Sulfide solid electrolyte material, method for manufacturing the same, and battery containing the same

Abstract

To provide a sulfide solid electrolyte material that is based on resource-rich elements, has a lithium ion conductivity that is approximately equal to or greater than that of conventional materials, is relatively inexpensive, and has a crystal structure, a method for producing the same, and a battery containing the same.SOLUTION: Provided are a sulfide solid electrolyte material which contains a sulfide composition represented by a composition formula Li2-4x-ySi1+x-yPyS3 and is characterized by -0.040≤x≤0.095 and 0.036≤y≤0.192, a method for producing the same, and a battery containing the same.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a novel sulfide solid electrolyte material, a method for producing the same, and a battery containing the same. [Background technology]

[0002] In recent years, with the rapid proliferation of information-related devices and communication equipment such as personal computers, video cameras, and mobile phones, the development of batteries used as their power sources has become increasingly important. Furthermore, the automotive industry is also developing high-output, high-capacity batteries for electric vehicles and hybrid vehicles. Currently, among various types of batteries, lithium-ion rechargeable batteries are attracting attention due to their high energy density.

[0003] Currently available lithium-ion rechargeable batteries use electrolytes containing flammable organic solvents, requiring the installation of safety devices to suppress temperature rise during short circuits and improvements in structure and materials to prevent short circuits. In contrast, lithium-ion rechargeable batteries that use a solid electrolyte instead of liquid electrolytes, thus eliminating the use of flammable organic solvents, are thought to offer advantages in terms of simplified safety devices, manufacturing costs, and productivity. However, all-solid-state lithium-ion rechargeable batteries currently have a lower energy density compared to liquid-based batteries.

[0004] Sulfide solid electrolyte materials are known as solid electrolyte materials used in all-solid-state lithium-ion secondary batteries. For example, Li-Si-S sulfide-based solid electrolytes have been reported (see, for example, Non-Patent Documents 1 and 2). The ionic conductivity of these crystalline sulfides is 2 × 10⁻⁶. -6 ~4×10 -5 It's approximately S / cm.

[0005] Patent Document 1 is a document relating to a glassy lithium cation conductor Li2SiS3, and its ionic conductivity is 0.73 × 10⁻⁶. -4 S / cm, or 0.97 × 10 -4 It has been disclosed that the ratio is S / cm.

[0006] Furthermore, Non-Patent Document 3 describes Li containing relatively expensive Ge. 10 GeP2S 12 This document concerns (which may be referred to as "LGPS-based sulfide solid electrolyte," "LGPS," etc., below), and its ionic conductivity is 12 × 10⁻⁶. -3 It exhibits a high ionic conductivity of S / cm, comparable to that of an electrolyte. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Special Publication No. 60-501731 [Non-patent literature]

[0008] [Non-Patent Document 1] Byung Tae Ahn, Robert A. Huggins, Synthesis and Li Conductivities of Li2SiS3 and Li4SiS4, Mat. Res. Bull., 24, 889(1989) [Non-Patent Document 2] Byung Tae Ahn, Robert A. Huggins, Phase behavior and conductivity of Li2SiS3 composition, Solid State Ionics, 46, 237(1991) [Non-Patent Document 3] Noriaki Kamaya et al., A lithium superionic conductor, Nature Materials, Advanced online publication, 31 July 2011, DOI:10.1038 / NMAT3066 [Overview of the project] [Problems that the invention aims to solve]

[0009] Solid electrolyte materials having higher ionic conductivity are demanded for achieving higher energy density and higher input / output density of all-solid-state lithium ion secondary batteries. Inorganic solid electrolytes include amorphous materials and crystalline materials. This distinction can be easily confirmed by X-ray diffraction measurement. Since an amorphous material has a random crystal structure, no characteristic diffraction peak is observed in X-ray diffraction measurement, and it is difficult to specify the crystal structure of the amorphous material. On the other hand, for a crystalline material, diffraction peaks derived from the crystal structure specific to the material are observed. Therefore, abundant information on the crystal structure such as lattice constant can be obtained, and analysis of the ion conduction path thereof is also possible. In addition, obtaining such a large amount of information is also advantageous from the aspect of quality control during mass production of the material. For this reason, as an inorganic solid electrolyte material, crystalline materials have more advantages than amorphous materials. Furthermore, it is also required that constituent elements used in the material are abundantly present in nature, and raw material compounds thereof are inexpensive. Therefore, an object of the present invention is to provide a sulfide solid electrolyte material that is based on elements with abundant resource reserves, has lithium ion conductivity substantially equal to or higher than that of conventional materials, and has a crystal structure. In such material development, it is also an object of the present invention to provide a method for producing the same and a battery using the same. [Means for Solving the Problem]

[0010] In order to solve the above problems, the following means are provided according to the present invention.

