Sulfide solid electrolyte particles and all-solid-state battery

Abstract

The invention relates to sulfide solid electrolyte particles and an all-solid-state battery. Provided are: sulfide solid electrolyte particles which have sufficient ion conductivity and are capable of suppressing the rate of resistance increase after a charge / discharge cycle when used in an all-solid-state battery; and an all-solid-state battery which is provided with the sulfide solid electrolyte particles. Sulfide solid electrolyte particles which contain a sulfide solid electrolyte containing Li, P, S and a halogen as constituent elements, and which have an oxygen / sulfur element ratio of 0.79-1.25 (inclusive) on the surface as measured by XPS, and an oxygen / sulfur element ratio of 0.58 or less at a position 30 nm from the surface (in terms of SiO2 sputtering rate).

Description

[0001] This application is a divisional application of a Chinese patent application with an application date of January 14, 2020, an application number of 202010035817.8, and an invention title of "Sulfide Solid Electrolyte Particles and All-Solid-State Batteries". Technical Field

[0002] This disclosure relates to sulfide solid electrolyte particles and all-solid-state batteries. Background Art

[0003] It is considered that all-solid-state batteries such as all-solid-state lithium secondary batteries obtained by replacing liquid electrolytes with solid electrolytes simplify safety devices because they do not use flammable organic solvents in the battery, and are excellent in manufacturing cost and productivity.

[0004] In the battery constituent group of such all-solid-state batteries, since the positive electrode, negative electrode, and electrolyte are all solid, compared with, for example, a lithium secondary battery using an organic electrolyte solution, there is a tendency for the resistance to increase and the output current to decrease.

[0005] Therefore, in order to increase the output current of an all-solid-state lithium secondary battery, an electrolyte with high ionic conductivity is preferably used as the electrolyte. It is considered that in sulfide solid electrolytes, since sulfide ions are ions with a larger polarizability than oxide ions and have a smaller electrostatic attraction to lithium ions, they exhibit higher ionic conductivity than oxide solid electrolytes.

[0006] However, in a battery using the above-mentioned sulfide solid electrolyte material, there are the following problems: when in contact with an oxide active material, a high-resistance portion is generated at the interface between the sulfide solid electrolyte material and the oxide active material, and the sulfide solid electrolyte material is prone to deterioration.

[0007] A sulfide solid electrolyte material is disclosed in Patent Document 1, which includes: a sulfide layer containing a sulfide material, and an oxide layer containing an oxide formed by oxidizing the sulfide material. The oxide layer is located on the surface of the sulfide layer. When the oxygen / sulfur element ratio of the outermost surface of the oxide layer measured by XPS depth profile analysis is set as x, and the oxygen / sulfur element ratio of the position 32 nm from the outermost surface of the oxide layer measured by the XPS depth profile analysis and converted by the SiO2 sputtering rate is set as y, 1.28 ≤ x ≤ 4.06 and x / y ≥ 2.60 are satisfied. Patent Document 1 describes that by sufficiently increasing the proportion of oxygen bonds at the outermost surface of the sulfide solid electrolyte material within the specific range, the electrolysis of the sulfide solid electrolyte material at the outermost surface of the sulfide solid electrolyte material that may be exposed to a high potential due to contact with an active material or the like can be sufficiently suppressed; in the oxide layer near the interface where the oxide layer and the sulfide layer are in contact, by reducing oxygen bonds within the specific range, high ionic conductivity can be maintained, and as a result, the charge-discharge characteristics of the battery can be further improved.

[0008] In addition, a sulfide solid electrolyte particle is disclosed in Patent Document 2, which is characterized in that an oxide layer formed by oxidizing itself is provided on the surface and contains a sulfide solid electrolyte material. Patent Document 2 describes that the oxygen / sulfur element ratio on the surface of the sulfide solid electrolyte particle is preferably 2 times or more than the oxygen / sulfur element ratio at a position 30 nm from the surface; since the generation of a high-resistance portion at the interface between the sulfide solid electrolyte particle and the oxide active material can be suppressed and the deterioration of the sulfide solid electrolyte particle can be suppressed, the durability of the all-solid-state battery can be improved.

[0009] Prior Art Documents

[0010] Patent Documents

[0011] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2018-26321

[0012] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2012-94445 Summary of the Invention

[0013] Problems to be Solved by the Invention

[0014] However, in reality, in the sulfide solid electrolyte material with a high surface oxygen ratio as disclosed in Patent Document 1, the ionic conductivity of the solid electrolyte decreases sharply. In a all-solid-state battery using such a sulfide solid electrolyte material with low ionic conductivity, instead, the interfacial resistance between the sulfide solid electrolyte material and the oxide active material increases significantly, and the initial resistance becomes extremely high. Therefore, it can only operate at an extremely low charge-discharge rate as described in Patent Document 1, which poses a problem in practical use.

[0015] Even the sulfide solid electrolyte particles disclosed in Patent Document 2 are not sufficient in terms of having sufficient ionic conductivity and suppressing the rate of increase in resistance after charge-discharge cycles, and improvement is desired.

[0016] In view of the above actual situation, the present disclosure provides sulfide solid electrolyte particles having sufficient ionic conductivity and capable of suppressing the rate of increase in resistance after charge-discharge cycles when used in an all-solid-state battery, and an all-solid-state battery including an electrode or a solid electrolyte layer containing such sulfide solid electrolyte particles.

[0017] Means for Solving the Problem

[0018] The sulfide solid electrolyte particles of the present disclosure are characterized in that they contain a sulfide solid electrolyte containing Li, P, S, and a halogen as constituent elements, and the oxygen / sulfur element ratio on the surface of the sulfide solid electrolyte particles measured by XPS is 0.79 or more and 1.25 or less, and the oxygen / sulfur element ratio at a position 30 nm (converted at the SiO2 sputtering rate) from the surface is 0.58 or less.

[0019] In the sulfide solid electrolyte particles of the present disclosure, the sulfide solid electrolyte particles may contain a sulfide solid electrolyte containing Li, P, S, I, and Br as constituent elements.

[0020] The all-solid-state battery of the present disclosure includes a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, and is characterized in that

[0021] at least one of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer contains the sulfide solid electrolyte particles.

[0022] Advantageous Effects of the Invention

[0023] According to the present disclosure, it is possible to provide sulfide solid electrolyte particles having sufficient ionic conductivity and capable of suppressing the rate of increase in resistance after charge-discharge cycles when used in an all-solid-state battery, and an all-solid-state battery including an electrode or a solid electrolyte layer containing such sulfide solid electrolyte particles. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic cross-sectional view showing an example of the structure of the sulfide solid electrolyte particles of the present disclosure.

[0025] Figure 2 Schematic cross-sectional view showing an example of the power generation element of the all-solid-state battery of the present disclosure.

