Inorganic solid electrolyte materials, solid electrolytes, solid electrolyte membranes and lithium-ion batteries

Abstract

An inorganic solid electrolyte material, which contains sulfide-based inorganic solid electrolyte particles. In the frequency distribution of the circularity of the particles plotted with the circularity of the particles in the material as the horizontal axis and the frequency on a number basis as the vertical axis, the 10% cumulative value D 10 is 0.54 to 0.80. Further, the median particle size d 50 in the material is 0.1 to 10 μm.

Description

Technical Field

[0001] The present invention relates to an inorganic solid electrolyte material, a solid electrolyte, a solid electrolyte film, and a lithium ion battery. Background Art

[0002] Generally, lithium ion batteries are used as power sources for small portable devices such as mobile phones and laptop computers. In addition, recently, in addition to small portable devices, lithium ion batteries have also begun to be used as power sources for electric vehicles, power storage, etc.

[0003] Currently, commercially available lithium ion batteries use electrolytes containing flammable organic solvents.

[0004] On the other hand, research is being conducted on lithium ion batteries (hereinafter, also referred to as all-solid-state lithium ion batteries) in which the electrolyte is changed to a solid electrolyte and the battery is made all-solid-state. Since all-solid-state lithium ion batteries do not contain flammable organic solvents inside the battery, it is considered that the safety device is simplified and the manufacturing cost and productivity are excellent.

[0005] As a solid electrolyte material used in solid electrolytes, for example, inorganic solid electrolyte materials are known.

[0006] As an example of the prior art of solid electrolyte materials, the technique described in Patent Document 1 can be cited. Patent Document 1 describes sulfide-based inorganic solid electrolyte particles that satisfy all of the following elements A.

[0007] <Element A>

[0008] Let the perimeter of the projected particle of the inorganic solid electrolyte particle be L.

[0009] Let the cross-sectional area of the projected particle of the inorganic solid electrolyte particle be A.

[0010] The concavo-convex coefficient FU is represented by the following formula (1) and is in the range of 0.85 or more and 1 or less.

[0011] FU = 4πA / L 2 (1)

[0012] Prior Art Documents

[0013] Patent Documents

[0014] Patent Document 1: Japanese Patent No. 6691481. Summary of the Invention

[0015] Problems to be Solved by the Invention

[0016] One of the performances required for solid electrolyte materials is high ionic conductivity.

[0017] Based on the findings of the present inventors, for sulfide-based inorganic solid electrolyte particles as described in Patent Document 1, there is room for improvement in ionic conductivity.

[0018] The present invention has been completed in view of the above circumstances. One object of the present invention is to provide sulfide-based inorganic solid electrolyte particles having high ionic conductivity.

[0019] Means for Solving the Problem

[0020] The present inventors have completed the invention provided below and solved the above problems.

[0021] According to the present invention, there is provided an inorganic solid electrolyte material which is an inorganic solid electrolyte material containing sulfide-based inorganic solid electrolyte particles, and in the frequency distribution of the circularity of the particles with the circularity of the particles in the material as the horizontal axis and the frequency on a number basis as the vertical axis, the 10% cumulative value D 10 is 0.54 to 0.80, and the median particle diameter d 50 in the material is 0.1 to 10 μm.

[0022] Further, according to the present invention, there is provided a solid electrolyte containing the above inorganic solid electrolyte material.

[0023] Further, according to the present invention, there is provided a solid electrolyte membrane containing the above solid electrolyte as a main component.

[0024] Further, according to the present invention, there is provided a lithium ion battery which is a lithium ion battery having a positive electrode including a positive electrode active material layer, an electrolyte layer, and a negative electrode including a negative electrode active material layer, wherein at least one of the positive electrode active material layer, the electrolyte layer, and the negative electrode active material layer contains the above inorganic solid electrolyte material.

[0025] Effects of the Invention

[0026] According to the present invention, there are provided sulfide-based inorganic solid electrolyte particles having high ionic conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a supplementary diagram for intuitively understanding the concept of "circularity".

[0028] Figure 2 is a cross-sectional view showing an example of the structure of a lithium ion battery. DETAILED DESCRIPTION OF THE INVENTION

[0029] Hereinafter, embodiments of the present invention will be described while referring to the Figure 1 accompanying drawings.

[0030] All the attached drawings are for illustration purposes only. The shapes, dimensional ratios, etc. shown in the drawings do not necessarily correspond to the actual articles.

[0031] In this specification, unless otherwise specified, the expression "X to Y" in the description of a numerical range means X or more and Y or less. For example, "1 to 5 mass%" means "1 mass% or more and 5 mass% or less".

[0032] The expression "(meth)acrylic acid" in this specification represents a concept including both acrylic acid and methacrylic acid. The same applies to similar expressions such as "(meth)acrylate".

[0033] Hereinafter, the sulfide-based inorganic solid electrolyte particles may sometimes be simply referred to as "particles".

[0034] <Inorganic solid electrolyte material>

[0035] The inorganic solid electrolyte material of this embodiment includes sulfide-based inorganic solid electrolyte particles.

[0036] In the frequency distribution of the circularity of the particles plotted with the circularity of the sulfide-based inorganic solid electrolyte particles in the material as the horizontal axis and the frequency on a number basis as the vertical axis, the 10% cumulative value D 10 is 0.54 to 0.80.

[0037] In addition, the median particle size d of the sulfide-based inorganic solid electrolyte particles in the material 50 is 0.1 to 10 μm.

[0038] "Circularity" is an index indicating the deformation / deformation from a perfect circle of a certain figure.

[0039] When the area of the figure is set as S, the perimeter is set as L, and the pi is set as π, the circularity is represented by 4πS / L 2 and is expressed.

[0040] When the figure is a shape close to a perfect circle, the circularity is close to 1. When the shape of the figure is complex, the circularity is far from 1 and is a smaller value.

[0041] Figure 1 is a supplementary figure for intuitively understanding the concept of circularity. Figure 1 The circularity of the figure in (A) is about 1. Figure 1 The circularity of the figure in (B) is about 0.7. Figure 1 The circularity of the figure in (C) is about 0.25. From this, it can be understood that the closer the value of the circularity of the figure is to 1, the closer the figure has a contour close to a perfect circle, and the smaller the circularity of the figure, the more the figure has a contour curved from a perfect circle.

[0042] The present inventors have studied the improvement of inorganic solid electrolyte materials from various viewpoints. Through research, the present inventors believe that certain indices related to the shape of sulfide-based inorganic solid electrolyte particles may be related to the ionic conductivity.

[0043] Based on this finding, the present inventors further conducted research. Specifically, as "certain indices related to the shape of sulfide-based inorganic solid electrolyte particles", the circularity, which is an index representing the deformation / deformation from a perfect circle, was studied. In addition, since the inorganic solid electrolyte material is an "aggregate" of a plurality of sulfide-based inorganic solid electrolyte particles, by appropriately designing the "distribution" of the circularity of the particles, the ionic conductivity may be improved.

[0044] Based on the above considerations, the present inventors further conducted research. Moreover, the present inventors found that in an inorganic solid electrolyte material containing sulfide-based inorganic solid electrolyte particles, in the frequency distribution of the circularity of the particles plotted with the circularity of the sulfide-based inorganic solid electrolyte particles as the horizontal axis and the frequency on a number basis as the vertical axis, by designing the material so that the 10% cumulative value D 10 is 0.54 to 0.80, the ionic conductivity can be improved.

[0045] Regarding the improvement of the ionic conductivity by D 10 being 0.54 to 0.80, it can be explained as follows.

[0046] D 10 being 0.54 or more means that there are few particles with extreme deformation in the group of particles. It is considered that by having few particles with extreme deformation, the "gap" between the particles is reduced, and the ionic conductivity is improved.

[0047] In addition, D 10 being 0.80 or less means that there are not too many particles close to a perfect circle, and the group of particles contains "generally deformed" particles in a certain proportion. It is considered that when the shape of the particles is too close to a perfect circle, the contact between the particles may become "point-like", resulting in a decrease in the ionic conductivity. Therefore, it is considered that D 10 is preferably 0.80 or less.

[0048] In addition to this, in the present embodiment, the median particle size d 50 of the particles on a number basis is 0.1 to 10 μm. This means that the particles are "neither too large nor too small". It is speculated that since the particles are not too large, the "gap" between the particles is reduced, resulting in an increase in the ionic conductivity. In addition, it is speculated that since the particles are not too small, the contact surface between the particles is reduced, resulting in an increase in the ionic conductivity.

[0049] In addition, it is considered that the "concavo-convex coefficient" described in Patent Document 1 is equivalent to circularity. However, in Patent Document 1, there is no mention of the "distribution" of the circularity of electrolyte particles, let alone D 10 . Focusing on the frequency distribution of the circularity of electrolyte particles, the concept of designing electrolyte particles such that D 10 is 0.54 to 0.80, and the concept of further optimizing the diameter of electrolyte particles based on circularity is unique to the present inventors.

