjusting various conditions, the sulfide-based inorganic solid electrolyte material according to the present embodiment can be produced. A solid electrolyte material can be obtained.

[Solid electrolyte]
Next, the solid electrolyte according to this embodiment will be described. The solid electrolyte according to this embodiment includes the sulfide-based inorganic solid electrolyte material according to this embodiment.
The solid electrolyte according to the present embodiment is not particularly limited, but as a component other than the sulfide-based inorganic solid electrolyte material according to the present embodiment, for example, the above-described present embodiment within a range that does not impair the object of the present invention It may contain a solid electrolyte material of a different type from the sulfide-based inorganic solid electrolyte material according to .

The solid electrolyte according to this embodiment may contain a solid electrolyte material of a different type from the above-described sulfide-based inorganic solid electrolyte material according to this embodiment. The type of solid electrolyte material different from the sulfide-based inorganic solid electrolyte material according to the present embodiment is not particularly limited as long as it has ion conductivity and insulation, but is generally used for lithium ion batteries. can be used. For example, inorganic solid electrolyte materials such as sulfide-based inorganic solid electrolyte materials, oxide-based inorganic solid electrolyte materials, and other lithium-based inorganic solid electrolyte materials that are different from the sulfide-based inorganic solid electrolyte material according to the present embodiment; Organic solid electrolyte materials such as polymer electrolytes can be mentioned.

Examples of the sulfide-based inorganic solid electrolyte material different from the sulfide-based inorganic solid electrolyte material according to the present embodiment described above include Li ₂ SP ₂ S ₅ material, Li ₂ S-SiS ₂ material, Li ₂ S - _GeS2 material, _{Li2S - Al2S3} material _{, Li2S - SiS2} - _Li3PO4 material, _Li2SP2S5 - _GeS2 material _{, Li2S} - _{Li2OP 2S5 - SiS2} material, _Li2S - _GeS2 - _{P2S5 - SiS2} material _{, Li2S} - _SnS2 - _{P2S5 - SiS2} material, _{Li2SP2S5 -} Li _3N materials, Li ₂ S _2+X -P ₄ S ₃ materials, Li ₂ SP ₂ S ₅ -P ₄ S ₃ materials, and the like. These may be used individually by 1 type, and may be used in combination of 2 or more type.
Among these materials, the Li ₂ SP ₂ S ₅ material is preferable from the viewpoint of excellent lithium ion conductivity and stability that does not cause decomposition or the like in a wide voltage range. Here, for example, the Li ₂ SP ₂ S ₅ material is an inorganic material obtained by chemically reacting an inorganic composition containing at least Li ₂ S (lithium sulfide) and P ₂ S ₅ with each other by mechanical treatment. means material.
Here, in this embodiment, lithium sulfide also includes lithium polysulfide.

Examples of the oxide-based inorganic solid electrolyte material include NASICON type materials such as LiTi ₂ (PO ₄ ) ₃ , LiZr ₂ (PO ₄ ) ₃ , LiGe ₂ (PO ₄ ) ₃ , (La _{0.5 + x} Li _{0.5 -3x} ) Perovskite type such as TiO ₃ , Li ₂ O—P ₂ O ₅ materials, Li ₂ O—P ₂ O ₅ —Li ₃ N materials, and the like.
Examples of other lithium-based inorganic solid electrolyte materials include LiPON, LiNbO ₃ , LiTaO ₃ , Li ₃ PO ₄ , LiPO _4-x N _x (where x is 0<x≦1), LiN, LiI, LISICON, and the like. be done.
Furthermore, glass-ceramics obtained by depositing crystals of these inorganic solid electrolytes can also be used as inorganic solid electrolyte materials.

As the organic solid electrolyte material, for example, polymer electrolytes such as dry polymer electrolytes and gel electrolytes can be used.
As the polymer electrolyte, those generally used for lithium ion batteries can be used.

[Solid electrolyte membrane]
Next, the solid electrolyte membrane according to this embodiment will be described.
The solid electrolyte membrane according to this embodiment contains, as a main component, a solid electrolyte containing the above-described sulfide-based inorganic solid electrolyte material according to this embodiment.

The solid electrolyte membrane according to the present embodiment is used, for example, as a solid electrolyte layer that constitutes an all-solid-state lithium ion battery.
An example of an all-solid-state lithium ion battery to which the solid electrolyte membrane according to the present embodiment is applied is one in which a positive electrode, a solid electrolyte layer, and a negative electrode are laminated in this order. In this case, the solid electrolyte layer is composed of a solid electrolyte membrane.

The average thickness of the solid electrolyte membrane according to the present embodiment is preferably 5 μm or more and 500 μm or less, more preferably 10 μm or more and 200 μm or less, and still more preferably 20 μm or more and 100 μm or less. When the average thickness of the solid electrolyte membrane is equal to or greater than the lower limit, it is possible to further suppress the lack of the solid electrolyte and the occurrence of cracks on the surface of the solid electrolyte membrane. Moreover, the impedance of a solid electrolyte membrane can be further reduced as the average thickness of the said solid electrolyte membrane is below the said upper limit. As a result, the battery characteristics of the obtained all-solid-state lithium ion battery can be further improved.