[0026] Symbol Explanation

[0027] 1 Sulfide solid electrolyte particles

[0028] 2 Oxide layer

[0029] 3 Sulfide solid electrolyte material

[0030] 11 Positive electrode layer

[0031] 12 Negative electrode layer

[0032] 13 Solid electrolyte layer

[0033] 20 Positive electrode active material

[0034] 100 Power generation element Detailed Description of the Invention

[0035] 1. Sulfide solid electrolyte particles

[0036] The sulfide solid electrolyte particles of the present disclosure are characterized in that they contain a sulfide solid electrolyte containing Li, P, S, and a halogen as constituent elements, and the oxygen / sulfur element ratio on the surface of the sulfide solid electrolyte particles measured by XPS is 0.79 or more and 1.25 or less, and the oxygen / sulfur element ratio at a position 30 nm (converted at the SiO2 sputtering rate) from the surface is 0.58 or less.

[0037] Since the oxygen / sulfur element ratio on the surface of the sulfide solid electrolyte particles of the present disclosure measured by XPS is 0.79 or more and 1.25 or less, and the oxygen / sulfur element ratio at a position 30 nm (converted at the SiO2 sputtering rate) from the surface is 0.58 or less, the oxygen / sulfur element ratio on the particle surface is higher than that inside the particle, and the surface is oxidized. Regarding the sulfide solid electrolyte particles of the present disclosure, a form in which an oxide layer formed by self-oxidation is present on the surface of the sulfide solid electrolyte can be cited.

[0038] An example of the sulfide solid electrolyte particles of the present disclosure will be described with reference to the accompanying drawings. It should be noted that in the drawings attached to this specification, for the convenience of illustration and easy understanding, the scale, the aspect ratio, etc. are appropriately changed and enlarged from the actual object.

[0039] As Figure 1As shown, the sulfide solid electrolyte particles 1 of the present disclosure may include sulfide solid electrolyte particles in which an oxide layer 2 obtained by oxidation covers the surface of particles (sulfide solid electrolyte material) 3 composed of a sulfide solid electrolyte containing Li, P, S, and a halogen as constituent elements.

[0040] In the sulfide solid electrolyte particles of the present disclosure, by oxidizing the surface, the oxygen / sulfur element ratio at the surface of the sulfide solid electrolyte containing Li, P, S, and a halogen as constituent elements and at a position 30 nm away from the surface satisfies the specific value, thereby having sufficient ionic conductivity and being able to suppress the increase rate of resistance after charge-discharge cycles when used in all-solid-state batteries.

[0041] The sulfide solid electrolyte containing Li, P, S, and a halogen as constituent elements used in the sulfide solid electrolyte particles of the present disclosure can achieve high ionic conductivity by containing a halogen, compared with a sulfide solid electrolyte containing Li, P, and S and not containing a halogen. When the surface of the sulfide solid electrolyte is oxidized, the ionic conductivity decreases. However, in the present disclosure, it is considered that by appropriately oxidizing the surface of the sulfide solid electrolyte containing Li, P, S, and a halogen with high ionic conductivity less than before, the decrease in ionic conductivity can be suppressed, and thus sufficient ionic conductivity can be obtained. In addition, by appropriately oxidizing the surface of the sulfide solid electrolyte containing Li, P, S, and a halogen with high ionic conductivity less than before, during charge-discharge of all-solid-state batteries, the reaction at the interface between the sulfide solid electrolyte particles and the oxide active material is suppressed, and their respective chemical deterioration is suppressed, so that the increase rate of resistance after charge-discharge cycles can be suppressed.

[0042] [Oxygen / sulfur element ratio]

[0043] The oxygen / sulfur element ratio of the surface of the sulfide solid electrolyte particles of the present disclosure measured by XPS is 0.79 or more and 1.25 or less.

[0044] When the oxygen / sulfur element ratio of the surface measured by XPS in the sulfide solid electrolyte containing the specific one is less than 0.79, it is difficult to obtain the effect of suppressing the reaction at the interface between the sulfide solid electrolyte particles and the oxide active material, so there is a possibility that the increase rate of resistance after charge-discharge cycles cannot be sufficiently suppressed.

[0045] On the other hand, when the oxygen / sulfur element ratio of the surface measured by XPS in the sulfide solid electrolyte containing the specific one is greater than 1.25, there is a possibility that the ionic conductivity of the sulfide solid electrolyte particles decreases sharply. From the aspect of obtaining excellent ionic conductivity, for the sulfide solid electrolyte particles of the present disclosure, it is preferable that the oxygen / sulfur element ratio of the surface measured by XPS is 1.00 or less.

[0046] In addition, for the sulfide solid electrolyte particles of the present disclosure, the oxygen / sulfur element ratio at a position 30 nm from the surface (converted at the SiO2 sputtering rate) measured by XPS is 0.58 or less. Since the oxygen / sulfur element ratio at a position 30 nm from the surface (converted at the SiO2 sputtering rate) is 0.58 or less, a decrease in the ionic conductivity of the sulfide solid electrolyte particles can be suppressed, and good ionic conductivity can be maintained. As long as the oxygen / sulfur element ratio on the surface is within the specific range, the lower limit of the oxygen / sulfur element ratio at a position 30 nm from the surface (converted at the SiO2 sputtering rate) is not particularly limited. The oxygen / sulfur element ratio at a position 30 nm from the surface (converted at the SiO2 sputtering rate) can be 0.00, and the lower limit can be about 0.20.

[0047] In the present disclosure, the oxygen / sulfur element ratio is a value measured based on XPS (X-ray photoelectron spectroscopy). XPS can be measured using, for example, an XPS apparatus (manufactured by ULVAC, Inc., ULVAC-PHI).

[0048] In the XPS apparatus, depth-direction analysis can also be performed using a combination of XPS and sputtering. Specifically, while sputtering at a constant sputtering rate, XPS measurement is performed, a depth profile obtained by graphing the relationship between the sputtering time and the XPS intensity is prepared in advance, and the thickness from the surface is calculated from the value of the sputtering rate obtained by the measurement, and the oxygen / sulfur element ratio at this position can be measured.

[0049] In the case where the sulfide solid electrolyte particles of the present disclosure have an oxide layer formed by self-oxidation on the surface of the sulfide solid electrolyte, generally, the oxygen / sulfur element ratio continuously decreases as the depth from the surface progresses and gradually converges to the oxygen / sulfur element ratio of the sulfide solid electrolyte itself. Such a case where the surface of the sulfide solid electrolyte has an oxide layer formed by self-oxidation is preferable in terms of preventing adverse conditions such as peeling of the oxide layer.

[0050] [Sulfide solid electrolyte]

[0051] In the sulfide solid electrolyte particles of the present disclosure, a sulfide solid electrolyte containing Li (lithium), P (phosphorus), S (sulfur), and a halogen as constituent elements is used. For the sulfide solid electrolyte particles of the present disclosure, examples of the sulfide solid electrolyte used include Li2S-P2S5-LiX type sulfide solid electrolytes obtained from Li2S, P2S5, and LiX (where X is one or more atoms selected from the group consisting of halogens).