[0050] Preferably, an appropriate material is used and appropriate manufacturing conditions are selected to manufacture the inorganic solid electrolyte material of the present embodiment (D 10 is 0.54 to 0.80). To manufacture the inorganic solid electrolyte material of the present embodiment, for example, it is preferable to (i) perform ball milling treatment under appropriate conditions to change the shape of the particles of the inorganic solid electrolyte material in a glass state and / or (ii) perform an appropriate sieving operation. When an appropriate manufacturing method / manufacturing conditions are not selected, the inorganic solid electrolyte material of the present embodiment may sometimes not be obtained.

[0051] A more specific manufacturing method of the inorganic solid electrolyte material of the present embodiment will be described later.

[0052] Continue the description related to the inorganic solid electrolyte material of the present embodiment.

[0053] (Regarding the frequency distribution of sulfide-based inorganic solid electrolyte particles)

[0054] As described above, as long as D 10 is 0.54 to 0.80, from the viewpoint of further increasing the ionic conductivity, D 10 is more preferably 0.60 to 0.75.

[0055] In the present embodiment, in addition to D 10 , by setting the 50% cumulative value D 50 in the frequency distribution of the circularity of the particles to an appropriate value, the ionic conductivity can sometimes be further increased. Specifically, D 50 is preferably less than 0.85, more preferably 0.70 to 0.84, and further preferably 0.75 to 0.82.

[0056] It is considered that D 50 less than 0.85 is similar to D 10 being 0.80 or less, indicating that particles with deformation are included to a certain extent in the group of particles. That is, it is considered that by D 50 being less than 0.85, it is easier for the particles to contact with each other with a larger area, and the ionic conductivity is further improved.

[0057] On the other hand, it is considered that by D50 is 0.70 or more, the gaps between particles become fewer, and the ionic conductivity can be further increased.

[0058] In addition, in the present embodiment, sometimes by setting the 90% cumulative value D in the frequency distribution of the circularity of the particles 90 to an appropriate value, the ionic conductivity can also be further increased. Specifically, D 90 is preferably 0.95 or less, more preferably 0.85 to 0.95, and still more preferably 0.87 to 0.92.

[0059] It is considered that D 90 being 0.95 or less also indicates that the group of particles contains deformed particles to a certain extent. That is, when D 90 is 0.95 or less, it is easier for the particles to contact with a larger area, and the ionic conductivity is further improved.

[0060] On the other hand, it is considered that when D 90 is 0.85 or more, the gaps between particles become fewer, and the ionic conductivity can be further increased.

[0061] In the present embodiment, sometimes by appropriately designing the value of (D 90 - D 10 ) / D 50 , the ionic conductivity can be further increased. Specifically, (D 90 - D 10 ) / D 50 is preferably 0.10 to 0.45, more preferably 0.20 to 0.45.

[0062] (D 90 - D 10 ) / D 50 The index represents the broadness / sharpness of the frequency distribution. The smaller this value, the sharper the frequency distribution, which means that the particles are relatively homogeneous on the scale of circularity, and there are fewer particles with extremely large or extremely small circularity. In addition, the larger this value, the wider the frequency distribution, which means that the proportion of particles with circularity deviating from the average in the group of particles (particles with larger circularity or smaller circularity) is larger.

[0063] It is considered that (D 90 - D 10 ) / D 50 being 0.10 or more, that is, the frequency distribution is moderately wide, and the group of particles contains particles with circularity deviating from the average to a certain proportion. As a result, as a whole group of particles, the gaps between particles become fewer, the contact area becomes larger, and the ionic conductivity is further improved.

[0064] In addition, it is considered that (D 90 - D10 ) / D 50 is 0.45 or less, that is, the frequency distribution is moderately sharp, and there are few particles with extremely large or small circularity, so it is difficult to form gaps between particles that may reduce the ionic conductivity, and the ionic conductivity is further improved.

[0065] The frequency distribution of the circularity of the particles can be obtained, for example, by the steps of (1) photographing the particles with an electron microscope, (2) calculating the circularity of each particle based on the area and perimeter of each particle in the photographed image, and (3) plotting with the circularity of each particle as the horizontal axis and the frequency on a number basis as the vertical axis. For examples of specific calculation methods, refer to the description in the examples.

[0066] (Regarding the constituent elements and their composition)

[0067] From the viewpoints of electrochemical stability, stability in moisture or air, operability, etc., it is preferable that the inorganic solid electrolyte material of the present embodiment contains Li, P, and S as constituent elements.

[0068] In addition, for the inorganic solid electrolyte material of the present embodiment, from the viewpoints of further improving lithium ion conductivity, electrochemical stability, stability in moisture or air, and operability, etc., the molar ratio Li / P of the content of the above-mentioned Li to the content of the above-mentioned 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 4.0 or less, further preferably 2.5 or more and 3.8 or less, still more preferably 2.8 or more and 3.6 or less, still more preferably 3.0 or more and 3.5 or less, still more preferably 3.1 or more and 3.4 or less, and particularly preferably 3.1 or more and 3.3 or less.

[0069] In addition, the molar ratio S / P of the content of the above-mentioned S to the content of the above-mentioned P is preferably 2.0 or more and 6.0 or less, more preferably 3.0 or more and 5.0 or less, further preferably 3.5 or more and 4.5 or less, still more preferably 3.8 or more and 4.2 or less, still more preferably 3.9 or more and 4.1 or less, and particularly preferably 4.0.

[0070] The contents of Li, P, and S in the inorganic solid electrolyte material can be determined, for example, by ICP emission spectrometry and X-ray analysis.

[0071] (Regarding the particle size distribution)

[0072] In the present embodiment, in addition to the distribution of the circularity of the particles, by appropriately designing the particle size distribution, the ionic conductivity can be further improved.

[0073] As described above, in the present embodiment, the median particle size d on a number basis 50is from 0.1 to 10 μm, preferably from 0.1 to 6.0 μm. It is considered that through d 50 being appropriately large, the contact surface (interface) between particles is reduced, and better ionic conductivity can be obtained. In addition, it is considered that through d 50 not being too large, it is difficult for gaps to be generated between particles, and better ionic conductivity can be obtained.

[0074] In addition, sometimes by appropriately designing the 10% cumulative value d 10 under the particle number standard, the ionic conductivity can be further improved. d 10 is preferably from 0.05 to 5.0 μm, more preferably from 0.5 to 3.0 μm. d 10 Being appropriately large means that there are few overly fine particles. It is considered that with few overly fine particles, the contact surface (interface) between particles is reduced, and better ionic conductivity can be obtained. In addition, through d 10 not being too large, it is difficult for gaps to form between particles, and better ionic conductivity can be obtained.

[0075] Furthermore, sometimes by appropriately designing the 90% cumulative value d 90 under the particle number standard, the ionic conductivity can also be further improved. d 90 is preferably from 2.0 to 20.0 μm, more preferably from 2.0 to 10.0 μm. It is considered that through d 90 not being too large, it is difficult for gaps to form between particles, and better ionic conductivity can be obtained. In addition, it is considered that through d 90 being appropriately large, the contact surface (interface) between particles is reduced, and better ionic conductivity can be obtained.

[0076] From the perspective other than ionic conductivity, by d 90 not being too large, the advantage of being able to easily reduce the thickness of the solid electrolyte membrane can also be obtained.

[0077] For example, the particle size distribution under the number standard (as the data for the calculation of d 10 , d 50 and d 90 ) can be obtained through the steps of (1) photographing the particles with an electron microscope, (2) measuring the fixed-direction tangent diameter (Feret diameter) of each particle in the photographed image, and (3) plotting with the fixed-direction tangent diameter (Feret diameter) of each particle as the horizontal axis and the frequency under the number standard as the vertical axis. For examples of specific calculation methods, please refer to the description in the examples.

[0078] (Other matters)

[0079] Generally, the inorganic solid electrolyte material of the present embodiment has excellent electrochemical stability. Electrochemical stability refers to the property of being difficult to oxidize and reduce, for example, in a wide voltage range. More specifically, in the inorganic solid electrolyte material of the present embodiment, the maximum value of the oxidation decomposition current of the inorganic solid electrolyte material measured under the conditions of a temperature of 25 °C, a scanning voltage range of 0 to 5 V, and a voltage scanning speed of 5 mV / second is preferably 0.50 μA or less, more preferably 0.20 μA or less, further preferably 0.10 μA or less, still more preferably 0.05 μA or less, and particularly preferably 0.03 μA or less.

[0080] When the maximum value of the oxidation decomposition current of the inorganic solid electrolyte material is below the above upper limit value, the oxidation decomposition of the inorganic solid electrolyte material in the lithium-ion battery can be suppressed, which is therefore preferred.

[0081] There is no particular limitation on the lower limit value of the maximum value of the oxidation decomposition current of the inorganic solid electrolyte material, and it is, for example, 0.0001 μA or more.