The solid electrolyte membrane according to this embodiment is preferably a pressure-molded body of a particulate solid electrolyte containing the above-described sulfide-based inorganic solid electrolyte material according to this embodiment. That is, it is preferable to pressurize the particulate solid electrolyte to form a solid electrolyte membrane having a certain strength due to the anchoring effect between the solid electrolyte materials.
By forming a pressure-molded body, the solid electrolytes are bonded to each other, and the strength of the obtained solid electrolyte membrane is further increased. As a result, it is possible to further suppress the loss of the solid electrolyte and the occurrence of cracks on the surface of the solid electrolyte membrane.

The content of the sulfide-based inorganic solid electrolyte material according to the present embodiment in the solid electrolyte membrane according to the present embodiment is preferably 50% by mass or more, when the entire solid electrolyte membrane is 100% by mass. It is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more. As a result, the contact between the solid electrolytes is improved, and the interfacial contact resistance of the solid electrolyte membrane can be reduced. As a result, the lithium ion conductivity of the solid electrolyte membrane can be further improved. By using such a solid electrolyte membrane with excellent lithium ion conductivity, the battery characteristics of the obtained all-solid-state lithium ion battery can be further improved.
Although the upper limit of the content of the sulfide-based inorganic solid electrolyte material according to the present embodiment in the solid electrolyte membrane according to the present embodiment is not particularly limited, it is, for example, 100% by mass or less.

The planar shape of the solid electrolyte membrane is not particularly limited, and can be appropriately selected according to the shape of the electrode or current collector. For example, it can be rectangular.

Further, the solid electrolyte membrane according to the present embodiment may contain a binder resin, and the content of the binder resin is preferably less than 0.5% by mass when the solid electrolyte membrane as a whole is 100% by mass. , more preferably 0.1% by mass or less, still more preferably 0.05% by mass or less, and even more preferably 0.01% by mass or less. Further, the solid electrolyte membrane according to this embodiment preferably does not substantially contain a binder resin, and most preferably does not contain a binder resin.
As a result, the contact between the solid electrolytes is improved, and the interfacial contact resistance of the solid electrolyte membrane can be reduced. As a result, the lithium ion conductivity of the solid electrolyte membrane can be further improved. By using such a solid electrolyte membrane with excellent lithium ion conductivity, the battery characteristics of the obtained all-solid-state lithium ion battery can be improved.
The phrase "substantially free of binder resin" means that it may be contained to the extent that the effects of the present embodiment are not impaired. Further, when an adhesive resin layer is provided between the solid electrolyte layer and the positive electrode or the negative electrode, the adhesive resin derived from the adhesive resin layer present in the vicinity of the interface between the solid electrolyte layer and the adhesive resin layer is referred to as the "solid electrolyte It is excluded from "binder resin in the film".

The binder resin refers to a binder generally used in lithium ion batteries to bind between inorganic solid electrolyte materials. Examples include polyvinyl alcohol, polyacrylic acid, carboxymethylcellulose, polytetrafluoro Examples include ethylene, polyvinylidene fluoride, styrene-butadiene rubber, and polyimide.

The solid electrolyte membrane according to the present embodiment can be produced, for example, by depositing a particulate solid electrolyte on the cavity surface of the mold or on the surface of the base material in the form of a film, and then pressing the solid electrolyte deposited in the form of a film. Obtainable.
The method of pressurizing the solid electrolyte is not particularly limited. For example, when the particulate solid electrolyte is deposited on the cavity surface of the mold, pressing is performed using a mold and a pressing mold, and the particulate solid electrolyte is applied to the substrate surface. When it is deposited on the surface, press using a mold and stamping die, roll press, flat plate press, or the like can be used.
The pressure to pressurize the solid electrolyte is, for example, 10 MPa or more and 500 MPa or less.

In addition, if necessary, the inorganic solid electrolyte deposited in the form of a film may be pressurized and heated. If heat and pressure are applied, the solid electrolytes are fused and bonded to each other, and the strength of the obtained solid electrolyte membrane is further increased. As a result, it is possible to further suppress the loss of the solid electrolyte and the occurrence of cracks on the surface of the solid electrolyte membrane.
The temperature for heating the solid electrolyte is, for example, 40° C. or higher and 500° C. or lower.