[0011] [1] Composition formula Li 2-4x-y Si 1+x-y P y S3, comprising a sulfide composition represented by the formula, wherein -0.040≦x≦0.095, 0.036≦y≦0.192, and the sulfide solid electrolyte material has a crystal structure. [2] The sulfide solid electrolyte material according to [1], characterized in that, in powder X-ray diffraction measurements using Cu-Kα rays with an X-ray wavelength of 1.5418 Å, it has peaks at at least the diffraction angles (2θ) of 15.43°±0.50°, 15.62°±0.50°, 19.49°±0.50°, 20.98°±0.50°, 24.94°±0.50°, 26.99°±0.50°, 27.68°±0.50°, 30.47°±0.50°, 31.04°±0.50°, and 39.55°±0.50°. [3] The ionic conductivity at 25°C is 4.0 × 10⁻⁶. -5 The sulfide solid electrolyte material according to [1] or [2], characterized in that it is S / cm or higher. [4] A method for producing a sulfide solid electrolyte according to any one of items [1] to [3], comprising: an ion conductive material synthesis step of synthesizing an amorphous ion conductive material by mechanical milling; and a heating step of obtaining the sulfide solid electrolyte material by heating the amorphous ion conductive material. [5] The method for producing a sulfide solid electrolyte according to [4], characterized in that the heating step is in the range of 300°C to 500°C. [6] A battery comprising a positive electrode active material layer containing a positive electrode active material, a negative electrode active material layer containing a negative electrode active material, and an electrolyte layer formed between the positive electrode active material layer and the negative electrode active material layer, wherein at least one of the positive electrode active material layer, the negative electrode active material layer, and the electrolyte layer contains the sulfide solid electrolyte material described in any one of [1] to [3]. [Effects of the Invention]

[0012] According to one embodiment of the present invention, a novel sulfide solid electrolyte material containing abundant silicon (Si) as a basic constituent element and having good lithium-ion conductivity, and a method for producing the same can be provided. Furthermore, by using the sulfide solid electrolyte material of this embodiment as a battery material or the like, a battery with high ionic conductivity can be obtained. [Brief explanation of the drawing]

[0013] [Figure 1] This is a ternary composition diagram of the Li2S-SiS2-P2S5 system, showing the compositional range of the sulfide-based solid electrolyte of the present invention. [Figure 2] This is an X-ray diffraction pattern of a sulfide solid electrolyte material, which is one embodiment of the present invention, and conventionally known Equilibrium-Li2SiS3 and Metastable-Li2SiS3. [Figure 3] This diagram schematically shows an outline of a method for producing a sulfide solid electrolyte material, which is one embodiment of the present invention. [Figure 4] This is an example of differential scanning calorimetry. [Figure 5] This is an X-ray diffraction pattern of sulfide solid electrolyte materials obtained by heating amorphous precursors at various heating temperatures (sometimes called heat treatment temperatures). [Figure 6] This is an X-ray diffraction pattern of a sulfide solid electrolyte material obtained at a heating temperature of 460°C (733K) or higher (sometimes referred to as the heat treatment temperature). [Figure 7] This is an X-ray diffraction pattern of a sulfide solid electrolyte material, which is one embodiment of the present invention. [Figure 8] This shows the measurement results of the ionic conductivity of a sulfide solid electrolyte material, which is one embodiment of the present invention. [Figure 9] This shows the results of a constant current charge-discharge test of a sulfide solid electrolyte material, which is one embodiment of the present invention. [Modes for carrying out the invention]

[0014] The sulfide solid electrolyte material of the present invention will be described in detail below, but the present invention is not limited to the embodiments described below.

[0015] First, the sulfide solid electrolyte material of the present invention will be described. The inventors of this invention have found that, based on conventionally known Equilibrium-Li2SiS3 (Non-Patent Literature 1) and Metastable-Li2SiS3 (Non-Patent Literature 2), a sulfide solid electrolyte material with superior lithium ion conductivity can be obtained by reviewing the manufacturing conditions and composition ratio, and that this sulfide solid electrolyte material has a novel crystal structure that has not been previously confirmed. As a result of these studies, the present invention was completed.

[0016] (composition) The sulfide solid electrolyte material according to the present invention has the composition formula Li 2-4x-y Si 1+x-y P y It contains a sulfide composition represented by S3, with -0.040 ≤ x ≤ 0.095 and 0.036 ≤ y ≤ 0.192.