[0082] The inorganic solid electrolyte material of the present embodiment can be used for any application that requires lithium-ion conductivity. Among them, the inorganic solid electrolyte material of the present 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. Further, the inorganic solid electrolyte material of the present embodiment is suitable for constituting the positive electrode active material layer, negative electrode active material layer, solid electrolyte layer, etc. of all-solid-state lithium-ion batteries, and is particularly suitable for constituting the solid electrolyte layer of all-solid-state lithium-ion batteries.

[0083] As an example of an all-solid-state lithium-ion battery using the inorganic solid electrolyte material of the present embodiment, a battery in which a positive electrode, a solid electrolyte layer, and a negative electrode are laminated in this order can be cited.

[0084] (Manufacturing method of inorganic solid electrolyte material)

[0085] Preferably, the inorganic solid electrolyte material of the present embodiment can be obtained by a manufacturing method including the following steps (A), (B1), (B2), and (C).

[0086] In addition, as needed, the manufacturing method of the inorganic solid electrolyte material of the present embodiment preferably further includes the following step (D). In this case, step (C) can be carried out before step (D), after step (D), or both.

[0087] Step (A): A step of preparing a raw material composition of an inorganic solid electrolyte material containing lithium sulfide and phosphorus sulfide.

[0088] Step (B1): A step of obtaining a vitrified inorganic solid electrolyte material in a glass state by subjecting a raw material composition of an inorganic solid electrolyte material to mechanical treatment, thereby causing a chemical reaction between lithium sulfide and phosphorus sulfide as raw materials while vitrifying.

[0089] Step (B2): A step of pulverizing and refining the obtained inorganic solid electrolyte material in a glass state.

[0090] Step (C): A step of classifying the obtained inorganic solid electrolyte material.

[0091] Step (D): A step of heating (annealing) the obtained inorganic solid electrolyte material in a glass state to crystallize at least a part thereof.

[0092] In the present embodiment, by appropriately performing step (B2) and / or (C), it is easy to manufacture an inorganic solid electrolyte material having D 10 ranging from 0.54 to 0.80 and d 50 ranging from 0.1 to 10 μm. In particular, in the present embodiment, it is preferable to perform both step (B2) and (C).

[0093] Hereinafter, each step will be specifically described.

[0094] Step (A) of preparing a raw material composition

[0095] First, a raw material composition of an inorganic solid electrolyte material containing lithium sulfide and phosphorus sulfide as raw materials in a specific ratio is prepared. Here, the mixing ratio of each raw material in the raw material composition is adjusted so that the obtained inorganic solid electrolyte material has a desired composition ratio.

[0096] The raw material composition of the inorganic solid electrolyte material may further contain lithium nitride.

[0097] As a method of mixing the respective raw materials, there is no particular limitation as long as it is a mixing method capable of uniformly mixing the respective raw materials. For example, a ball mill, a bead mill, a vibration mill, a hammer mill, a mixer (such as a pugmixer, a ribbon mixer, a drum mixer, a tumbler mixer, a V-type mixer, etc.), a kneader, a twin-screw kneader, a jet mill, etc. can be used for mixing. As long as it is at the laboratory level, mixing using a mortar such as agate or alumina is also possible.

[0098] Mixing conditions such as the stirring speed, treatment time, temperature, reaction pressure, and gravitational acceleration applied to the mixture when mixing the respective raw materials can be appropriately determined according to the processing amount of the mixture.

[0099] There is no particular limitation on the lithium sulfide used as a raw material, and commercially available lithium sulfide can be used. For example, lithium sulfide obtained by the reaction of lithium hydroxide and hydrogen sulfide can also be used. From the viewpoints of obtaining a high-purity inorganic solid electrolyte material and suppressing side reactions, lithium sulfide with few impurities is preferably used.

[0100] In the present embodiment, the lithium sulfide also includes polysulfide. As the lithium sulfide, Li2S is preferred.

[0101] There is no particular limitation on the phosphorus sulfide used as a raw material. Commercially available phosphorus sulfides (such as P2S5, P4S3, P4S7, P4S5, etc.) can be used. From the viewpoints of obtaining a high-purity inorganic solid electrolyte material and suppressing side reactions, phosphorus sulfide with few impurities is preferably used. As the phosphorus sulfide, P2S5 is preferred. In addition, monomeric phosphorus (P) and monomeric sulfur (S) in a corresponding molar ratio can also be used instead of phosphorus sulfide. As long as the monomeric phosphorus (P) and monomeric sulfur (S) are industrially produced and sold substances, they can be used without particular limitation.

[0102] As a raw material, lithium nitride can be used. Here, since nitrogen in lithium nitride is discharged into the system in the form of N2, by using lithium nitride as a raw material, that is, an inorganic compound, for an inorganic solid electrolyte material including Li, P, and S as constituent elements, only the Li composition can be increased.

[0103] There is no particular limitation on the lithium nitride that can be used. Commercially available lithium nitride (such as Li3N, etc.) can be used. For example, lithium nitride obtained by the reaction of metallic lithium (such as Li foil) and nitrogen can be used. From the viewpoints of obtaining a high-purity solid electrolyte material and suppressing side reactions, lithium nitride with few impurities is preferably used.

[0104] Step (B1) of obtaining a glassy inorganic solid electrolyte material

[0105] Then, by mechanically treating the raw material composition of the inorganic solid electrolyte material, while causing the lithium sulfide, phosphorus sulfide, and, if necessary, lithium nitride as raw materials to undergo a chemical reaction, vitrification is carried out to obtain a glassy inorganic solid electrolyte material.

[0106] Mechanical treatment can cause a chemical reaction and vitrify by mechanically colliding two or more inorganic compounds. As the mechanical treatment, for example, mechanochemical treatment, etc. can be cited. Mechanochemical treatment is a method of vitrifying while applying mechanical energy such as shear force and collision force to the target composition.

[0107] In step (B1), from the viewpoint of easily achieving an environment where moisture and oxygen can be removed at a high level, the mechanochemical treatment is preferably a dry mechanochemical treatment.

[0108] By applying the mechanochemical treatment, it is possible to mix while pulverizing each raw material into fine particles. Therefore, the contact area of each raw material can be increased. Therefore, the reaction of each raw material can be promoted. Therefore, the inorganic solid electrolyte material of the present embodiment can be obtained more efficiently.

[0109] The mechanochemical treatment refers to a method of vitrification while applying mechanical energy such as shear force, collision force, or centrifugal force to the mixing object. As a device for vitrification by mechanochemical treatment (vitrification device), there can be mentioned grinding / dispersing machines such as ball mills, bead mills, vibration mills, turbo grinders, mechanical fusion machines, disk mills, and roller mills; rotary / striking crushing devices composed of a mechanism combining rotation (shearing stress) and striking (compressive stress) represented by rock drills, vibration drills, impact drivers, etc.; high-pressure type grinding rolls, etc. Among them, from the viewpoint of being able to efficiently generate very high impact energy, ball mills and bead mills are preferred, and ball mills are particularly preferred. In addition, from the viewpoint of excellent continuous productivity, roller mills are preferred; rotary / striking crushing devices composed of a mechanism combining rotation (shearing stress) and striking (compressive stress) represented by rock drills, vibration drills, impact drivers, etc.; high-pressure type grinding rolls; vertical mills such as roller vertical mills and ball vertical mills, etc.

[0110] It is preferred that step (B1) is carried out using a ball mill. When using a ball mill for step (B1), the balls used are preferably made of zirconia.

[0111] When using a ball mill for step (B1), from the viewpoints of the efficiency of the chemical reaction (mechanochemical reaction), particle size adjustment, etc., the diameter of the balls used is, for example, 10 to 50 mm, preferably 10 to 30 mm, and the material of the balls used is preferably zirconia.

[0112] When using a ball mill for step (B1), from the viewpoint of allowing the chemical reaction (mechanochemical reaction) to proceed sufficiently, the time is usually 10 hours or more, preferably 200 hours or more. In addition, from the viewpoints of efficiency / productivity, it is usually 1500 hours or less, preferably 800 hours or less.

[0113] Supplement the degree of vitrification. Generally, when performing X-ray diffraction analysis using CuKα rays as the radiation source, if the diffraction peaks from the raw materials disappear or decrease, it can be judged that the raw material inorganic composition has been vitrified, and the desired inorganic solid electrolyte material can be obtained.

[0114] In step (B1), it is preferable to perform vitrification until the lithium ion conductivity of the inorganic solid electrolyte material based on 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 is preferably 1.0×10 -4 S·cm -1 or more, more preferably 2.0×10 -4 S·cm -1 or more, and further preferably 3.0×10 - 4 S·cm -1 or more, particularly preferably 4.0×10 -4 S·cm -1 or more. Thus, an inorganic solid electrolyte material with further excellent lithium ion conductivity can be obtained.

[0115] Step (B2) of pulverizing and refining the obtained glassy inorganic solid electrolyte material

[0116] is preferably a step of appropriately pulverizing and refining the sufficiently vitrified inorganic solid electrolyte material in the above step (B1). Thus, it is easy to adjust D 10 to 0.54 to 0.80.