[0052] The halogen may be one or more atoms selected from the group consisting of F (fluorine), Cl (chlorine), Br (bromine), and I (iodine). As the halogen, from the aspect of ionic conductivity, one or more selected from the group consisting of I, Br, and Cl are preferred.

[0053] As the sulfide solid electrolyte containing Li, P, S, and a halogen as constituent elements, a sulfide solid electrolyte having a composition represented by, for example, the general formula a(LiX)･(1-a)(bLi2S･(1-b)P2S5) obtained by converting the Li, P, S, and halogen (X) with Li2S, P2S5, and LiX can be cited. It should be noted that a corresponds to the total molar ratio of LiX with respect to the total moles of LiX, Li2S, and P2S5, and b corresponds to the molar ratio of Li2S with respect to the total moles of Li2S and P2S5.

[0054] As a, from the aspect of the composition range capable of obtaining high ionic conductivity, it can be cited as 0.1 or more and 0.3 or less, and further can be cited as 0.15 or more and 0.25 or less.

[0055] In addition, as b, from the aspect of the composition range for precipitating high ionic conductivity crystals, it can be cited as 0.72 or more and 0.78 or less, and further can be cited as 0.74 or more and 0.76 or less.

[0056] In the sulfide solid electrolyte containing Li, P, S, and a halogen as constituent elements, two or more halogens may be contained.

[0057] Among them, from the aspect of ionic conductivity, a sulfide solid electrolyte containing Li, P, S, I, and Br as constituent elements is preferred, and a Li2S-P2S5-LiI-LiBr type sulfide solid electrolyte obtained from Li2S, P2S5, LiI, and LiBr can be cited.

[0058] In the case of containing two or more halogens, the mixing ratio of the two or more halogens is not particularly limited. Similarly to the above, in the case of mixing and using LiI and LiBr, for example, by converting Li, P, S, and halogen (X) with Li2S, P2S5, and LiX, in cLiI･(1-c)LiBr, as c, from the aspect of the composition range capable of obtaining high ionic conductivity, it can be cited as 0.0 or more and 1.0 or less, and further can be cited as 0.25 or more and 0.67 or less.

[0059] The sulfide solid electrolyte used in the sulfide solid electrolyte particles of the present disclosure can be amorphous or can contain a crystal structure at least in part. The crystal state of the sulfide solid electrolyte in the sulfide solid electrolyte particles can be confirmed, for example, by performing powder X-ray diffraction measurement using CuKα rays on the sulfide solid electrolyte particles.

[0060] From the aspect of ionic conductivity, the sulfide solid electrolyte used in the sulfide solid electrolyte particles of the present disclosure preferably contains a crystal structure at least in part. For example, in powder X-ray diffraction using CuKα rays, it preferably has diffraction peaks at 2θ = 20.2 ± 0.5 degrees and 2θ = 23.6 ± 0.5 degrees.

[0061] The sulfide solid electrolyte used in the sulfide solid electrolyte particles of the present disclosure is a sulfide solid electrolyte containing Li, P, S, and a halogen as constituent elements, and other elements can also be included. As other elements, for example, in addition to oxygen, carbon, hydrogen, zirconium, etc. can also be listed.

[0062] The sulfide solid electrolyte used in the sulfide solid electrolyte particles of the present disclosure can be 100 mol% occupied by Li, P, S, and a halogen as constituent elements excluding oxygen.

[0063] The molar ratio of each element in the sulfide solid electrolyte can be controlled by adjusting the content of each element in the raw material. In addition, the molar ratio and composition of each element in the sulfide solid electrolyte can be measured, for example, by ICP emission spectrometry.

[0064] [Sulfide solid electrolyte particles]

[0065] As the shape of the sulfide solid electrolyte particles in the present disclosure, for example, a regular spherical shape or an ellipsoidal shape can be listed. In addition, when the sulfide solid electrolyte particles are in a particle shape, the average particle diameter can be, for example, in the range of 0.1 μm to 100 μm. The average particle diameter can be in the range of 0.5 μm to 20 μm, or can also be in the range of 0.5 μm to 10 μm.

[0066] The average particle diameter of the sulfide solid electrolyte particles can use, for example, a value measured based on image analysis using an electron microscope such as SEM.

[0067] The lower limit of the lithium ion conductivity of the sulfide solid electrolyte particles of the present disclosure at 25 °C is 2.1 mS / cm or more, preferably 2.4 mS / cm or more, and the upper limit is not particularly limited and can be 3.4 mS / cm or less.

[0068] [Manufacturing method of sulfide solid electrolyte particles]

[0069] The sulfide solid electrolyte particles in the present disclosure can be manufactured, for example, as follows.

[0070] From the aspect of solving the problems of the present disclosure, the method for manufacturing sulfide solid electrolyte particles in the present disclosure preferably includes: a step of preparing a sulfide solid electrolyte material; and a step of oxidizing the surface of the sulfide solid electrolyte material.

[0071] (Preparation of sulfide solid electrolyte material)

[0072] From the aspect of solving the problems of the present disclosure, the sulfide solid electrolyte material used in the sulfide solid electrolyte particles in the present disclosure is preferably manufactured from a raw material composition containing Li2S, P2S5, and LiX (where X is one or more atoms selected from the group consisting of halogens). It is preferable to make the raw material composition amorphous to form a sulfide solid electrolyte glass, and further, the sulfide solid electrolyte glass can be crystallized.

[0073] As a method for making the raw material composition amorphous, for example, mechanical grinding and melt quenching method can be cited, among which, mechanical grinding is preferred. This is because the treatment can be carried out at room temperature, and the manufacturing process can be simplified.

[0074] In addition, the melt quenching method has limitations in the reaction atmosphere and reaction vessel. On the other hand, mechanical grinding has the advantage of being able to easily synthesize a sulfide solid electrolyte glass with the desired composition.

[0075] Mechanical grinding can be dry mechanical grinding or wet mechanical grinding, and the latter is preferred. This is because it can prevent the raw material composition from sticking to the walls of the container, etc., and a sulfide solid electrolyte glass with higher amorphousness can be obtained.

[0076] Mechanical grinding is not particularly limited as long as it is a method of mixing while imparting mechanical energy to the raw material composition. For example, ball milling, vibration milling, turbo milling, mechanical alloying, disk milling, etc. can be cited, among which, ball milling is preferred, and planetary ball milling is particularly preferred. This is because the desired sulfide solid electrolyte glass can be obtained efficiently.

[0077] In addition, various conditions of mechanical grinding are set so that the desired sulfide solid electrolyte glass can be obtained. For example, in the case of using planetary ball milling, the raw material composition and grinding balls are added to the container and processed at a predetermined rotation speed and time. Generally, the greater the rotation speed, the faster the generation rate of the sulfide solid electrolyte glass, and the longer the processing time, the higher the conversion rate from the raw material composition to the sulfide solid electrolyte glass.