[0017] The sulfide-based solid electrolyte of the present invention will be explained with reference to the ternary composition diagram of Li2S-SiS2-P2S5 in Figure 1. The base material for the sulfide solid electrolyte material of the present invention is the conventionally known Equilibrium-Li2SiS3 (Non-Patent Literature 1) or Metastable-Li2SiS3 (Non-Patent Literature 2). In this composition, Li2SiS3 is the midpoint of the left side of the triangle in the ternary composition diagram of Figure 1, or in other words, it is the midpoint between the top vertex (Li2S) and the left vertex (SiS2) of the triangle, and has a composition of Li2S:SiS2 = 50:50 (molar ratio). However, in this case, Li4SiS4 impurities tend to precipitate, so a SiS2-rich composition makes it easier to obtain a single phase. Specifically, it is shifted to the left vertex (SiS2) of the triangle in the ternary composition diagram. Composition formula Li 2-4x-y Si 1+x-y P y In S3, increase x.

[0018] Furthermore, shifting the composition to the right vertex (P2S5) of the triangle in the ternary composition diagram increases the proportion of P2S5. In this case, crystallinity improves, contributing to improved ionic conductivity. However, if the proportion of P2S5 is too high, the Li4P2S6 impurity phase, which has low ionic conductivity, precipitates, thus reducing ionic conductivity. Also, phosphorus-based sulfide solid electrolyte materials, such as Li3PS4 and Li7PS6, are known, but phosphorus (P), one of their constituent elements, is present in the Earth's crust at a mass ratio of only 0.1% (11th place), while silicon (Si) is the second most abundant element in the Earth's crust (mass ratio of 27%), making it an advantageous element from a resource perspective. Taking these factors into consideration, the composition formula Li 2-4x-y Si 1+x-y P y In S3, y is defined within an appropriate range.

[0019] Based on the above guidelines, Li 2-4x-y Si 1+x-y P y In S3, -0.040 ≤ x ≤ 0.095 and 0.036 ≤ y ≤ 0.192. In the enlarged view of the target composition region in Figure 1, the region drawn by connecting #1 → #7 → #8 → #5 → #6 corresponds to this composition range. The inventors have discovered that a sulfide-based solid electrolyte with a novel crystal structure can be obtained within this composition range.

[0020] (X-ray diffraction measurement) In one embodiment of the present invention, the sulfide solid electrolyte material may have peaks at diffraction angles (2θ) of at least 15.43°±0.50°, 15.62°±0.50°, 19.49°±0.50°, 20.98°±0.50°, 24.94°±0.50°, 26.99°±0.50°, 27.68°±0.50°, 30.47°±0.50°, 31.04°±0.50°, and 39.55°±0.50° in X-ray diffraction measurements using CuKα rays with an X-ray wavelength of 1.5418 Å. The X-ray diffraction peaks are determined by the crystal structure.

[0021] Figure 2 shows the X-ray diffraction peaks of a sulfide solid electrolyte material, which is one embodiment of the present invention, alongside those of conventionally known Equilibrium-Li2SiS3 and Metastable-Li2SiS3, displayed side by side for comparison. In Figure 2, n-Li2SiS3 refers to the sulfide solid electrolyte material of one embodiment of the present invention, m-Li2SiS3 refers to Metastable-Li2SiS3, and e-Li2SiS3 refers to Equilibrium-Li2SiS3. The chart on the far right of Figure 2 is an enlarged view of the area where 2θ is 26-28°, and it is confirmed that the sulfide solid electrolyte material of one embodiment of the present invention has a different peak than the conventionally known Equilibrium-Li2SiS3 and Metastable-Li2SiS3, indicating that it has a novel crystal structure. Furthermore, since the crystal structure is thought to be related to ionic conductivity, the novel crystal structure can achieve ionic conductivity exceeding that of the conventionally known Equilibrium-Li2SiS3 and Metastable-Li2SiS3.

[0022] (Ionic conductivity) In one embodiment of the present invention, the sulfide solid electrolyte material has an ionic conductivity of 4.0 × 10⁻¹⁰ at 25°C, when the powdered sulfide solid electrolyte material is measured by AC impedance method. -5 A conductivity of S / cm or higher can be obtained. High ionic conductivity is preferable, and in one embodiment of the present invention, the ionic conductivity of the sulfide solid electrolyte material is preferably 7.0 × 10⁻⁶. -5 It may be S / cm or more, and more preferably 1.0 × 10 -4 The conductivity may be greater than or equal to S / cm. The conventionally known ionic conductivity of Equilibrium-Li2SiS3 and Metastable-Li2SiS3 is 4 × 10⁻⁶, respectively. -6 S / cm, 2×10 -5 The sulfide solid electrolyte material, which is one embodiment of the present invention, has better ionic conductivity than those with an S / cm rating.