[Lithium-ion battery]
FIG. 1 is a cross-sectional view showing an example of the structure of a lithium ion battery 100 according to an embodiment of the invention.
A lithium ion battery 100 according to the present embodiment includes, for example, a positive electrode 110 including a positive electrode active material layer 101 , an electrolyte layer 120 , and a negative electrode 130 including 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. Moreover, all of the positive electrode active material layer 101, the negative electrode active material layer 103, and the electrolyte layer 120 preferably contain the sulfide-based inorganic solid electrolyte material according to this embodiment. In this embodiment, a layer containing a positive electrode active material is referred to as a positive electrode active material layer 101 unless otherwise specified. The positive electrode 110 may further include a current collector 105 in addition to the positive electrode active material layer 101 or may not include the current collector 105 as necessary. In this embodiment, a layer containing a negative electrode active material is referred to as a negative electrode active material layer 103 unless otherwise specified. The negative electrode 130 may further include a current collector 105 in addition to the negative electrode active material layer 103 or may not include the current collector 105 as necessary.
The shape of the lithium-ion battery 100 according to this embodiment is not particularly limited, and may be cylindrical, coin-shaped, rectangular, film-shaped or any other shape.

The lithium ion battery 100 according to this embodiment is manufactured according to a generally known method. For example, the positive electrode 110, the electrolyte layer 120, and the negative electrode 130 are stacked to form a cylindrical shape, coin shape, square shape, film shape, or any other shape, and if necessary, by enclosing a non-aqueous electrolyte solution. produced.

(positive electrode)
The positive electrode 110 is not particularly limited, and one commonly used in lithium ion batteries can be used. Although the positive electrode 110 is not particularly limited, it can be manufactured according to a generally known method. For example, it can be obtained by forming a positive electrode active material layer 101 containing a positive electrode active material on the surface of a current collector 105 such as an aluminum foil.
The thickness and density of the positive electrode active material layer 101 are not particularly limited because they are appropriately determined according to the intended use of the battery, and can be set according to generally known information.

The positive electrode active material layer 101 contains a positive electrode active material.
The positive electrode active material is not particularly limited, and generally known materials can be used. For example, lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), lithium manganese oxide (LiMn ₂ O ₄ ), solid solution oxide (Li ₂ MnO ₃ —LiMO ₂ (M=Co, Ni, etc.) ), lithium-manganese-nickel oxide (LiNi _1/3 Mn _1/3 Co _1/3 O ₂ ), composite oxides such as olivine-type lithium phosphorous oxide (LiFePO ₄ ); highly conductive oxides such as polyaniline and polypyrrole; Molecules: Li ₂ S, CuS, Li—Cu—S compounds, TiS ₂ , FeS, MoS ₂ , Li—Mo—S compounds, Li—Ti—S compounds, Li—VS compounds, Li—Fe—S compounds sulfide-based positive electrode active materials such as; sulfur-impregnated acetylene black, sulfur-impregnated porous carbon, mixed powder of sulfur and carbon, and other materials using sulfur as an active material; These positive electrode active materials may be used individually by 1 type, and may be used in combination of 2 or more type.
Among these, a sulfide-based positive electrode active material is preferable from the viewpoint of having a higher discharge capacity density and more excellent cycle characteristics, and Li-Mo-S compounds, Li-Ti-S compounds, Li-VS One or two or more selected from compounds are more preferable.

Here, the Li--Mo--S compound contains Li, Mo, and S as constituent elements, and usually an inorganic composition containing molybdenum sulfide and lithium sulfide, which are raw materials, are chemically treated with each other by mechanical treatment. It can be obtained by reacting.
In addition, the Li—Ti—S compound contains Li, Ti, and S as constituent elements, and usually an inorganic composition containing titanium sulfide and lithium sulfide, which are raw materials, is chemically reacted with each other by mechanical treatment. can be obtained by
The Li—V—S compound contains Li, V, and S as constituent elements, and is usually produced by chemically reacting inorganic compositions containing vanadium sulfide and lithium sulfide, which are raw materials, with each other by mechanical treatment. can be obtained by

Although the positive electrode active material layer 101 is not particularly limited, it may contain one or more materials selected from binder resins, thickeners, conductive aids, solid electrolyte materials, etc., as components other than the positive electrode active material. . Each material will be described below.

The positive electrode active material layer 101 may contain a binder resin that serves to bind the positive electrode active materials together and the positive electrode active material and the current collector 105 .
The binder resin according to the present embodiment is not particularly limited as long as it is a normal binder resin that can be used for lithium ion batteries. Butadiene-based rubber, polyimide, and the like can be mentioned. These binders may be used individually by 1 type, and may be used in combination of 2 or more types.

The positive electrode active material layer 101 may contain a thickening agent in order to ensure the fluidity of the slurry suitable for coating. The thickening agent is not particularly limited as long as it is a normal thickening agent that can be used for lithium ion batteries. Examples thereof include water-soluble polymers such as polycarboxylic acid, polyethylene oxide, polyvinylpyrrolidone, polyacrylate, and polyvinyl alcohol. These thickeners may be used singly or in combination of two or more.

The positive electrode active material layer 101 may contain a conductive aid from the viewpoint of improving the conductivity of the positive electrode 110 . The conductive aid is not particularly limited as long as it is a normal conductive aid that can be used in lithium ion batteries, and examples thereof include carbon black such as acetylene black and ketjen black, and carbon materials such as vapor grown carbon fiber. .