[0078] As the rotational speed of the chassis during planetary ball milling, for example, it is in the range of 200 rpm to 500 rpm, and particularly preferably in the range of 250 rpm to 400 rpm.

[0079] The treatment time during planetary ball milling is, for example, in the range of 1 hour to 100 hours, and particularly preferably in the range of 1 hour to 50 hours.

[0080] Examples of the materials for the container for ball milling and the grinding balls include ZrO2, Al2O3, etc.

[0081] The diameter of the grinding balls is, for example, in the range of 1 mm to 20 mm.

[0082] As the liquid for wet mechanical grinding, it is preferably a liquid that does not produce hydrogen sulfide in the reaction with the raw material composition. Hydrogen sulfide may be generated by the reaction of protons obtained from the dissociation of the molecules of the liquid with the raw material composition and the sulfide solid electrolyte glass. Therefore, the above liquid preferably has aproticity to the extent of not producing hydrogen sulfide. In addition, aprotic liquids can generally be roughly classified into polar aprotic liquids and nonpolar aprotic liquids.

[0083] There is no particular limitation on the polar aprotic liquid, and examples thereof include ketones such as acetone, nitriles such as acetonitrile, amides such as N,N-dimethylformamide (DMF), sulfoxides such as dimethyl sulfoxide (DMSO), etc.

[0084] In addition, examples of the nonpolar aprotic liquid include aliphatic hydrocarbons such as heptane; aromatic hydrocarbons such as benzene, toluene, and xylene; chain ethers such as diethyl ether and dimethyl ether; cyclic ethers such as tetrahydrofuran; halogenated alkanes such as chloroform, chloromethane, and dichloromethane; esters such as ethyl acetate; fluorine-containing compounds such as fluorobenzene, fluoroheptane, 2,3-dihydroperfluoropentane, and 1,1,2,2,3,3,4-heptafluorocyclopentane. It should be noted that the addition amount of the above liquid is not particularly limited and can be an amount sufficient to obtain the desired sulfide solid electrolyte.

[0085] In addition, the obtained sulfide solid electrolyte glass can be further ground to produce small-particle-size glass.

[0086] When producing small-particle-size glass, the obtained sulfide solid electrolyte glass and grinding balls are added to the container in the same manner as in the case of mechanical grinding, and processed at a predetermined rotational speed and time.

[0087] The diameter of the grinding balls when producing small-particle-size glass is, for example, in the range of 0.3 mm to 1.0 mm.

[0088] In the case of producing small-sized glass, it is also possible to list pulverization in the presence of a liquid for the wet mechanical grinding so as to make it wet mechanical grinding. When a compound containing an oxygen atom such as a chain ether such as diethyl ether or dimethyl ether is used in the liquid, it may become an oxidizing agent in the process of oxidizing the surface of the sulfide solid electrolyte material described later.

[0089] The obtained sulfide solid electrolyte glass or small-sized glass can be crystallized.

[0090] As the crystallization process, a process of crystallizing the obtained sulfide solid electrolyte glass or small-sized glass by heating it above the crystallization temperature of the glass can be listed.

[0091] This crystallization process can be carried out simultaneously with the process of oxidizing the surface of the sulfide solid electrolyte material described later.

[0092] (Surface oxidation of sulfide solid electrolyte material)

[0093] The process of oxidizing the surface of the sulfide solid electrolyte material (surface oxidation process) is as follows: The sulfide solid electrolyte material is brought into contact with an oxidizing agent to oxidize the surface of the sulfide solid electrolyte material and form an oxide layer.

[0094] The oxidizing agent used in this process is not particularly limited as long as it can oxidize the surface of the sulfide solid electrolyte material to form an oxide layer on the surface, and a gas can be used, for example. As the gas, an oxygen-containing gas can be listed. Specifically, air, pure oxygen, etc. can be listed. In addition, as the oxidizing agent, a compound containing an oxygen atom such as a chain ether for the wet mechanical grinding can be used.

[0095] The gas preferably has little water content. This is because a drying process described later is required in the case of containing moisture.

[0096] The surface oxidation method used in this process is not particularly limited as long as it can oxidize the surface of the sulfide solid electrolyte material to form an oxide layer, and a commonly used method can be used. Specifically, a method of holding the sulfide solid electrolyte material in a gas having a predetermined temperature and humidity for a predetermined time can be listed.

[0097] As the surface oxidation conditions such as the above temperature, the above humidity, and the above time, there is no particular limitation as long as they are conditions that can oxidize the surface of the sulfide solid electrolyte material to form an oxide layer. For example, in the case of using air as the oxidizing agent, the surface oxidation process and the drying process described later can be carried out in air as a preliminary experiment to determine the surface oxidation conditions such as the temperature, humidity, and time for forming the desired amount of the above oxide layer.

[0098] Among them, it is preferable from the aspect of solving the problems of the present disclosure and improving the ionic conductivity that there is a step of subjecting the obtained sulfide solid electrolyte glass or small particle size glass to oxidative crystallization by heating in the presence of the oxidant at a temperature above the crystallization temperature of the glass.

[0099] The crystallization temperature (Tc) of the sulfide solid electrolyte glass or small particle size glass can be measured by thermal analysis (DTA).

[0100] The heating temperature can be a temperature higher than the crystallization temperature (Tc) observed by thermal analysis of the sulfide solid electrolyte glass or small particle size glass, usually 195°C or higher, and 200°C or higher can be cited. On the other hand, the upper limit of the heating temperature is not particularly limited and can reach the crystallization temperature (Tc) + 20°C.

[0101] The heating time is not particularly limited as long as it is a time sufficient to obtain the desired crystallinity. For example, it is in the range of 1 minute to 24 hours, and within the range of 1 minute to 10 hours can be cited.

[0102] In addition, the heating is preferably carried out in an atmosphere containing a trace amount of oxygen as an oxidant and the rest being an inert gas such as argon or nitrogen. As the gas containing a trace amount of oxygen as an oxidant, for example, an inert gas containing 0.1% by volume or more and 2.0% by volume or less of oxygen can be cited.

[0103] The method of the heat treatment is not particularly limited, and for example, a method using a firing furnace can be cited.

[0104] The sulfide solid electrolyte obtained through the heating step can be completely crystallized by heat treatment, or can be incompletely crystallized and remain containing glass.

[0105] (Other steps)

[0106] As other steps, for example, a drying step can be further provided.

[0107] This drying step is a step of, after the surface oxidation step, removing moisture from the oxide layer formed on the surface of the sulfide solid electrolyte material by oxidation in the surface oxidation step to produce sulfide solid electrolyte particles having an oxide layer free of moisture.

[0108] The drying method used in this step is not particularly limited as long as it is a method capable of obtaining the above-mentioned moisture-free oxide layer, and a commonly used method can be used. Specifically, a method of drying the surface of the above-mentioned sulfide solid electrolyte material in a predetermined atmosphere, temperature, and time can be cited.