[0117] Step (B2) itself can be carried out using the same apparatus as in step (B1). It is preferable to use a ball mill for step (B2). By appropriately selecting conditions such as the material, diameter, and treatment time of the balls when treating with a ball mill, in particular, it is easy to adjust D 10 to 0.54 to 0.80. When using a ball mill for step (B2), it is preferable to use balls with a diameter sufficiently smaller than that of the balls used in step (B1) when using a ball mill. Specifically, at least a part of the balls used when using a ball mill for step (B2) is preferably 0.5 mm or more and 5 mm or less in diameter, more preferably 1 mm or more and 2 mm or less in diameter. In addition, when using a ball mill for step (B2), the balls used are preferably made of zirconia. It is speculated that by using balls of an appropriate size and material (hardness), the glassy inorganic solid electrolyte material is struck with "appropriate strength" and moderately refined, and in addition, particles with a moderate roundness with "corners removed" of the particles can be obtained.

[0118] Although it also depends on the treatment time of the ball mill, when using balls with too small a diameter (for example, balls with a diameter of 0.1 mm or less) for ball mill treatment, it is sometimes difficult to adjust D 10 to 0.54 to 0.80. The details are not yet clear. When using balls with too small a diameter, the particles are struck with a weak force and become too round, and it may be difficult to adjust D 10Adjust to 0.54 to 0.80.

[0119] There is no particular limitation on the time for the ball mill treatment in step (B2). The time is typically 0.1 to 500 hours. In addition, when the time for the ball mill treatment is too long, the particles are overly refined, and it is easy to form many deformed particles, and sometimes it is difficult to obtain D 10 Adjust to 0.54 to 0.80, so attention needs to be paid.

[0120] When performing the ball mill treatment in step (B2), the ball mill treatment using balls of different diameters can also be carried out in sequence. In this way, for example, particles with a smaller d50 can be obtained efficiently.

[0121] However, from the perspective of adjusting D 10 to 0.54 to 0.80, in the ball mill treatment, at least a part of the balls used is preferably 0.5 to 10 mm in diameter, more preferably 1 to 5 mm in diameter. In addition, the time for the ball mill treatment is preferably 1 to 100 hours, more preferably 10 to 70 hours. By ensuring that the diameter of the balls used for the ball mill treatment is not too small and / or the time for the ball mill treatment is not too long, it is easy to manufacture the inorganic solid electrolyte material of the present embodiment.

[0122] When performing the ball mill treatment, the ball mill treatment can also be temporarily interrupted, the powder adhering to the inner wall of the device and the balls can be scraped off, and the powder can be put into the balls again in the device to make the treatment more efficient.

[0123] There is no particular limitation on the amount of balls used in the ball mill treatment as long as sufficient treatment is carried out. Typically, 500 to 10,000 parts by mass of balls can be used relative to 100 parts by mass of the raw material composition.

[0124] In the present embodiment, it is preferable that step (B1) and step (B2) are carried out in an environment where the amounts and inflows of moisture and oxygen are suppressed at a higher level than in the past. Thereby, the contact between the raw material composition and moisture and oxygen can be suppressed at a higher level than in the past.

[0125] An environment where the amounts and inflows of moisture and oxygen are suppressed at a higher level than in the past can be formed, for example, by the following methods.

[0126] First, a mixing container and a sealed container for a vitrification device are arranged in a glove box. Then, the glove box is filled with and evacuated multiple times (preferably 3 times or more) with inert gases such as high-purity dry argon and dry nitrogen obtained through a gas purification device. Here, in the glove box after the above operations, high-purity dry argon, dry nitrogen and other inert gases are circulated through the gas purification device, and the oxygen concentration and moisture concentration are adjusted to preferably 1.0 ppm or less, more preferably 0.8 ppm or less, and further preferably 0.6 ppm or less.

[0127] Next, lithium sulfide and phosphorus sulfide are put into the mixing container in the glove box, and then a raw material composition is prepared by mixing (referring to step (A)). Here, lithium sulfide and phosphorus sulfide are put into the mixing container in the glove box according to the following steps. First, with the door inside the main body of the glove box closed, lithium sulfide and phosphorus sulfide are added to the side box of the glove box. Then, the side box is filled with and evacuated multiple times (preferably 3 times or more) with inert gases such as high-purity dry argon or dry nitrogen introduced from inside the glove box. Then, the door inside the main body of the glove box is opened, and lithium sulfide and phosphorus sulfide are placed into the mixing container inside the main body of the glove box, and the mixing container is sealed.

[0128] Next, after mixing lithium sulfide and phosphorus sulfide, the obtained raw material composition is taken out from the mixing container and transferred to a container for the vitrification device and sealed.

[0129] By performing such operations, the amount of moisture and oxygen present in the sealed container containing the raw material composition can be suppressed at a higher level than before. As a result, in steps (B1) and (B2), an environment can be formed in which the amount of moisture and oxygen present is suppressed at a higher level than before.

[0130] Then, the sealed container containing the raw material inorganic composition is taken out from the glove box. Next, the sealed container is placed in a vitrification device arranged in an environment filled with dry gases such as dry argon, dry nitrogen, and dry air (for example, in a box filled with dry argon, dry nitrogen, and dry air), and vitrification is performed. Here, it is preferable to continuously introduce a specified amount of dry gas into the environment filled with dry gas during vitrification. By making such improvements, in steps (B1) and (B2), an environment can be formed in which the inflow of moisture and oxygen is suppressed at a higher level than before.

[0131] From the perspective of highly suppressing the inflow of moisture and oxygen into the sealed container and from the perspective of achieving higher airtightness, it is preferable to use seals with excellent sealing performance such as O-rings and ferrule seals on the lid of the sealed container.

[0132] Classification treatment (screening) step (C)

[0133] Then, it is preferable to classify (screen) the obtained inorganic solid electrolyte material. By performing this treatment, it is easy to obtain particles with a d 50 of 10 μm or less and a D 10 of 0.54 to 0.80. The detailed situation is not yet clear. It is speculated that by performing the classification treatment (screening), not only some or all of the particles with larger particle sizes are removed, but also some or all of the particles with extremely small roundness are removed.

[0134] From the viewpoint of optimizing D 10 , d 50 , it is preferable to perform the classification treatment (screening) using a sieve with a mesh size of about 20 μm.

[0135] The inorganic solid electrolyte material can also be further pulverized to adjust the particle size, etc. As a specific method of the pulverization treatment, known pulverization methods such as jet milling, mortar, rotary mill, and coffee mill can be used.

[0136] From the viewpoint of being able to prevent contact with moisture in the air, it is preferable that step (C) is performed in an inert gas atmosphere or a vacuum atmosphere.

[0137] Step (D) of crystallizing at least a part of the inorganic solid electrolyte material

[0138] In the present embodiment, a step of crystallizing at least a part of the inorganic solid electrolyte material can also be performed. In step (D), by heating (annealing) the obtained glassy inorganic solid electrolyte material, at least a part of the inorganic solid electrolyte material is crystallized, thereby generating an inorganic solid electrolyte material in a glass-ceramic state (also referred to as crystallized glass). In this way, an inorganic solid electrolyte material with further excellent lithium ion conductivity can be obtained.

[0139] That is, from the viewpoint of excellent lithium ion conductivity, the inorganic solid electrolyte material of the present embodiment is preferably in a glass-ceramic state (crystallized glass state).

[0140] When heating (annealing) the glassy inorganic solid electrolyte material, the temperature 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.

[0141] The time for heating (annealing) the inorganic solid electrolyte material in a glass state is not particularly limited as long as it is a time sufficient to obtain the inorganic solid electrolyte material in a desired glass-ceramic state. For example, it is 0.5 hours or more and 24 hours or less, preferably 1 hour or more and 3 hours or less. The heating method is not particularly limited. For example, a method using a firing furnace can be cited. Conditions such as the heating temperature and time can be appropriately adjusted to optimize the properties of the inorganic solid electrolyte material.

[0142] Preferably, the heating (annealing) of the inorganic solid electrolyte material in a glass state is carried out in an inert gas atmosphere. Thereby, deterioration (e.g., oxidation) of the inorganic solid electrolyte material can be prevented. Examples of the inert gas include argon, helium, nitrogen, etc. For preventing impurities from mixing into the product, the higher the purity of these inert gases, the more preferable. In addition, for avoiding contact with moisture, the dew point is preferably -70°C or lower, particularly preferably -80°C or lower.

[0143] The method for introducing the inert gas is not particularly limited as long as it is a method for filling the system with an inert gas atmosphere. For example, a method of purging the inert gas, a method of continuously introducing a specified amount of the inert gas, etc. can be cited.

[0144] In order to obtain the inorganic solid electrolyte material of the present embodiment, it is preferable to appropriately adjust various conditions in the above-mentioned respective steps. However, the manufacturing method of the inorganic solid electrolyte material of the present embodiment is not limited to the above method, and the inorganic solid electrolyte material of the present embodiment can be obtained by appropriately adjusting various conditions.