The positive electrode according to the present embodiment may contain a solid electrolyte containing the sulfide-based inorganic solid electrolyte material according to the present embodiment described above, or a type different from the sulfide-based inorganic solid electrolyte material according to the present embodiment. A solid electrolyte containing a solid electrolyte material may be included. The type of solid electrolyte material different from the sulfide-based inorganic solid electrolyte material according to the present embodiment is not particularly limited as long as it has ion conductivity and insulation, but is generally used for lithium ion batteries. can be used. Examples include inorganic solid electrolyte materials such as sulfide-based inorganic solid electrolyte materials, oxide-based inorganic solid electrolyte materials, and other lithium-based inorganic solid electrolyte materials; and organic solid electrolyte materials such as polymer electrolytes. More specifically, the inorganic solid electrolyte materials mentioned in the description of the solid electrolyte according to this embodiment can be used.

The mixing ratio of various materials in the positive electrode active material layer 101 is not particularly limited because it is appropriately determined according to the intended use of the battery, and can be set according to generally known information.

(negative electrode)
The negative electrode 130 is not particularly limited, and those commonly used in lithium ion batteries can be used. Although the negative electrode 130 is not particularly limited, it can be manufactured according to a generally known method. For example, it can be obtained by forming a negative electrode active material layer 103 containing a negative electrode active material on the surface of a current collector 105 such as copper.
The thickness and density of the negative electrode active material layer 103 are appropriately determined according to the intended use of the battery and are not particularly limited, and can be set according to generally known information.

The negative electrode active material layer 103 contains a negative electrode active material.
The negative electrode active material is not particularly limited as long as it is a normal negative electrode active material that can be used for the negative electrode of a lithium ion battery. Examples include natural graphite, artificial graphite, resin carbon, carbon fiber, activated carbon, hard carbon, and soft carbon. Carbonaceous materials such as; lithium, lithium alloys, tin, tin alloys, silicon, silicon alloys, gallium, gallium alloys, indium, indium alloys, aluminum, aluminum alloys, etc.; metallic materials such as polyacene, polyacetylene, polypyrrole, etc. conductive polymer; lithium-titanium composite oxide (e.g., Li ₄ Ti ₅ O ₁₂ ), and the like. These negative electrode active materials may be used singly or in combination of two or more.

Although the negative electrode active material layer 103 is not particularly limited, it may contain, as components other than the negative electrode active material, one or more materials selected from, for example, binder resins, thickeners, conductive aids, solid electrolyte materials, and the like. . Although these materials are not particularly limited, for example, the same materials as those used for the positive electrode 110 described above can be used.
The mixing ratio of various materials in the negative electrode active material layer 103 is not particularly limited because it is appropriately determined according to the intended use of the battery, and can be set according to generally known information.

(Electrolyte layer)
Next, the electrolyte layer 120 is described. The electrolyte layer 120 is a layer formed between the positive electrode active material layer 101 and the negative electrode active material layer 103 .
The electrolyte layer 120 includes a separator impregnated with a non-aqueous electrolyte and a solid electrolyte layer containing a solid electrolyte.

The separator according to the present embodiment is not particularly limited as long as it has the function of electrically insulating the positive electrode 110 and the negative electrode 130 and allowing lithium ions to pass through. For example, a porous film can be used.

A microporous polymer film is preferably used as the porous film, and examples of the material include polyolefin, polyimide, polyvinylidene fluoride, polyester, and the like. In particular, porous polyolefin films are preferred, and specific examples include porous polyethylene films and porous polypropylene films.

The non-aqueous electrolytic solution is obtained by dissolving an electrolyte in a solvent.
Any known lithium salt can be used as the electrolyte, and the electrolyte may be selected according to the type of the active material. For example, _LiClO4 , _LiBF6 , _{LiPF6 , LiCF3SO3} , _LiCF3CO2 , _LiAsF6 , _{LiSbF6 , LiB10Cl10} , _{LiAlCl4 ,} LiCl, LiBr, LiB( _C2H5 ) _{4 , CF3} SO ₃ Li, CH ₃ SO ₃ Li, LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , Li(CF ₃ SO ₂ ) ₂ N, lithium lower fatty acid carboxylate, and the like.

The solvent for dissolving the electrolyte is not particularly limited as long as it is commonly used as a liquid for dissolving the electrolyte. Ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC). , diethyl carbonate (DEC), methyl ethyl carbonate (MEC), vinylene carbonate (VC); lactones such as γ-butyrolactone, γ-valerolactone; trimethoxymethane, 1,2-dimethoxyethane, diethyl ether Ethers such as , 2-ethoxyethane, tetrahydrofuran, and 2-methyltetrahydrofuran; sulfoxides such as dimethylsulfoxide; oxolanes such as 1,3-dioxolane and 4-methyl-1,3-dioxolane; acetonitrile, nitromethane, formamide, Nitrogen-containing compounds such as dimethylformamide; organic acid esters such as methyl formate, methyl acetate, ethyl acetate, butyl acetate, methyl propionate, and ethyl propionate; phosphate triesters and diglymes; triglymes; sulfolane, methylsulfolane, etc. sulfolanes; oxazolidinones such as 3-methyl-2-oxazolidinone; sultones such as 1,3-propanesultone, 1,4-butanesultone and naphthsultone; These may be used individually by 1 type, and may be used in combination of 2 or more type.