[0109] For example, as a preliminary experiment, the above-described surface oxidation process and drying process can be carried out, and drying conditions such as the atmosphere, temperature, and time for forming the desired amount of the above-described oxide layer can be determined.

[0110] The atmosphere during the above drying can be an atmosphere that can dry the oxide layer containing moisture to remove moisture and can form an oxide layer without moisture, and there is no particular limitation. Examples thereof include a vacuum atmosphere.

[0111] [Use of Sulfide Solid Electrolyte Particles]

[0112] As uses of the sulfide solid electrolyte particles of the present disclosure, for example, use in all-solid-state batteries can be cited. As types of all-solid-state batteries, all-solid-state lithium batteries, all-solid-state lithium-ion batteries, all-solid-state magnesium batteries, all-solid-state sodium batteries, and all-solid-state calcium batteries can be cited. Among them, all-solid-state lithium batteries, all-solid-state lithium-ion batteries, and all-solid-state sodium batteries are preferred, and all-solid-state lithium batteries and all-solid-state lithium-ion batteries are particularly preferred.

[0113] 2. All-Solid-State Battery

[0114] The all-solid-state battery of the present disclosure includes a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, and is characterized in that

[0115] at least any one of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer contains the sulfide solid electrolyte particles of the present disclosure.

[0116] Figure 2 FIG. is a schematic diagram showing an example of a power generation element of the all-solid-state battery of the present disclosure. Figure 2 The shown power generation element 100 has a positive electrode layer 11, a negative electrode layer 12, and a solid electrolyte layer 13 disposed between the positive electrode layer 11 and the negative electrode layer 12. The positive electrode layer 11 contains a positive electrode active material 20 and sulfide solid electrolyte particles 1, and they are uniformly mixed.

[0117] In Figure 2 when the all-solid-state battery is charged, for example, lithium ions are extracted from the positive electrode active material 20 of the positive electrode layer 11, and the lithium ions reach the negative electrode layer 12 along the sulfide solid electrolyte particles 1 and the solid electrolyte layer 13. On the contrary, when the all-solid-state battery is discharged, the lithium ions released from the negative electrode layer 12 reach the positive electrode active material 20 along the solid electrolyte layer 13. Usually, when the all-solid-state battery is charged and discharged, lithium ions move through the interface between the positive electrode active material and the sulfide solid electrolyte material. Therefore, in order to achieve high capacity and high output power of the all-solid-state battery, it is important to suppress an increase in interface resistance.

[0118] In Figure 2In this case, the surface of the sulfide solid electrolyte particles 1 is oxidized, suppressing the reaction at the interface between the positive electrode active material 20 and the sulfide solid electrolyte particles, and suppressing their respective chemical degradation. Therefore, the all-solid-state battery of the present disclosure can suppress the rate of increase in resistance after charge and discharge cycles.

[0119] It should be noted that in the above description, the case where the positive electrode layer contains the sulfide solid electrolyte particles of the present disclosure is exemplified, but the present disclosure is not limited to the above manner.

[0120] For example, when the solid electrolyte layer 13 contains the sulfide solid electrolyte particles 1, the surface of the sulfide solid electrolyte particles 1 is oxidized, suppressing the reaction at the interface between the active material contained in the positive electrode layer 11 or the negative electrode layer 12 and the sulfide solid electrolyte particles 1, and suppressing their respective chemical degradation. Therefore, the all-solid-state battery of the present disclosure can suppress the rate of increase in resistance after charge and discharge cycles.

[0121] In addition, when the negative electrode layer 12 contains a negative electrode active material and the sulfide solid electrolyte particles of the present disclosure, the surface of the sulfide solid electrolyte particles 1 is oxidized, suppressing the reaction at the interface between the negative electrode active material and the sulfide solid electrolyte particles, and suppressing their respective chemical degradation. Therefore, the all-solid-state battery of the present disclosure can suppress the rate of increase in resistance after charge and discharge cycles.

[0122] In the all-solid-state battery of the present disclosure, from the aspect of suppressing the rate of increase in resistance after charge and discharge cycles, it is particularly preferred that at least one of the positive electrode layer and the solid electrolyte layer contains the sulfide solid electrolyte particles, and it is preferred that the positive electrode layer contains the sulfide solid electrolyte particles.

[0123] In the all-solid-state battery of the present disclosure, from the aspect of suppressing the rate of increase in resistance after charge and discharge cycles, it may be a mode in which the positive electrode layer, the negative electrode layer, and the solid electrolyte layer all contain the sulfide solid electrolyte particles of the present disclosure.

[0124] Hereinafter, the all-solid-state battery of the present disclosure will be described for each component.

[0125] [Positive Electrode Layer]

[0126] The positive electrode layer contains at least a positive electrode active material and a solid electrolyte, and may contain a conductive material and a binder as needed.

[0127] When containing the sulfide solid electrolyte particles of the present disclosure as the solid electrolyte of the positive electrode layer, as the positive electrode active material, from the aspect of suppressing the rate of increase in resistance after charge and discharge cycles, it is preferred to use an oxide positive electrode active material.

[0128] As the oxide positive electrode active material, for example, those represented by the general formula Li x M y O z (where M is a transition metal element, x = 0.02 to 2.2, y = 1 to 2, z = 1.4 to 4) can be mentioned. In the above general formula, M can be at least one selected from the group consisting of Co, Mn, Ni, V, Fe, and Si, and can be at least one selected from the group consisting of Co, Ni, and Mn. As such an oxide positive electrode active material, specifically, LiCoO2, LiMnO2, LiNiO2, LiVO2, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiMn2O4, Li(Ni 0.5 Mn 1.5 )O4, Li2FeSiO4, Li2MnSiO4, etc. can be mentioned. In addition, as the positive electrode active material other than the above general formula Li x M y O z , olivine-type positive electrode active materials such as LiFePO4 and LiMnPO4 can be mentioned.

[0129] As the positive electrode active material in the positive electrode layer, conventionally known positive electrode active materials other than the oxide positive electrode active material can be used.

[0130] The shape of the positive electrode active material is not particularly limited, and particle shape, plate shape, etc. can be mentioned.

[0131] The content of the positive electrode active material in the positive electrode layer is not particularly limited, and for example, it can be in the range of 10% by mass to 99% by mass, or can be in the range of 20% by mass to 90% by mass, or can be in the range of 40% by mass to 85% by mass.

[0132] When the sulfide solid electrolyte particles of the present disclosure are contained as the solid electrolyte in the positive electrode layer, the content of the sulfide solid electrolyte particles of the present disclosure in the positive electrode layer is not particularly limited. For example, it can be in the range of 1% by mass to 80% by mass, among which, it can be in the range of 5% by mass to 70% by mass, and particularly can be in the range of 10% by mass to 50% by mass.