[0145] <Solid Electrolyte>

[0146] The solid electrolyte of the present embodiment contains the above-mentioned inorganic solid electrolyte material of the present embodiment.

[0147] For the solid electrolyte of the present embodiment, as components other than the inorganic solid electrolyte material of the present embodiment, for example, within the scope not impairing the object of the present invention, it may contain a solid electrolyte material of a different type from the above-mentioned inorganic solid electrolyte material of the present embodiment, or may not contain it.

[0148] The solid electrolyte of this embodiment may or may not contain a solid electrolyte material different from the inorganic solid electrolyte material of this embodiment. As a solid electrolyte material different from the inorganic solid electrolyte material of this embodiment, as long as it has ion conductivity and insulation, there is no particular limitation, and a solid electrolyte material commonly used in lithium-ion batteries can be used. For example, inorganic solid electrolyte materials different from the inorganic solid electrolyte material of this embodiment, oxide-based inorganic solid electrolyte materials, other lithium-based inorganic solid electrolyte materials, etc. can be cited; organic solid electrolyte materials such as polymer electrolytes.

[0149] As an inorganic solid electrolyte material different from the aforementioned inorganic solid electrolyte material of this embodiment, for example, Li2S-P2S5 materials, Li2S-SiS2 materials, Li2S-GeS2 materials, Li2S-Al2S3 materials, Li2S-SiS2-Li3PO4 materials, Li2S-P2S5-GeS2 materials, Li2S-Li2O-P2S5-SiS2 materials, Li2S-GeS2-P2S5-SiS2 materials, Li2S-SnS2-P2S5-SiS2 materials, Li2S-P2S5-Li3N materials, Li2S 2+X -P4S3 materials, Li2S-P2S5-P4S3 materials, etc. These can be used alone or in combination of two or more.

[0150] Among them, from the viewpoint of excellent lithium ion conductivity and stability that does not cause decomposition in a wide voltage range, Li2S-P2S5 materials are preferred. Here, for example, the Li2S-P2S5 material refers to an inorganic material obtained by chemically reacting at least an inorganic composition containing Li2S (lithium sulfide) and P2S5 through mechanical treatment.

[0151] Here, in this embodiment, lithium sulfide also includes polysulfide.

[0152] As the above-mentioned oxide-based inorganic solid electrolyte materials, for example, NASICON types such as LiTi2(PO4)3, LiZr2(PO4)3, LiGe2(PO4)3, (La 0.5+x Li 0.5-3x )TiO3 and other perovskite types, Li2O-P2O5 materials, Li2O-P2O5-Li3N materials, etc. can be cited.

[0153] As other lithium-based inorganic solid electrolyte materials, for example, LiPON, LiNbO3, LiTaO3, Li3PO4, LiPO 4-x N x(where \(0 \lt x \leq 1\)), \(LiN\), \(LiI\), \(LISICON\), etc.

[0154] Furthermore, glass ceramics obtained by crystallizing and precipitating these inorganic solid electrolytes can also be used as inorganic solid electrolyte materials.

[0155] As the above-mentioned organic solid electrolyte materials, for example, dry polymer electrolytes, gel electrolytes and other polymer electrolytes can be used.

[0156] As the polymer electrolyte, the electrolyte commonly used in lithium-ion batteries can be used.

[0157] <Solid electrolyte membrane>

[0158] The solid electrolyte membrane of this embodiment contains a solid electrolyte as the main component, and the solid electrolyte contains the inorganic solid electrolyte material of the foregoing embodiment.

[0159] The solid electrolyte membrane of this embodiment is, for example, used to form the solid electrolyte layer of an all-solid-state lithium-ion battery.

[0160] As an example of an all-solid-state lithium-ion battery applying the solid electrolyte membrane of this embodiment, a battery in which a positive electrode, a solid electrolyte layer, and a negative electrode are laminated in this order can be cited. In this case, the solid electrolyte layer is composed of the solid electrolyte membrane.

[0161] The average thickness of the solid electrolyte membrane of this 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 above solid electrolyte membrane is above the above lower limit value, the loss of the solid electrolyte and the generation of cracks on the surface of the solid electrolyte membrane can be further suppressed. In addition, when the average thickness of the above solid electrolyte membrane is below the above upper limit value, the impedance of the solid electrolyte membrane can be further reduced. As a result, the battery characteristics of the obtained all-solid-state lithium-ion battery can be further improved.

[0162] The solid electrolyte membrane of this embodiment is preferably a compression molded body of particulate solid electrolyte containing the inorganic solid electrolyte material of the foregoing embodiment. That is, preferably, the particulate solid electrolyte is compressed to form a solid electrolyte membrane having a specified strength due to the anchoring effect between the solid electrolyte materials.

[0163] By forming a compression molded body, the solid electrolytes are bonded together, and the strength of the obtained solid electrolyte membrane is further improved. As a result, the loss of the solid electrolyte and the generation of cracks on the surface of the solid electrolyte membrane can be further suppressed.

[0164] When the total solid electrolyte membrane is 100% by mass, the content of the inorganic solid electrolyte material of the present embodiment in the solid electrolyte membrane of the present embodiment is preferably 50% by mass or more, more preferably 60% by mass or more, further preferably 70% by mass or more, still more preferably 80% by mass or more, and particularly preferably 90% by mass or more. Thereby, the contact between 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. Moreover, 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.

[0165] There is no particular limitation on the upper limit of the content of the inorganic solid electrolyte material of the present embodiment in the solid electrolyte membrane of the present embodiment, and it is, for example, 100% by mass or less.

[0166] There is no particular limitation on the planar shape of the solid electrolyte membrane, and it can be appropriately selected according to the shapes of the electrodes and current collectors. The planar shape can be, for example, rectangular.

[0167] A binder resin may be included in the solid electrolyte membrane of the present embodiment. When the binder resin is contained and the total solid electrolyte membrane is 100% by mass, its content is preferably less than 0.5% by mass, more preferably 0.1% by mass or less, further preferably 0.05% by mass or less, still more preferably 0.01% by mass or less. It is preferred that the solid electrolyte membrane of the present embodiment is substantially free of binder resin, and more preferably does not contain binder resin.

[0168] Thereby, the contact between 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. Moreover, 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.

[0169] For the sake of caution, "substantially free of binder resin" means that a binder resin may be contained to the extent that the effects of the present embodiment are not impaired. In addition, when an adhesive resin layer is provided between the solid electrolyte layer and the positive electrode or the negative electrode, the adhesive resin from the adhesive resin layer present near the interface between the solid electrolyte layer and the adhesive resin layer is excluded from the "binder resin in the solid electrolyte membrane".

[0170] The above-mentioned binder resin refers to a binder commonly used in lithium ion batteries for bonding inorganic solid electrolyte materials. For example, polyvinyl alcohol, poly(meth)acrylic acid, carboxymethyl cellulose, polytetrafluoroethylene, polyvinylidene fluoride, styrene-butadiene rubber, polyimide, etc. can be cited.

[0171] For example, (i) First, the particulate solid electrolyte is stacked in a film form on the surface of the cavity of the mold or on the surface of the substrate, and (ii) Next, the solid electrolyte stacked in a film form is pressurized, whereby the solid electrolyte film of the present embodiment can be obtained.

[0172] There is no particular limitation on the method of pressurizing the solid electrolyte in the above (ii). For example, when the particulate solid electrolyte is stacked on the surface of the cavity of the mold, pressurization based on the mold and the pressing die can be used; when the particulate solid electrolyte is stacked on the surface of the substrate, methods such as pressurization based on the mold and the pressing die, roll pressing, and flat pressing can be used. The pressure for pressurizing the solid electrolyte is, for example, 10 MPa or more and 500 MPa or less.

[0173] As needed, heating may also be performed simultaneously with the pressurization of the inorganic solid electrolyte stacked in a film form. As long as heat pressurization is performed, fusion and bonding between the solid electrolytes will occur, and the strength of the obtained solid electrolyte film will be further improved. As a result, the loss of the solid electrolyte and the generation of cracks on the surface of the solid electrolyte film can be further suppressed. The temperature for heating the solid electrolyte is, for example, 40 °C or more and 500 °C or less.

[0174] <Lithium-ion battery>

[0175] Figure 2 It is a cross-sectional view showing an example of the structure of the lithium-ion battery of the present embodiment (lithium-ion battery 10).

[0176] The lithium-ion battery 100 has, 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. Moreover, 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 inorganic solid electrolyte material of the present embodiment. Additionally, it is preferable that the positive electrode active material layer 101, the negative electrode active material layer 103, and the electrolyte layer 120 all contain the inorganic solid electrolyte material of the present embodiment.

[0177] In the present embodiment, unless otherwise specified, the layer containing the positive electrode active material is referred to as the positive electrode active material layer 101.