The solid electrolyte layer according to this embodiment is a layer formed between the positive electrode active material layer 101 and the negative electrode active material layer 103, and is a layer formed of a solid electrolyte containing a solid electrolyte material. The solid electrolyte contained in the solid electrolyte layer is not particularly limited as long as it has lithium ion conductivity. It is preferably an electrolyte.
The content of the solid electrolyte in the solid electrolyte layer according to the present embodiment is not particularly limited as long as the desired insulation is obtained. Above all, it is preferable to be in the range of 50% by volume or more and 100% by volume or less. In particular, in the present embodiment, it is preferable that the solid electrolyte layer is composed only of the solid electrolyte containing the sulfide-based inorganic solid electrolyte material according to the present embodiment.

Moreover, the solid electrolyte layer according to the present embodiment may contain a binder resin. By containing a binder resin, a flexible solid electrolyte layer can be obtained. Examples of the binder resin include fluorine-containing binders such as polytetrafluoroethylene and polyvinylidene fluoride. The thickness of the solid electrolyte layer is, for example, within the range of 0.1 μm or more and 1000 μm or less, and preferably within the range of 0.1 μm or more and 300 μm or less.

Although the embodiments of the present invention have been described above, these are examples of the present invention, and various configurations other than those described above can also be adopted.
It should be noted that the present invention is not limited to the above-described embodiments, and includes modifications, improvements, etc. within the scope of achieving the object of the present invention.

EXAMPLES The present invention will be described below with reference to Examples and Comparative Examples, but the present invention is not limited to these.

[1] Measurement method First, the measurement method in the following examples and comparative examples will be described.

(1) Particle size distribution Particle size distribution of the sulfide-based inorganic solid electrolyte materials obtained in Examples and Comparative Examples by a laser diffraction method using a laser diffraction scattering type particle size distribution analyzer (Malvern, Mastersizer 3000). was measured. From the measurement results, the particle size (D ₅₀ , average particle size) at 50% accumulation in the weight-based cumulative distribution was determined for the sulfide-based inorganic solid electrolyte material.

(2) Measurement of composition ratio The sulfide-based inorganic solid electrolytes obtained in Examples and Comparative Examples were measured by ICP emission spectrometry using an ICP emission spectrometer (manufactured by Seiko Instruments Inc., SPS3000). The mass % of Li, P and S in the material was obtained, and based on this, the molar ratio of each element was calculated.

(3) X-ray diffraction analysis The diffraction spectra of the sulfide-based inorganic solid electrolyte materials obtained in Examples and Comparative Examples were analyzed by X-ray diffraction analysis using an X-ray diffractometer (RINT2000, manufactured by Rigaku Corporation). asked. CuKα rays were used as the radiation source. Here, the maximum diffraction intensity at the diffraction angle 2θ = 35.0 ± 0.1° is defined as the background intensity _IA , and the maximum diffraction peak at the diffraction angle 2θ = 17.2 ± 0.5°. Let _IB be the diffraction intensity, IC be the maximum diffraction intensity of the diffraction peak existing at the diffraction angle 2θ=18.8±0.4°, and _IC be the maximum diffraction intensity at the diffraction angle 2θ=25.6±0.5°. The maximum diffraction intensity of the existing diffraction peak is _ID , the maximum diffraction intensity of the diffraction peak existing at the diffraction angle 2θ = 26.6 ± 0.4 ° is _IE , and the diffraction angle 2θ = 29.2 ± 0. The maximum diffraction intensity of the diffraction peak existing at the position of 0.8° was defined as _IF . Also, I _B /I _A and I _C / _IA were determined respectively.

(4) Measurement of Lithium Ion Conductivity The sulfide-based inorganic solid electrolyte materials obtained in Examples and Comparative Examples were measured for lithium ion conductivity by an AC impedance method. Further, after exposing 1.0 g of the sulfide-based inorganic solid electrolyte materials obtained in Examples and Comparative Examples to the atmosphere at 25°C for 10 minutes, the lithium ion conductivity of the sulfide-based inorganic solid electrolyte materials was measured. were performed respectively.
Potentiostat/galvanostat SP-300 manufactured by Biologic was used to measure the lithium ion conductivity. The size of the sample was 9.5 mm in diameter and 1.2 to 2.0 mm in thickness. The measurement conditions were an applied voltage of 10 mV, a measurement temperature of 27.0°C, a measurement frequency range of 0.1 Hz to 7 MHz, and a Li foil electrode. .
Here, the sample for lithium ion conductivity measurement is obtained by pressing 150 mg of the powdery sulfide-based inorganic solid electrolyte material obtained in Examples and Comparative Examples at 270 MPa for 10 minutes using a pressing device. A plate-like sulfide-based inorganic solid electrolyte material having a diameter of 9.5 mm and a thickness of 1.2 to 2.0 mm was used.