[0133] When the sulfide solid electrolyte particles of the present disclosure are not contained in the positive electrode layer, as the solid electrolyte, the solid electrolytes exemplified in the following solid electrolyte layer can be appropriately selected and used. The content of the solid electrolyte when the sulfide solid electrolyte particles of the present disclosure are not contained in the positive electrode layer can be the same as the content of the sulfide solid electrolyte particles.

[0134] Examples of the conductive material include carbon materials such as acetylene black and Ketjen black; fibrous carbon such as carbon fiber; and metal materials, etc.

[0135] The content of the conductive material in the positive electrode layer is not particularly limited, for example, it is in the range of 0 mass% to 10 mass%, and among them, it can also be in the range of 1 mass% to 5 mass%.

[0136] Examples of the binder are not particularly limited, and include butadiene rubber (BR), polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), etc.

[0137] The content of the binder in the positive electrode layer is not particularly limited, for example, it is in the range of 0 mass% to 20 mass%, and among them, it can be in the range of 0.1 mass% to 10 mass%.

[0138] The thickness of the positive electrode layer is not particularly limited, for example, it is 10 μm to 250 μm, and among them, it can be 20 μm to 200 μm.

[0139] [Negative electrode layer]

[0140] The negative electrode layer contains at least a negative electrode active material and a solid electrolyte, and contains a conductive material and a binder as needed.

[0141] When the sulfide solid electrolyte particles of the present disclosure are contained as the solid electrolyte of the negative electrode layer, as the negative electrode active material, from the aspect of suppressing the increase rate of the resistance after charge and discharge cycles, it is preferable to use an oxide negative electrode active material.

[0142] Examples of the oxide negative electrode active material include, for example, an active material having a spinel structure. Specifically, Li4Ti5O 12 , Li4Mn2O4, Li4Mn5O 12 etc.

[0143] As the negative electrode active material in the negative electrode layer, conventionally known negative electrode active materials other than the oxide negative electrode active material can be used. Examples of the conventionally known negative electrode active material include, for example, Li metal, graphite, Si metal, Si alloy, etc.

[0144] The shape of the negative electrode active material is not particularly limited, and examples include particulate shape, plate shape, etc.

[0145] The contents of the negative electrode active material, the sulfide solid electrolyte particles of the present disclosure, and the solid electrolyte in the negative electrode layer can be the same as the contents of the positive electrode active material, the sulfide solid electrolyte particles of the present disclosure, and the solid electrolyte in the positive electrode layer, respectively.

[0146] The conductive material and binder in the negative electrode layer, and their contents, can be the same as those in the positive electrode layer, including the conductive material, binder, and their contents.

[0147] [Solid electrolyte layer]

[0148] The solid electrolyte layer contains at least a solid electrolyte, and may also contain a binder or the like as needed.

[0149] Examples of the solid electrolyte used for the solid electrolyte layer include oxide-based solid electrolyte materials and sulfide-based solid electrolyte materials. Among them, considering the high lithium ion conductivity, sulfide solid electrolyte materials are preferred.

[0150] Considering the aspect of suppressing the increase rate of resistance after charge-discharge cycles, it is preferred to contain the sulfide solid electrolyte particles of the present disclosure as the solid electrolyte of the solid electrolyte layer. In this case, considering the aspect of suppressing the increase rate of resistance after charge-discharge cycles, it is preferred that at least one of the positive electrode layer and the negative electrode layer contains an oxide active material.

[0151] Examples of sulfide-based solid electrolyte materials different from the sulfide solid electrolyte particles of the present disclosure include, for example: Li2S-SiS2, LiI-Li2S-SiS2, LiI-Li2S-P2S5, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, LiI-Li2O-Li2S-P2S5, LiBr-LiI-Li2S-P2S5, Li2S-P2S5, etc.

[0152] Specifically, Li7P3S 11 , Li3PS4, Li8P2S9, Li 13 GeP3S 16 , Li 10 GeP2S 12 , 15LiBr･10LiI･75(0.75Li2S･0.25P2S5), 70(0.06Li2O･0.69Li2S･0.25P2S5)･30LiI, etc. It should be noted that the composition is indicated in moles.

[0153] As a sulfide-based solid electrolyte material different from the sulfide solid electrolyte particles of the present disclosure, sulfide solid electrolyte particles that have not undergone the process of surface oxidation and whose surface oxygen concentration does not meet the range of the sulfide solid electrolyte particles of the present disclosure can be used.

[0154] The solid electrolyte can be used alone or in combination of two or more.

[0155] The content of the solid electrolyte in the solid electrolyte layer is not particularly limited. For example, it can be 50% by mass or more, can be 100% by mass, can also be in the range of 70% to 99.99% by mass, or can be in the range of 90% to 99.9% by mass.

[0156] The binder that can be contained as needed can be the same as the binder in the positive electrode layer.

[0157] The content of the binder in the solid electrolyte layer is not particularly limited. For example, it is in the range of 0% to 20% by mass, and among them, it can also be in the range of 0.1% to 10% by mass.

[0158] Regarding the film thickness of the above solid electrolyte layer, there is no particular limitation, and a thickness that is the same as the thickness of the solid electrolyte film used in a normal all-solid-state lithium secondary battery can be used.

[0159] [Positive electrode current collector and negative electrode current collector]

[0160] Although not shown in Figure 2 , in the all-solid-state battery of the present disclosure, a positive electrode current collector and a negative electrode current collector are usually used. The positive electrode current collector collects the current of the above positive electrode layer. As the above positive electrode current collector, there is no particular limitation as long as it has the function of a positive electrode current collector. As the material of the above positive electrode current collector, there is no particular limitation as long as it has conductivity, and examples include SUS (stainless steel), aluminum, nickel, iron, titanium, copper, and carbon. The positive electrode current collector can be a dense metal current collector or a porous metal current collector.

[0161] In addition, the negative electrode current collector collects the current of the above negative electrode layer. As the above negative electrode current collector, there is no particular limitation as long as it has the function of a negative electrode current collector. As the material of the above negative electrode current collector, it can be the same material as the positive electrode current collector.

[0162] In addition, the above positive electrode current collector and the above negative electrode current collector used in the present disclosure can also serve as the function of the battery case. Specifically, there can be cited cases such as preparing a battery case made of SUS and using a part of it as the current collecting part.

[0163] [Other components]

[0164] The all-solid-state battery optionally includes an outer package that houses the positive electrode, negative electrode, and solid electrolyte layer.

[0165] Regarding the shape of the outer package, there is no particular limitation, and examples include a laminated type.

[0166] The material of the outer package is not particularly limited as long as it is stable to the electrolyte, and examples include resins such as polypropylene, polyethylene, and acrylic resins.

[0167] Examples of all-solid-state batteries include all-solid-state lithium batteries, all-solid-state lithium-ion batteries, all-solid-state magnesium batteries, all-solid-state sodium batteries, and all-solid-state calcium batteries. Among them, all-solid-state lithium batteries, all-solid-state lithium-ion batteries, and all-solid-state sodium batteries are preferred, and all-solid-state lithium batteries and all-solid-state lithium-ion batteries are particularly preferred.