[0023] (Manufacturing method) One embodiment of the present invention, a sulfide solid electrolyte material, is not limited to the means of production, but can be produced by the following means. Figure 3 schematically shows an overview of the production method. One embodiment of the present invention, a method for producing a solid electrolyte material, may be characterized by comprising an ion conductive material synthesis step of synthesizing an amorphous ion conductive material by mechanical milling, and a heating step of obtaining the sulfide solid electrolyte material by heating the amorphous ion conductive material. A detailed explanation follows below.

[0024] First, Li, Si, P, and S elements are weighed to the desired composition. Sulfides of each element, such as Li2S, SiS2, and P2S5, may be used as raw materials. Furthermore, it is preferable to pre-grind coarse raw materials. As shown in Figure 3, Li2S, SiS2, and P2S5 are weighed to the desired composition and pre-mixed using an agate mortar before mechanical milling.

[0025] (Ion-conducting material synthesis process) Amorphous ion-conducting materials are synthesized by mechanically milling the supplied raw materials.

[0026] Mechanical milling is a method of grinding a sample while applying mechanical energy. In this embodiment, an amorphous ion-conducting material is synthesized by applying mechanical energy to the raw material. Examples of such mechanical milling methods include ball mills, vibratory mills, turbo mills, mechanofusion mills, and disc mills, with vibratory mills and ball mills being preferred.

[0027] The conditions for the ball mill are not particularly limited as long as it can produce amorphous ion-conducting material. Generally, the higher the rotational speed, the faster the rate of ion-conducting material formation, and the longer the processing time, the higher the conversion rate from the raw material composition to ion-conducting material. When performing planetary ball milling, the rotational speed of the base plate is preferably in the range of 200 rpm to 500 rpm, and more preferably in the range of 300 rpm to 400 rpm.

[0028] The conditions for the vibratory mill are not particularly limited as long as it can produce amorphous ion-conducting material. The vibration amplitude of the vibratory mill is preferably in the range of 5 mm to 15 mm, and more preferably in the range of 6 mm to 10 mm. The vibration frequency of the vibratory mill is preferably in the range of 500 rpm to 2000 rpm, and more preferably in the range of 1000 rpm to 1800 rpm. The packing density of the sample in the vibratory mill is preferably in the range of 1 volume% to 80 volume%, more preferably in the range of 5 volume% to 60 volume%, and particularly preferably in the range of 10 volume% to 50 volume%. Furthermore, it is preferable to use a vibrator (for example, an alumina vibrator) in the vibratory mill.

[0029] The processing time for mechanical milling may be 30 hours or more in order to synthesize amorphous ion-conducting material. If the processing time is less than 30 hours, the uniformity of each element in the obtained amorphous ion-conducting material (hereinafter sometimes referred to as the precursor) may decrease, leading to the precipitation of impurity phases during calcination, a decrease in the crystallinity of the calcined product, and / or a decrease in ionic conductivity. There is no particular upper limit to the processing time, but since the effects of improving uniformity, crystallinity, and ionic conductivity will saturate, it may be 96 hours or less, or even 72 hours or less.

[0030] (Heating process) By heating (calcining) an amorphous ion-conducting material (precursor), a sulfide solid electrolyte material having the crystalline structure of the embodiment of the present invention can be obtained.

[0031] It is preferable to pelletize the precursor, vacuum seal it in a quartz tube, and heat it. This prevents oxidation of the precursor and prevents some of the supplied raw materials from volatilizing and changing the composition.

[0032] A heating temperature of 300°C or higher is preferable. A temperature of 300°C or higher facilitates the precipitation of the novel crystalline phase. A temperature of 350°C or higher is also preferable. Figure 4 shows an example of differential scanning calorimetry of an amorphous ion-conducting material (precursor). A glass transition (Tg) is observed around 300°C, and a crystallization peak (Tc) is observed around 350°C. This confirms that the crystalline phase precipitates at temperatures above 300°C.

[0033] From the viewpoint of enhancing crystallinity, it is preferable to raise the upper limit of the heating temperature, and it is preferable to heat up to a temperature range of 450°C ± 50°C. On the other hand, if the heating temperature is 500°C or higher, equilibrium-Li2SiS3 and Li4SiS4 may precipitate, which may reduce the ionic conductivity.

[0034] Figure 5 shows the X-ray diffraction patterns of sulfide solid electrolyte materials obtained at various heating temperatures (sometimes called heat treatment temperatures), allowing us to observe the changes in the crystalline structure depending on the heating temperature (heat treatment temperature). The sample heated at 275°C remained amorphous, the same as before heat treatment, but a new crystalline phase peak (●) can be observed in the sample heated at 300°C.