(5) Measurement of Maximum Value of Oxidative Decomposition Current Using a pressing device, 120 to 150 mg of the powdery sulfide-based inorganic solid electrolyte materials obtained in Examples and Comparative Examples were pressed at 270 MPa for 10 minutes to obtain a diameter of 9.5 mm. A plate-like sulfide-based inorganic solid electrolyte material (pellet) having a size of 5 mm and a thickness of 1.3 mm was obtained. Next, Li foils as reference and counter electrodes were press-bonded to one surface of the obtained pellet under conditions of 18 MPa for 10 minutes, and SUS314 foil was adhered to the other surface as a working electrode.
Next, using a Potentiostat/Galvanostat SP-300 manufactured by Biologic Inc., the sulfide-based inorganic solid electrolyte material is oxidatively decomposed under conditions of a temperature of 25° C., a sweep voltage range of 0 to 5 V, and a voltage sweep rate of 5 mV/sec. The maximum current value was obtained and evaluated according to the following criteria.
◎: 0.03 μA or less ○: 0.03 μA or less 0.50 μA or less ×: 0.50 μA or less

[2] Production of solid electrolyte material <Example 1>
A sulfide-based inorganic solid electrolyte material was produced by the following procedure.
Li ₂ S (manufactured by Furukawa Co., Ltd., purity 99.9%), P ₂ S ₅ (manufactured by Kanto Chemical Co., Ltd.) and Li ₃ N (manufactured by Furukawa Co., Ltd.) were used as raw materials.
First, a rotary blade pulverizer and an alumina pot (with an internal volume of 400 mL) were placed in the glove box, and then high-purity dry argon gas (H ₂ O<1 ppm, O ₂ <1 ppm) injection and vacuum degassing were performed three times.
Then, in a glove box, using a rotary blade pulverizer (rotation speed 18000 rpm), Li ₂ S powder, P ₂ S ₅ powder, and Li ₃ N powder (Li ₂ S: P ₂ S ₅ : Li ₃ N = 71.1: 23.7: 5.3 (mol%)) by mixing a total of 5 g (mixing for 10 seconds and standing for 10 seconds 10 times (cumulative mixing time: 100 seconds)), A raw inorganic composition was prepared.
Here, the Li ₂ S powder, the P ₂ S ₅ powder and the Li ₃ N powder were charged into the rotary blade pulverizer in the glove box according to the following procedure. First, Li ₂ S powder, P ₂ S ₅ powder and Li ₃ N powder were put into the side box of the glove box with the door inside the main body of the glove box closed. Next, high-purity dry argon gas introduced from the glove box was injected into the side box and vacuum deaeration was performed three times. Next, the door inside the main body of the glove box was opened, the Li ₂ S powder, the P ₂ S ₅ powder and the Li ₃ N powder were put into the rotating blade type pulverizer inside the main body of the glove box, and the pulverizer was closed.

Subsequently, the starting inorganic composition and 500 g of ZrO ₂ balls with a diameter of 10 mm were put into an alumina pot (inner volume: 400 mL) in the glove box, and the pot was sealed. Here, an O-ring (standard P-75) was used as the packing for the cover of the pot made of alumina. Also, dry argon gas was circulated in the glove box to adjust the moisture concentration to 0.5 ppm and the oxygen concentration to 0.6 ppm.
Next, remove the alumina pot from the glove box, attach the alumina pot to a ball mill installed in an atmosphere of dry air introduced through a membrane air dryer, mix at 120 rpm for 500 hours, and mix the raw material inorganic composition. I vitrified things. At this time, the dry air obtained through the membrane air dryer had a moisture concentration of 600 ppm. Every 48 hours of mixing, the powder attached to the inner wall of the pot was scraped off in the glove box, and after sealing, milling was continued in a dry air atmosphere.
Next, an alumina pot was placed in the glove box, the obtained powder was transferred from the alumina pot to a carbon crucible, and heat-treated at 270° C. for 2 hours in a heating furnace installed in the glove box.
Each evaluation was performed on the obtained sulfide-based inorganic solid electrolyte material. Table 1 shows the results obtained.

<Example 2>
_The mixing ratio _{of Li2S} powder, _P2S5 powder and _Li3N powder was changed to _Li2S : _P2S5 : _Li3N =67.5:22.5:10.0 (mol%). A sulfide-based inorganic solid electrolyte material was produced in the same manner as in Example 1 except for the above, and each evaluation was performed. The obtained results are shown in Table 1, respectively.

<Example 3>
The mixing ratio _{of Li2S} powder, _P2S5 powder and _Li3N powder was changed to _Li2S : _P2S5 : _Li3N =65.9:22.0:12.2 (mol% ₎ . A sulfide-based inorganic solid electrolyte material was produced in the same manner as in Example 1 except for the above, and each evaluation was performed. The obtained results are shown in Table 1, respectively.