[0168] Examples of the shape of the all-solid-state battery include, for example, coin type, laminate type, cylindrical type, and square type.

[0169] In addition, the method for manufacturing the all-solid-state battery of the present disclosure is not particularly limited as long as it can obtain the above all-solid-state battery, and the same method as the general method for manufacturing an all-solid-state battery can be used. As an example of the method for manufacturing the all-solid-state battery, the following methods can be cited: by sequentially pressing the material constituting the positive electrode layer, the material constituting the solid electrolyte layer, and the material constituting the negative electrode layer to produce a power generation element, and housing the power generation element inside a battery case and caulking the battery case.

[0170] [Examples]

[0171] (Example 1)

[0172] (1) Manufacture of sulfide solid electrolyte particles

[0173] 0.5503 g of Li2S (Furuuchi Chemical Co., Ltd.), 0.8874 g of P2S5 (Aldrich), 0.2850 g of LiI (High Purity Chemical Research Institute Co., Ltd.), and 0.2773 g of LiBr (High Purity Chemical Research Institute Co., Ltd.) were put into a zirconia pot (45 mL) equipped with 5 mm diameter zirconia balls, and then 4 g of dehydrated heptane (Kanto Chemical Co., Inc.) was added and the lid was closed. It was placed in a planetary ball mill (manufactured by Fritsch, P-7) and mechanically milled for 20 hours to obtain a sulfide solid electrolyte glass.

[0174] 2 g of the sulfide solid electrolyte glass was put into a zirconia pot equipped with 0.3 mm diameter zirconia balls again, 2 g of dibutyl ether (Kishida Chemical Co., Ltd.) and 6 g of dehydrated heptane were added, and stirred for 20 hours to produce small-sized glass.

[0175] While flowing the obtained small-sized glass with 100 vol% Ar, it was heated at a temperature above the crystallization temperature (200 °C) for 3 hours to be fired, and sulfide solid electrolyte particles 1 of Example 1 were obtained. In this example, dibutyl ether during the production of small-sized glass becomes an oxidant during firing.

[0176] The oxygen / sulfur element ratio at the surface of the obtained sulfide solid electrolyte particles 1 and at a position 30 nm away from the surface is measured by XPS measurement described below. The results are shown in Table 1.

[0177] It should be noted that the obtained sulfide solid electrolyte particles 1 are subjected to powder X-ray diffraction measurement described below, and as a result, diffraction peaks are observed at 2θ = 20.1 degrees and 2θ = 23.7 degrees.

[0178] (2) Fabrication of all-solid-state lithium-ion secondary battery

[0179] (2-1) Fabrication of positive electrode

[0180] As the positive electrode active material, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (manufactured by Nichia Chemical Industries, Ltd.) was used. The surface treatment of LiNbO3 was performed on this positive electrode active material. 1.862 g of this positive electrode active material, 0.028 g of VGCF (manufactured by Showa Denko K.K.), which is carbon as a conductive material, 0.295 g of the sulfide solid electrolyte particles 1 as a solid electrolyte, 0.279 g of PVDF (manufactured by Kureha Corporation), and 0.999 g of butyl butyrate (manufactured by Nacalai Tesque, Inc.) were weighed respectively, and the material obtained by mixing using an ultrasonic homogenizer (UH-50, manufactured by SMT Co., Ltd.) was used as the positive electrode mixture material. This positive electrode mixture material was coated on an Al foil (positive electrode current collector), and dried on a hot plate at 100 °C for 30 minutes, thereby fabricating a positive electrode sheet, and the sheet obtained by punching with a 1 cm 2 punching machine was used as the positive electrode layer.

[0181] (2-2) Fabrication of negative electrode

[0182] 0.800 g of silicon metal (manufactured by Elkem) as the negative electrode active material, 0.621 g of the sulfide solid electrolyte particles 1 as a solid electrolyte, 0.320 g of PVDF (manufactured by Kureha Corporation), and 1.643 g of butyl butyrate (manufactured by Nacalai Tesque, Inc.) were weighed respectively, and the material obtained by mixing using an ultrasonic homogenizer (UH-50, manufactured by SMT Co., Ltd.) was used as the negative electrode mixture material. This negative electrode mixture material was coated on a Cu foil (negative electrode current collector), and dried on a hot plate at 100 °C for 30 minutes, thereby fabricating a negative electrode sheet, and the sheet obtained by punching with a 1 cm 2 punching machine was used as the negative electrode layer.

[0183] (2-3) Fabrication of solid electrolyte layer

[0184] Weigh 0.400 g of the sulfide solid electrolyte particles 1 serving as the solid electrolyte, 0.032 g of amino-modified hydrogenated butadiene rubber (manufactured by JSR Corporation), 0.715 g of dehydrated heptane, and 0.050 g of butyl butyrate respectively. Coat the material obtained by mixing using an ultrasonic homogenizer on an Al foil and dry it on a hot plate at 100 °C for 30 minutes, thereby fabricating a solid electrolyte sheet. The sheet obtained by punching the solid electrolyte sheet using a punching machine with a size of 1 cm 2 and also the sheet with the Al foil peeled off are used as the solid electrolyte layer. Three such solid electrolyte layers are fabricated.

[0185] (2-4) Fabrication of All-Solid-State Lithium-Ion Secondary Battery

[0186] On a MACOR glass-ceramic mold with a size of 1 cm 2 , bond one such positive electrode layer, three such solid electrolyte layers, and one such negative electrode layer. While clamping with SUS pins, press them under a pressure of 6 t / cm 2 (≈588 MPa), thereby fabricating the all-solid-state lithium-ion secondary battery of Example 1.

[0187] (Example 2)

[0188] In the fabrication of the sulfide solid electrolyte particles of Example 1, set the firing atmosphere of the small-sized glass to 99.5 vol% Ar and 0.5 vol% O₂ gas. Except for this, fabricate the sulfide solid electrolyte particles 2 of Example 2 in the same manner as in Example 1.

[0189] In the fabrication of the all-solid-state lithium-ion secondary battery of Example 1, use the sulfide solid electrolyte particles 2 of Example 2 to replace the sulfide solid electrolyte particles 1 of Example 1. Except for this, fabricate the all-solid-state lithium-ion secondary battery in the same manner as in Example 1.

[0190] (Example 3)

[0191] In the fabrication of the sulfide solid electrolyte particles of Example 1, set the firing atmosphere of the small-sized glass to 99 vol% Ar and 1 vol% O₂ gas. Except for this, fabricate the sulfide solid electrolyte particles 3 of Example 3 in the same manner as in Example 1.

[0192] In the fabrication of the all-solid-state lithium-ion secondary battery of Example 1, use the sulfide solid electrolyte particles 3 of Example 3 to replace the sulfide solid electrolyte particles 1 of Example 1. Except for this, fabricate the all-solid-state lithium-ion secondary battery in the same manner as in Example 1.