[0178] As needed, 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. Additionally, in the present embodiment, unless otherwise specified, the layer containing the negative electrode active material is referred to as the negative electrode active material layer 103. As needed, 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.

[0179] There is no particular limitation on the shape of the lithium-ion battery 100. Any other shapes such as cylindrical, coin-shaped, rectangular, film-shaped, etc. can be cited.

[0180] The lithium-ion battery 100 is manufactured by a generally well-known method. For example, the positive electrode 110, the electrolyte layer 120, and the negative electrode 130 are overlapped to form any other shapes such as cylindrical, coin-shaped, rectangular, film-shaped, etc., and if necessary, it is produced by enclosing a non-aqueous electrolyte.

[0181] (Positive electrode)

[0182] There is no particular limitation on the material constituting the positive electrode 110, and materials generally used for lithium-ion batteries can be used. There is no particular limitation on the manufacturing method of the positive electrode 110, and it can be manufactured by a generally well-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 aluminum foil.

[0183] Since the thickness and density of the positive electrode active material layer 101 are appropriately determined according to the use purpose of the battery, etc., there is no particular limitation, and it can be set according to generally well-known information.

[0184] The positive electrode active material layer 101 contains a positive electrode active material.

[0185] There is no particular limitation on the positive electrode active material, and generally well-known positive electrode active materials can be used. For example, lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMn2O4), solid solution oxide (Li2MnO3-LiMO2 (M = Co, Ni, etc.)), lithium-manganese-nickel oxide (LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O2), olivine-type lithium phosphorus oxide (LiFePO4) and other composite oxides; conductive polymers such as polyaniline and polypyrrole; sulfide-based positive electrode active materials such as Li2S, CuS, Li-Cu-S compounds, TiS2, FeS, MoS2, Li-Mo-S compounds, Li-Ti-S compounds, Li-V-S compounds, Li-Fe-S compounds; materials with sulfur as the active material such as sulfur-impregnated acetylene black, sulfur-impregnated porous carbon, and mixed powders of sulfur and carbon. These positive electrode active materials can be used alone or in combination of two or more.

[0186] Among them, from the viewpoint of having a higher discharge capacity density and more excellent cycle characteristics, sulfide-based positive electrode active materials are preferred, and one or more selected from Li-Mo-S compounds, Li-Ti-S compounds, and Li-V-S compounds are more preferred.

[0187] Here, the Li-Mo-S compound contains Li, Mo, and S as constituent elements, and can generally be obtained by mechanically treating inorganic compositions containing molybdenum sulfide and lithium sulfide as raw materials to cause a chemical reaction between them.

[0188] In addition, the Li-Ti-S compound contains Li, Ti, and S as constituent elements, and can generally be obtained by mechanically treating inorganic compositions containing titanium sulfide and lithium sulfide as raw materials to cause a chemical reaction between them.

[0189] The Li-V-S compound contains Li, V, and S as constituent elements, and can generally be obtained by mechanically treating inorganic compositions containing vanadium sulfide and lithium sulfide as raw materials to cause a chemical reaction between them.

[0190] For the positive electrode active material layer 101, as components other than the above positive electrode active material, for example, one or more materials selected from a binder resin, a thickener, a conductive aid, a solid electrolyte material, etc. may be included, or may not be included. Hereinafter, each material such as a binder resin, a thickener, a conductive aid, a solid electrolyte material, etc. will be described.

[0191] The positive electrode active material layer 101 may contain a binder resin having a function of bonding the positive electrode active materials to each other and bonding the positive electrode active materials to the current collector 105.

[0192] As long as the binder resin is a general binder resin that can be used in a lithium ion battery, there is no particular limitation. For example, polyvinyl alcohol, poly(meth)acrylic acid, carboxymethyl cellulose, polytetrafluoroethylene, polyvinylidene fluoride, styrene-butadiene rubber, polyimide, etc. can be cited. These binders can be used alone or in combination of two or more.

[0193] From the viewpoint of ensuring the fluidity of the slurry suitable for coating, the positive electrode active material layer 101 may also contain a thickener. As the thickener, as long as it is a general thickener that can be used in a lithium ion battery, there is no particular limitation. For example, cellulose-based polymers such as carboxymethyl cellulose, methyl cellulose, hydroxypropyl cellulose, and their ammonium salts and alkali metal salts, polycarboxylic acids, polyethylene oxide, polyvinylpyrrolidone, poly(meth)acrylate, polyvinyl alcohol, etc., which are water-soluble polymers, can be cited. The thickening agent can be used alone or in combination of two or more.

[0194] From the viewpoint of improving the conductivity of the positive electrode 110, the positive electrode active material layer 101 may contain a conductive additive. As the conductive additive, there is no particular limitation as long as it is a common conductive additive that can be used in a lithium-ion battery. For example, carbon blacks such as acetylene black and Ketjen black, and carbon materials such as vapor-grown carbon fibers can be cited. When using a conductive additive, one kind can be used alone, or two or more kinds can be used in combination.

[0195] The positive electrode 110 may contain a solid electrolyte containing the inorganic solid electrolyte material of the present embodiment described above, or may contain a solid electrolyte containing a solid electrolyte material different from the inorganic solid electrolyte material of the present embodiment. As the solid electrolyte material different from the inorganic solid electrolyte material of the present embodiment, there is no particular limitation as long as it has ion conductivity and insulation, and a solid electrolyte material commonly used in a lithium-ion battery can be used. For example, inorganic solid electrolyte materials such as inorganic solid electrolyte materials, oxide-based inorganic solid electrolyte materials, and other lithium-based inorganic solid electrolyte materials can be cited; organic solid electrolyte materials such as polymer electrolytes can be cited. More specifically, the inorganic solid electrolyte materials cited in the description of the solid electrolyte of the present embodiment can be used.

[0196] Since the mixing ratio of various materials in the positive electrode active material layer 101 is appropriately determined according to the use purpose of the battery, etc., there is no particular limitation, and it can be set according to generally known information.

[0197] (Negative electrode)

[0198] There is no particular limitation on the material constituting the negative electrode 130, and a material commonly used in a lithium-ion battery can be used. There is no particular limitation on the manufacturing method of the negative electrode 130, and 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.

[0199] Since the thickness and density of the negative electrode active material layer 103 are appropriately determined according to the use purpose of the battery, etc., there is no particular limitation, and it can be set according to generally known information.

[0200] The negative electrode active material layer 103 contains a negative electrode active material.

[0201] As the negative electrode active material, there is no particular limitation as long as it is a common negative electrode active material that can be used for the negative electrode of a lithium ion battery. For example, carbonaceous materials such as natural graphite, artificial graphite, resin carbon, carbon fiber, activated carbon, hard carbon, and soft carbon can be cited; metal-based materials mainly composed of lithium, lithium alloy, tin, tin alloy, silicon, silicon alloy, gallium, gallium alloy, indium, indium alloy, aluminum, aluminum alloy, etc.; conductive polymers such as polyacene, polyacetylene, and polypyrrole; lithium titanium composite oxide (for example, Li4Ti5O 12 ) and the like. These negative electrode active materials can be used alone or in combination of two or more.

[0202] There is no particular limitation on the negative electrode active material layer 103. As components other than the above negative electrode active material, for example, one or more materials selected from binder resins, thickeners, conductive aids, solid electrolyte materials, etc. can also be included. As these materials, there is no particular limitation, and for example, the same materials as those used in the above positive electrode 110 can be cited.

[0203] Since the mixing ratio of various materials in the negative electrode active material layer 103 is appropriately determined according to the use purpose of the battery, etc., there is no particular limitation and it can be set according to generally known information.

[0204] (Electrolyte layer)

[0205] The electrolyte layer 120 is a layer formed between the positive electrode active material layer 101 and the negative electrode active material layer 103.

[0206] As the electrolyte layer 120, a layer formed by impregnating a non-aqueous electrolyte into a separator or a solid electrolyte layer containing a solid electrolyte can be cited.

[0207] As the separator, there is no particular limitation as long as it electrically insulates the positive electrode 110 and the negative electrode 130 and has the function of allowing lithium ions to pass through. For example, a porous membrane can be used.

[0208] As the porous membrane, a microporous polymer membrane is preferably used. As the material, polyolefin, polyimide, polyvinylidene fluoride, polyester, etc. can be cited. In particular, a porous polyolefin membrane is preferably used. Specifically, a porous polyethylene membrane, a porous polypropylene membrane, etc. can be cited.

[0209] The non-aqueous electrolyte impregnated in the separator is an electrolytic solution formed by dissolving an electrolyte in a solvent. As the above electrolyte, any known lithium salt can be used as long as it is selected according to the type of active material. For example, LiClO4, LiBF6, LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiB 10 Cl10 , LiAlCl4, LiCl, LiBr, LiB(C2H5)4, CF3SO3Li, CH3SO3Li, LiCF3SO3, LiC4F9SO3, Li(CF3SO2)2N, lithium salts of lower fatty acids, etc.