<Example 4>
Li ₂ S (manufactured by Furukawa Co., Ltd., purity 99.9%) and P ₂ S ₅ (reagent manufactured by Kanto Kagaku) were used as raw materials. P ₄ S ₃ was produced by the following procedure.
First, in an argon glove box, stoichiometric amounts of sulfur (Kanto Chemical reagent 99.5%) and red phosphorus (Wako Pure Chemical reagent 98%) were placed in a quartz distillation apparatus and slowly heated to 180°C. After warming, the mixture was reacted with sufficient stirring. After holding at 320° C. for 1 hour, the temperature was raised to 420° C. to recover P ₄ S ₃ as a distillate. The P ₄ S ₃ taken out was pulverized in an agate mortar and then sieved with a stainless steel sieve to recover powders of 75 μm or less and used as raw materials for solid electrolyte materials.
Subsequently, the mixing ratio of Li ₂ S powder, P ₂ S ₅ powder and P ₄ S ₃ powder was Li ₂ S:P ₂ S ₅ :P ₄ S ₃ =77.8:21.1:1.1 (mol %), a sulfide solid electrolyte material was produced in the same manner as in Example 1, and each evaluation was performed. The obtained results are shown in Table 1, respectively.

<Comparative Example 1>
_The mixing ratio _{of Li2S} powder, _P2S5 powder and _Li3N powder was changed to _Li2S : _P2S5 : _Li3N =72.6:24.2:3.2 (mol%). A sulfide-based inorganic solid electrolyte material was produced in the same manner as in Example 1 except for the above, and each evaluation was performed. The obtained results are shown in Table 1, respectively.

<Comparative Example 2>
_The mixing ratio _{of Li2S} powder, _P2S5 powder and _Li3N powder was changed to _Li2S : _P2S5 : _Li3N =73.8:24.6:1.6 (mol%). A sulfide-based inorganic solid electrolyte material was produced in the same manner as in Example 1 except for the above, and each evaluation was performed. The obtained results are shown in Table 1, respectively.

<Comparative Example 3>
A sulfide-based inorganic solid electrolyte material was produced in the same manner as in Example 1, except that the water concentration in the glove box was adjusted to 4000 ppm, and each evaluation was performed. The obtained results are shown in Table 1, respectively.

<Comparative Example 4>
A sulfide-based inorganic solid electrolyte material was produced in the same manner as in Example 2, except that the water concentration in the glove box was adjusted to 4000 ppm, and each evaluation was performed. The obtained results are shown in Table 1, respectively.

<Comparative Example 5>
A sulfide-based inorganic solid electrolyte material was produced in the same manner as in Example 3, except that the water concentration in the glove box was adjusted to 4000 ppm, and each evaluation was performed. The obtained results are shown in Table 1, respectively.

<Comparative Example 6>
A sulfide-based inorganic solid electrolyte material was produced in the same manner as in Example 4, except that the water concentration in the glove box was adjusted to 4000 ppm, and each evaluation was performed. The obtained results are shown in Table 1, respectively.

The sulfide-based inorganic solid electrolyte material of the example was more suppressed in deterioration of lithium ion conductivity than the sulfide-based inorganic solid electrolyte material of the comparative example even when exposed to the air. That is, it can be understood that the sulfide-based inorganic solid electrolyte materials of the examples can suppress a decrease in lithium ion conductivity when exposed to the air.
Here, the X-ray diffraction spectra of the sulfide-based inorganic solid electrolyte materials obtained in Examples and Comparative Examples are shown in FIGS. 2 and 3, respectively.

100 Lithium ion battery 101 Positive electrode active material layer 103 Negative electrode active material layer 105 Current collector 110 Positive electrode 120 Electrolyte layer 130 Negative electrode

Claims (18)