[0193] (Comparative Example 1)

[0194] In the production of the sulfide solid electrolyte particles of Example 1, the firing atmosphere of the small particle size glass was set to 98 vol% Ar and 2 vol% O2 gas, and other than this, the comparative sulfide solid electrolyte particles 1 of Comparative Example 1 were produced in the same manner as in Example 1.

[0195] In the production of the all-solid-state lithium ion secondary battery of Example 1, the comparative sulfide solid electrolyte particles 1 of Comparative Example 1 were used instead of the sulfide solid electrolyte particles 1 of Example 1, and other than this, the all-solid-state lithium ion secondary battery was produced in the same manner as in Example 1.

[0196] [Evaluation]

[0197] (1) Oxygen / sulfur element ratio measurement

[0198] The oxygen / sulfur element ratio on the surface of each sulfide solid electrolyte particle obtained in the examples and comparative examples and the oxygen / sulfur element ratio at a position 30 nm from the surface (converted at the SiO2 sputtering rate) were measured by XPS, respectively.

[0199] The conditions for XPS measurement are as follows.

[0200] XPS measurement device: Manufactured by ULVAC, ULVAC-PHI

[0201] <Measurement conditions for XPS>

[0202] Measurement light source: Al (monochromator)

[0203] Analysis area: 200 μmφ

[0204] Pass energy: (wide scan) 187 eV, (narrow scan) 46 eV

[0205] Energy step: (wide scan) 0.8 eV, (narrow scan) 0.1 eV

[0206] <Sputtering conditions>

[0207] Acceleration voltage, current: 3.0 kV, 20 mA

[0208] AMPL: (3 mm × 3 mm)

[0209] Sputtering rate: 3.9 nm / minute (converted at SiO2)

[0210] The elemental distribution of each element was obtained in the depth direction, and the O / S element ratio of the outermost layer and the O / S element ratio inside when etched by 30 nm were calculated. Regarding the 30 nm depth, it was calculated from the sputtering rate of 3.9 nm / minute converted at SiO2.

[0211] (2) X-ray crystal diffraction measurement

[0212] The XRD spectra of the sulfide solid electrolyte particles obtained in the examples and comparative examples were determined by powder X-ray diffraction using CuKα rays based on a powder X-ray diffractometer (trade name: RINT-UltimaIII, manufactured by Rigaku Corporation). It should be noted that the measurement was carried out in the range of a scanning rate of 1° / min and a diffraction angle of 2θ = 10° to 40°.

[0213] (3) Ionic conductivity

[0214] 100 mg of each of the sulfide solid electrolyte particles obtained in the examples and comparative examples was weighed, and pre-pressed at a pressure of 7 MPa using a pellet press to produce solid electrolyte pellets. Subsequently, carbon-coated foils (carbon coat foils) with a thickness of 21 μm were provided on both sides of the solid electrolyte pellets. The two sides of the solid electrolyte pellets held by the carbon-coated foils were further held by pins made of stainless steel (SUS), and in this state, cold pressing was performed at a pressure of 40 MPa and bolt tightening was performed at a torque of 6 N to produce a unit for measuring ionic conductivity.

[0215] The unit for measuring ionic conductivity was placed in an AC impedance measuring device (trade name: Solatron1260, manufactured by Solartron), and AC impedance measurement (25 °C) was performed under the conditions of applying a voltage of 10 mV and a measurement frequency range of 0.01 MHz to 1 MHz.

[0216] The ionic conductivity was calculated from the resistance obtained by AC impedance measurement and the pellet thickness.

[0217] (4) Rate of increase in resistance after charge and discharge cycles

[0218] Each all-solid-state battery obtained in the examples and comparative examples was charged and discharged at 25 °C for 1 cycle with a constant current-constant voltage of 1 / 3C, 4.55V - 3V, and then charged and discharged 5 cycles with 1 / 3C, 4.37V - 3V. The resistance of the battery thereafter was determined and taken as the initial resistance. Subsequently, at 60 °C, a cycle test was performed at 2C, 4.37V - 3V up to 300 cycles, and the battery resistance thereafter was taken as the battery resistance after cycling. The percentage of the battery resistance after cycling with the initial resistance set to 100% was calculated as the rate of increase in resistance.

[0219] Rate of increase in resistance after cycling (%) = (battery resistance after cycling) / (initial resistance) × 100

[0220] [Results]

[0221] Table 1 below is a table comparing the ionic conductivities of Examples 1 to 3 and Comparative Example 1, and the rate of increase in resistance after charge-discharge cycles, together with the oxygen / sulfur element ratios at the surface of the sulfide solid electrolyte particles and at positions 30 nm from the surface (in terms of the SiO2 sputtering rate).

[0222]

[0223] As shown in Table 1, in Comparative Example 1 using sulfide solid electrolyte particles with an oxygen / sulfur element ratio at the surface and at positions 30 nm from the surface higher than the oxygen / sulfur element ratio specified in the present disclosure, the ionic conductivity decreased extremely. When contained in an all-solid-state battery as in the examples, the resistance was too high to evaluate the rate of increase in resistance after cycling.

[0224] In contrast, in Examples 1 to 3 using sulfide solid electrolyte particles containing a sulfide solid electrolyte having Li, P, S, and a halogen as constituent elements, with an oxygen / sulfur element ratio at the surface measured by XPS of 0.79 or more and 1.25 or less, and an oxygen / sulfur element ratio at positions 30 nm from the surface of 0.58 or less, it was confirmed that the decrease in ionic conductivity was suppressed and sufficient ionic conductivity was achieved.

[0225] In addition, in the all-solid-state lithium-ion secondary batteries of Examples 1 to 3 using sulfide solid electrolyte particles containing a sulfide solid electrolyte having Li, P, S, and a halogen as constituent elements, with an oxygen / sulfur element ratio at the surface measured by XPS of 0.79 or more and 1.25 or less, and an oxygen / sulfur element ratio at positions 30 nm from the surface of 0.58 or less, it was confirmed that the rate of increase in resistance after charge-discharge cycles could be suppressed.

Claims

1. A sulfide solid electrolyte particle for an all-solid-state battery, containing a sulfide solid electrolyte comprising Li, P, S, and a halogen as constituent elements, and the oxygen / sulfur element ratio on the surface of the sulfide solid electrolyte particle for the all-solid-state battery measured by XPS is 0.79 or more and 1.25 or less, and the oxygen / sulfur element ratio at a position 30 nm from the surface (converted at the SiO2 sputtering rate) is 0.58 or less.

2. The sulfide solid electrolyte particle for an all-solid-state battery according to claim 1, wherein, The sulfide solid electrolyte particles for all-solid-state batteries contain a sulfide solid electrolyte including Li, P, S, I, and Br as constituent elements.

3. An all-solid-state battery, comprising a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, wherein, At least one of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer contains the sulfide solid electrolyte particles for all-solid-state batteries according to claim 1 or 2.

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