[0210] There is no particular limitation as long as the solvent for dissolving the electrolyte is a solvent commonly used for dissolving electrolytes. For example, carbonate esters such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), vinylene carbonate (VC), etc.; lactones such as γ-butyrolactone, γ-valerolactone, etc.; ethers such as trimethoxymethane, 1,2-dimethoxyethane, diethyl ether, 2-ethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, etc.; sulfoxides such as dimethyl sulfoxide; oxolanes such as 1,3-dioxolane, 4-methyl-1,3-dioxolane; nitrogen-containing compounds such as acetonitrile, nitromethane, formamide, dimethylformamide; organic acid esters such as methyl formate, methyl acetate, ethyl acetate, butyl acetate, methyl propionate, ethyl propionate; phosphate triesters, diglyme; triglyme; sulfolanes such as sulfolane, methylsulfolane; oxazolidinones such as 3-methyl-2-oxazolidinone; sultones such as 1,3-propane sultone, 1,4-butane sultone, naphthalene sulfonic acid lactone, etc. These materials can be used alone or in combination of two or more.

[0211] The solid electrolyte layer 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. There is no particular limitation as long as the solid electrolyte contained in the solid electrolyte layer has lithium ion conductivity. However, in the present embodiment, it is preferably a solid electrolyte containing the inorganic solid electrolyte material of the present embodiment.

[0212] There is no particular limitation as long as the content of the solid electrolyte in the solid electrolyte layer of the present embodiment is in a proportion that can obtain the desired performance, for example, 10% by volume or more and 100% by volume or less, preferably 50% by volume or more and 100% by volume or less. In particular, in the present embodiment, it is preferred that the solid electrolyte layer is composed only of a solid electrolyte containing the inorganic solid electrolyte material of the present embodiment.

[0213] The solid electrolyte layer of this embodiment may also contain an adhesive resin. By containing the adhesive resin, a flexible solid electrolyte layer can be obtained. Examples of the adhesive resin include fluorine-containing binder materials such as polytetrafluoroethylene and polyvinylidene fluoride. The thickness of the solid electrolyte layer is, for example, 0.1 μm or more and 1000 μm or less, preferably 0.1 μm or more and 300 μm or less.

[0214] The embodiments of the present invention have been described above, but these are examples of the present invention, and various configurations other than the above can also be adopted. In addition, the present invention is not limited to the foregoing embodiments, and modifications, improvements, etc. within the scope that can achieve the object of the present invention are also included in the present invention.

[0215] Examples

[0216] The embodiments of the present invention will be described in detail based on examples and comparative examples. For the sake of caution, the present invention is not limited only to the examples.

[0217] <Example 1>

[0218] An inorganic solid electrolyte material was manufactured through the following steps.

[0219] (1) Preparation of raw materials

[0220] Li2S (manufactured by Furukawa Machinery Metal Co., Ltd., purity 99.9%), P2S5 (manufactured by Kanto Chemical Co., Inc.), and Li3N (manufactured by Furukawa Machinery Metal Co., Ltd.) were prepared respectively.

[0221] (2) Weighing and mixing with a mortar

[0222] Next, in an argon glove box, Li2S powder, P2S5 powder, and Li3N powder (Li2S:P2S5:Li3N = 27:9:2 (molar ratio)) were precisely weighed, and these powders were mixed with an agate mortar for 10 minutes. Thus, a mixed powder was obtained.

[0223] (3) Vitrification: Mechanochemical treatment (grinding and mixing) using a ball mill

[0224] Next, 500 g of the mixed powder obtained in the above (2) was weighed and placed in an alumina container (inner volume 5.0 L) together with 7500 g of zirconia balls with a diameter of φ25 mm and 700 g of zirconia balls with a diameter of φ10 mm. Then, mechanochemical treatment (grinding and mixing) was performed with a ball mill (rotation speed 100 rpm) for 48 hours.

[0225] Next, scrape the pulverized and mixed powder adhering to the inner wall of the container and the balls. Then, put the powder and the balls into the same container again, and perform mechanochemical treatment (pulverization and mixing) with a ball mill (rotation speed 100 rpm) for the same time as before. Repeat the operation from scraping to mechanochemical treatment (pulverization and mixing) until the cumulative time reaches 700 hours. In the above-described manner, an inorganic solid electrolyte material in a glass state (Li 10 P3S 12 ) is obtained.

[0226] The mechanochemical treatment (pulverization and mixing) is carried out in an environment where the amounts and inflows of moisture and oxygen are highly suppressed.

[0227] (4) Annealing treatment

[0228] Anneal 300 g of the obtained inorganic solid electrolyte material in a glass state at 300 °C for 7 hours in argon. Thus, an inorganic solid electrolyte material in a glass-ceramic state (Li 10 P3S 12 ) is obtained.

[0229] (5) Sieving

[0230] Next, in argon, classify the obtained inorganic solid electrolyte material in a glass-ceramic state through a sieve with a mesh size of 20 μm (remove the components that cannot pass through the sieve).

[0231] In summary, an inorganic solid electrolyte material is obtained.

[0232] <Example 2>

[0233] Except that the inorganic solid electrolyte material in a glass state obtained in the above (3) is also classified through a sieve with a mesh size of 20 μm before the annealing treatment, the same procedure as in Example 1 is carried out to obtain an inorganic solid electrolyte material in a glass-ceramic state.

[0234] (That is, in Example 2, sieving is carried out a total of 2 times before and after the annealing treatment.)

[0235] <Example 3>

[0236] In Example 3, the foregoing process (B2) is carried out. That is, the inorganic solid electrolyte material in a glass state obtained in (3) of Example 1 is further pulverized and refined under appropriate conditions. The specific situation is as follows.

[0237] Weigh 300 g of the glassy inorganic solid electrolyte material obtained by pulverization and mixing in Example 1(3) using a ball mill, and put it together with 1200 g of zirconia balls with a diameter of φ5 mm, 6200 g of zirconia balls with a diameter of φ2 mm, and 1200 g of zirconia balls with a diameter of φ1 mm into an alumina container (internal volume 5 L). While shaking with a ball mill (rotation speed 100 rpm), pulverize for 50 hours to obtain a glassy inorganic solid electrolyte material. By annealing this glassy inorganic solid electrolyte material in argon at 300 °C for 7 hours, a glass-ceramic inorganic solid electrolyte material (Li 10 P3S 12 ) is obtained.

[0238] Next, classify the obtained glass-ceramic inorganic solid electrolyte material through a sieve with a mesh size of 20 μm.

[0239] As described above, a glass-ceramic inorganic solid electrolyte material is obtained.

[0240] <Comparative Example 1>

[0241] Although the foregoing step (B2) was carried out in Comparative Example 1, since the conditions were inappropriate, it was an example in which particles with D 10 ranging from 0.54 to 0.80 could not be obtained. The specific situation is as follows.

[0242] Weigh 400 g of the glassy inorganic solid electrolyte material obtained by pulverization and mixing in Example 1(3) using a ball mill, and put it together with 6200 g of zirconia balls with a diameter of φ2 mm into an alumina container (internal volume 5 L). While shaking with a ball mill (rotation speed 100 rpm), pulverize for 120 hours to obtain a glassy inorganic solid electrolyte material. By annealing this glassy inorganic solid electrolyte material in argon at 300 °C for 7 hours, a glass-ceramic inorganic solid electrolyte material (Li 10 P3S 12 ) is obtained.

[0243] Next, classify the obtained glass-ceramic inorganic solid electrolyte material through a sieve with a mesh size of 20 μm.

[0244] As described above, a glass-ceramic inorganic solid electrolyte material is obtained.

[0245] <Comparative Example 2>

[0246] Weigh 400 g of the glassy inorganic solid electrolyte material obtained by pulverization and mixing in Example 1 (3) using a ball mill, and put it together with 6200 g of zirconia balls with a diameter of φ2 mm into an alumina container (internal volume: 5 L). While shaking with a ball mill (rotation speed: 100 rpm), pulverize for 120 hours to obtain a glassy inorganic solid electrolyte material. By annealing this glassy inorganic solid electrolyte material in argon at 300 °C for 7 hours, a glass-ceramic inorganic solid electrolyte material (Li 10 P3S 12 ) is obtained.

[0247] Next, the obtained glass-ceramic inorganic solid electrolyte material is classified through a sieve with a mesh size of 20 μm. Then, the material remaining on this "oversize" is used as the final inorganic solid electrolyte material.

[0248] <Comparative Example 3>

[0249] The inorganic solid electrolyte material of Comparative Example 3 is manufactured through the following steps. Comparative Example 3 is an example of manufacturing an inorganic solid electrolyte material according to Paragraph 0126 of the aforementioned Patent Document 1 and Example 106 in Table 1.

[0250] As raw materials, Li2S (manufactured by Furukawa Machinery Metal Co., Ltd., purity: 99.9%) and P2S5 (manufactured by Kanto Chemical Co., Inc.) are used respectively.