A sulfide-based inorganic solid electrolyte material having lithium ion conductivity,
In the spectrum obtained by X-ray diffraction using CuKα rays as a radiation source, diffraction peaks are observed at diffraction angles 2θ = 17.2 ± 0.5° and 2θ = 18.8 ± 0.4°. have
Let I _B be the maximum diffraction intensity of the diffraction peak existing at the diffraction angle 2θ = 17.2 ± 0.5 °,
A sulfide-based inorganic solid electrolyte having a value of _IC / _IB of 0.50 or more, where IC _is the maximum diffraction intensity of a diffraction peak present at a diffraction angle of 2θ = 18.8 ± 0.4°. material. In the sulfide-based inorganic solid electrolyte material according to claim 1,
In the spectrum obtained by X-ray diffraction using CuKα rays as a radiation source, the maximum diffraction intensity at the diffraction angle 2θ=35.0±0.1° is defined as intensity _IA , and the diffraction angle 2θ=17.2±0. A sulfide-based inorganic solid electrolyte material having a value of _IB / _IA of 2.0 or more, where _IB is the maximum diffraction intensity of a diffraction peak present at a position of 5°. In the sulfide-based inorganic solid electrolyte material according to claim 1 or 2,
In the spectrum obtained by X-ray diffraction using CuKα rays as the radiation source, the maximum diffraction intensity at the diffraction angle 2θ=35.0±0.1° is defined as the intensity _IA , and the diffraction angle 2θ=18.8±0. A sulfide-based inorganic solid _{electrolyte material having a value of IC/IA of 2.0} or more, where IC is the maximum diffraction intensity of a diffraction peak present at a position of 4°. In the 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 radiation as a radiation source, the position of the diffraction angle 2θ=25.6±0.5°, the diffraction angle 2θ=26.6±0.4° and the diffraction angle 2θ=29. A sulfide-based inorganic solid electrolyte material further having diffraction peaks at positions of 2±0.8°. A sulfide-based inorganic solid electrolyte material having lithium ion conductivity,
After the sulfide-based inorganic solid electrolyte material was heat-treated at 270° C. for 2 hours, X-ray diffraction measurement was performed using CuKα rays as a radiation source. = 17.2 ± 0.5° and diffraction angle 2θ = 18.8 ± 0.4°,
Let I _B be the maximum diffraction intensity of the diffraction peak existing at the diffraction angle 2θ = 17.2 ± 0.5 °,
A sulfide-based inorganic solid electrolyte having a value of _IC / _IB of 0.50 or more, where IC _is the maximum diffraction intensity of a diffraction peak present at a diffraction angle of 2θ = 18.8 ± 0.4°. material. In the sulfide-based inorganic solid electrolyte material according to claim 5,
After the sulfide-based inorganic solid electrolyte material was heat-treated at 270° C. for 2 hours, X-ray diffraction measurement was performed using CuKα rays as a radiation source. =35.0±0.1°, and the maximum diffraction intensity of the diffraction peak at the diffraction angle 2θ=17.2±0.5° is _{IB .} , a sulfide-based inorganic solid electrolyte material having a value of I _B / _IA of 2.0 or more. In the sulfide-based inorganic solid electrolyte material according to claim 5 or 6,
After the sulfide-based inorganic solid electrolyte material was heat-treated at 270° C. for 2 hours, X-ray diffraction measurement was performed using CuKα rays as a radiation source. =35.0±0.1°, and the maximum diffraction intensity of the diffraction peak at the diffraction angle 2θ=18.8±0.4° is _{IC .} , a sulfide-based inorganic solid electrolyte material having an _IC / _IA value of 2.0 or more. In the sulfide-based inorganic solid electrolyte material according to any one of claims 5 to 7,
After the sulfide-based inorganic solid electrolyte material was heat-treated at 270° C. for 2 hours, X-ray diffraction measurement was performed using CuKα rays as a radiation source. = 25.6 ± 0.5°, diffraction angles 2θ = 26.6 ± 0.4°, and diffraction angles 2θ = 29.2 ± 0.8°, respectively. Solid electrolyte material. In the sulfide-based inorganic solid electrolyte material according to any one of claims 1 to 8,
A sulfide-based inorganic solid electrolyte material containing Li, P and S as constituent elements. In the sulfide-based inorganic solid electrolyte material according to claim 9,
The molar ratio Li/P of the Li content to the P content in the sulfide-based inorganic solid electrolyte material is 1.0 or more and 5.0 or less, and the S content to the P content A sulfide-based inorganic solid electrolyte material having a molar ratio S/P of 2.0 or more and 6.0 or less. In the sulfide-based inorganic solid electrolyte material according to any one of claims 1 to 10,
The shape of the sulfide-based inorganic solid electrolyte material is particulate,
A sulfide-based inorganic solid electrolyte material having an average particle diameter _d50 of 1 µm or more and 100 µm or less in a weight-based particle size distribution measured by a laser diffraction scattering particle size distribution measurement method. In the sulfide-based inorganic solid electrolyte material according to any one of claims 1 to 11,
A sulfide-based inorganic solid electrolyte material used in lithium-ion batteries. A solid electrolyte comprising the sulfide-based inorganic solid electrolyte material according to any one of claims 1 to 12. A solid electrolyte membrane comprising the solid electrolyte according to claim 13 as a main component. In the solid electrolyte membrane according to claim 14,
A solid electrolyte membrane, which is a pressure-molded body of the particulate solid electrolyte. In the solid electrolyte membrane according to claim 14 or 15,
A solid electrolyte membrane, wherein the content of the binder resin in the solid electrolyte membrane is less than 0.5% by mass when the solid electrolyte membrane as a whole is 100% by mass. In the solid electrolyte membrane according to any one of claims 14 to 16,
A solid electrolyte membrane, wherein the content of the sulfide-based inorganic solid electrolyte material in the solid electrolyte membrane is 50% by mass or more when the entire solid electrolyte membrane is 100% by mass. A lithium ion battery comprising a positive electrode including a positive electrode active material layer, an electrolyte layer, and a negative electrode including a negative electrode active material layer,
A lithium ion battery in which at least one of the positive electrode active material layer, the electrolyte layer and the negative electrode active material layer comprises the sulfide-based inorganic solid electrolyte material according to any one of claims 1 to 12.

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