[0251] First, inside an argon glove box, precisely weigh Li2S powder and P2S5 powder (Li2S:P2S5 = 75:25 (molar ratio)), and mix these powders with an agate mortar for 10 minutes.

[0252] Next, weigh 2 g of the mixed powder, put it together with 18 zirconia balls with a diameter of φ10 mm into a zirconia container (internal volume: 45 mL), and pulverize and mix (mechanochemical treatment) for 30 hours using a planetary ball mill (rotation speed of the main shaft: 800 rpm, rotation speed of the planetary motion: 400 rpm).

[0253] In summary, a glassy inorganic solid electrolyte material (Li9P3S 12 ) is obtained.

[0254] <Measurement of the circularity of particles / calculation of the frequency distribution of circularity, measurement of the particle size of particles / calculation of the particle size distribution>

[0255] Use the image processing software publicly available from the National Institutes of Health (open source software, ImageJ, v1.52a) to analyze the SEM images of the obtained inorganic solid electrolyte material. Then, based on this analysis, calculate the frequency distribution of the circularity of particles and the particle size distribution.

[0256] Based on the obtained frequency distribution, calculate D 10 , D 50 , D 90 , and (D 90 - D 10 ) / D 50 . Additionally, based on the obtained particle size distribution, calculate d 10 , d 50 , and d 90 .

[0257] As a step, first, attach a carbon tape to the specimen stage of the SEM, and make the particles of the trace inorganic solid electrolyte material adhere to the carbon tape in a thin and widely dispersed state.

[0258] Then, take a photograph of the SEM image of the inorganic solid electrolyte material (resolution: 1280 × 960 pixels horizontally, magnification appropriately adjusted from 250 to 1000 times). Read the obtained SEM image into ImageJ. Perform calibration according to the scale shown in the SEM image. Then, convert the image into a black-and-white binary image. At this time, set the threshold value to make the contour of the particles clear. When there are overlapping particles in the obtained black-and-white image, as image processing based on ImageJ, separate the overlapping particles between the particles by the watershed method. Moreover, as image analysis based on ImageJ, perform particle analysis to obtain the measurement results based on the circularity "Circ." and the measurement results of the particle size of the Feret diameter.

[0259] Read the obtained measurement results of circularity into the spreadsheet software EXCEL (registered trademark) of Microsoft Corporation, arrange the circularity in ascending order, and obtain the frequency distribution by calculating its number. Similarly, based on the obtained measurement results of the particle size, obtain the particle size distribution.

[0260] In each example and comparative example, take multiple SEM images, and measure the circularity and particle size of a total of more than 3000 particles respectively, so as to obtain the frequency distribution of circularity and the particle size distribution.

[0261] <Evaluation: Measurement of Lithium Ion Conductivity>

[0262] For the inorganic solid electrolyte materials obtained in each example and comparative example, measure the lithium ion conductivity by the alternating current impedance method.

[0263] The measurement of lithium ion conductivity uses a potentiostat / galvanostat SP-300 manufactured by Bio-Logic. The size of the specimen is 9.5 mm in diameter and 1.2 - 2.0 mm in thickness. The measurement conditions are an applied voltage of 10 mV, a measurement temperature of 27.0 °C, a measurement frequency range of 0.1 Hz - 7 MHz, and the electrode is a Li foil.

[0264] As a sample for measuring lithium ion conductivity, a plate-shaped inorganic solid electrolyte material with a diameter of 9.5 mm and a thickness of 1.2 to 2.0 mm is used. This plate-shaped inorganic solid electrolyte material is obtained by pressing 150 mg of the powdery inorganic solid electrolyte material obtained in each example and comparative example under the conditions of 270 MPa and 10 minutes using a pressing device.

[0265] Various information is summarized in Table 1.

[0266] Table 1

[0267]

[0268] As shown in Table 1, the inorganic solid electrolyte materials (Examples 1 to 3) containing sulfide-based inorganic solid electrolyte particles with D 10 ranging from 0.54 to 0.80 and d 50 ranging from 0.1 to 10 μm have a relatively large lithium ion conductivity.

[0269] On the other hand, compared with Examples 1 to 3, the inorganic solid electrolyte materials (Comparative Examples 1 to 3) containing sulfide-based inorganic solid electrolyte particles with D 10 less than 0.54 and / or d 50 greater than 10 μm have a poorer lithium ion conductivity.

[0270] The examples and comparative examples are examined.

[0271] It is also considered that in Examples 1 to 3, the d 50 of Example 3 is the smallest, with many particle interfaces, so the lithium ion conductivity is relatively small. However, the largest lithium ion conductivity is shown in Examples 1 to 3. It is considered that this is because the D 10 of Example 3 is larger than that of Examples 1 and 2. That is, it is considered that based on the comparison between Example 3 and Examples 1 and 2, the index of D 10 is closely related to the lithium ion conductivity.

[0272] For Comparative Examples 1 to 3, it is considered that due to inappropriate conditions of the ball mill treatment in the pulverization process or lack of proper screening operation, sulfide-based inorganic solid electrolyte particles with D 10 ranging from 0.54 to 0.80 and d 50 ranging from 0.1 to 10 μm cannot be manufactured. Moreover, as a result, it is considered that the lithium ion conductivity is poorer compared with Examples 1 to 3.

[0273] In particular, based on the comparison between Example 1 and Comparative Example 1, when the inorganic solid electrolyte material in a glass state is "simply crushed finer", the particle size becomes smaller, but the ionic conductivity deteriorates. On the other hand, in Example 3, a crushing treatment was also added to Example 1, and compared with Comparative Example 1, d 50 is smaller, and the ionic conductivity is improved. From these situations, it can also be understood that the index of "the 10% cumulative value D 10 in the frequency distribution of circularity" is closely related to the improvement of ionic conductivity.

[0274] This application claims the priority based on Japanese Patent Application No. 2020-197942 filed on November 30, 2020, and the entire content of this Japanese patent application is incorporated herein by reference.

[0275] Description of Reference Numerals

[0276] 100: Lithium ion battery.

[0277] 101: Positive electrode active material layer.

[0278] 103: Negative electrode active material layer.

[0279] 105: Current collector.

[0280] 110: Positive electrode.

[0281] 120: Electrolyte layer.

[0282] 130: Negative electrode.

Claims

1. An inorganic solid electrolyte material, which is an inorganic solid electrolyte material containing sulfide-based inorganic solid electrolyte particles, wherein, In the frequency distribution of the circularity of the particles where the circularity of the particles in the material is plotted on the horizontal axis and the frequency on a number basis is plotted on the vertical axis, the 10% cumulative value D 10 is 0.54 to 0.80, and the 90% cumulative value D 90 is 0.85 to 0.

95. The median particle size d based on the number of particles in the material 50 is 0.1 to 6.0 μm.

2. The inorganic solid electrolyte material according to claim 1, wherein, The 50% cumulative value D in the frequency distribution 50 is less than 0.

85.

3. The inorganic solid electrolyte material according to claim 1 or 2, wherein, Set the 50% cumulative value in the frequency distribution as D 50 and set the 90% cumulative value in the frequency distribution as D 90 When, (D 90 - D 10 ) / D 50 The value of is 0.10 to 0.

45.

4. The inorganic solid electrolyte material according to any one of claims 1 to 3, wherein, the inorganic solid electrolyte material contains Li, P, and S as constituent elements.

5. The inorganic solid electrolyte material according to claim 4, wherein, in the inorganic solid electrolyte material, the molar ratio of Li to P, Li / P, is 1.0 or more and 5.0 or less, and the molar ratio of S to P, S / P, is 2.0 or more and 6.0 or less.

6. The inorganic solid electrolyte material according to any one of claims 1 to 5, wherein, the inorganic solid electrolyte material is used in a lithium-ion battery.

7. A solid electrolyte, wherein, the solid electrolyte contains the inorganic solid electrolyte material according to any one of claims 1 to 6.

8. A solid electrolyte membrane, wherein, the solid electrolyte membrane contains the solid electrolyte according to claim 7 as a main component.

9. The solid electrolyte membrane according to claim 8, wherein, the solid electrolyte membrane is a compression molded body of particulate solid electrolyte.

10. The solid electrolyte membrane according to claim 8 or 9, wherein, when the entire solid electrolyte membrane is set to 100% by mass, the content of the binder resin in the solid electrolyte membrane is less than 0.5% by mass.

11. The solid electrolyte membrane according to any one of claims 8 to 10, wherein, when the entire solid electrolyte membrane is set to 100% by mass, the content of the inorganic solid electrolyte material in the solid electrolyte membrane is 50% by mass or more.

12. A lithium-ion battery, which is a lithium-ion battery having a positive electrode including a positive electrode active material layer, an electrolyte layer, and a negative electrode including a negative electrode active material layer, wherein, at least one of the positive electrode active material layer, the electrolyte layer, and the negative electrode active material layer contains the inorganic solid electrolyte material according to any one of claims 1 to 6.

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