[0035] Figure 6 is an X-ray diffraction pattern of a sulfide solid electrolyte material, one embodiment of the present invention, fired at 460°C (733K) or higher. When fired at 500°C (773K), the Equilibrium phase and Li4SiS4 begin to appear, and at 600°C (873K), it can be confirmed that the structure has completely changed to the Equilibrium phase. Conventional Equilibrium-Li2SiS3 (Non-Patent Literature 1) and Metastable-Li2SiS3 (Non-Patent Literature 2) are obtained by heat treatment at 1000°C to create a melt, then holding it at 720°C for 12 hours and allowing it to cool naturally, while the latter is obtained by cooling the melt to room temperature over 5 to 6 hours.

[0036] Based on the above, in one embodiment of the present invention, the heating step may be in the range of 300°C to 500°C. Within this temperature range, a novel sulfide solid electrolyte material having a crystalline structure, which is one embodiment of the present invention, can be suitably obtained without containing Equilibrium-Li2SiS3, Metastable-Li2SiS3, and Li4SiS4.

[0037] In the series of steps included in the above manufacturing method, it is preferable to work in a glove box or the like under an inert gas atmosphere such as argon in order to prevent hydrolysis of the raw material powder, precursor powder, and the obtained sulfide solid electrolyte material due to moisture in the air.

[0038] (battery) Since the sulfide solid electrolyte material of one embodiment of the present invention can be ionic conductive, it can be used in any application requiring ionic conductivity. In particular, the sulfide solid electrolyte material of the present application is preferably used in batteries, because it can greatly contribute to improving the performance of batteries.

[0039] A battery according to one embodiment of the present invention comprises a positive electrode active material layer containing a positive electrode active material, a negative electrode active material layer containing a negative electrode active material, and an electrolyte layer formed between the positive electrode active material layer and the negative electrode active material layer, wherein at least one of the positive electrode active material layer, the negative electrode active material layer, and the electrolyte layer contains a sulfide solid electrolyte as described above in the embodiment of the present invention.

[0040] As described above, the sulfide solid electrolyte material of one embodiment of the present invention can have good ionic conductivity. Therefore, by using the above-described sulfide solid electrolyte material in the battery of this embodiment, a solid battery exhibiting good performance can be obtained.

[0041] Furthermore, naturally, considering that the material will actually be used as a battery, it is desirable that even a solid electrolyte material with confirmed ionic conductivity be able to be charged and discharged stably when incorporated into a battery and that it exhibits minimal performance degradation (reduction in charge / discharge capacity). In one embodiment of the present invention, a battery using a sulfide solid electrolyte material operates stably and exhibits minimal reduction in charge capacity even when a charge / discharge test simulating actual operation is performed, which is preferable.

[0042] The positive electrode active material, negative electrode active material, and electrolyte layer are not particularly limited, and those commonly used in batteries can be used as long as they do not affect the effects of the present invention. [Examples]

[0043] The present invention will be described in more detail below with reference to examples. Note that the following examples are not intended to limit the present invention.

[0044] (Sample preparation) In a glove box under an argon atmosphere, the starting materials Li2S, SiS2, and P2S5 were weighed to the desired composition, ground and mixed using an agate mortar, and then mechanically milled in a ball mill for 40 hours to synthesize an amorphous material (precursor). The sample was placed in a pelletizer, and a pressure of 20 MPa was applied to the pelletizer using a uniaxial press to form a φ13 mm pellet. This pellet was sealed in a carbon-coated quartz tube under a near-vacuum of 10 Pa. The quartz tube containing the pellet was then heated to 300-500°C over 3 hours, held for 8 hours, and then allowed to cool naturally. Furthermore, for subsequent evaluation, the particle size was adjusted by thoroughly grinding in an agate mortar. The composition of the synthesized sample is shown in Table 1, corresponding to #1 to #9 shown in the enlarged view of the target composition region in Figure 1.

[0045] [Table 1]

[0046] The following measurements and evaluations were performed on the obtained samples.

[0047] (Powder X-ray diffraction measurement) To identify the crystalline phases contained in the prepared samples, powder X-ray diffraction measurements were performed using the Ultima-IV powder X-ray diffractometer (manufactured by Rigaku Corporation) and the Smart Lab (manufactured by Rigaku Corporation). Cu-Kα rays with an X-ray wavelength of 1.5418 angstroms were used for the powder X-ray diffraction measurements. Powder X-ray diffraction measurements were performed in the diffraction angle (2θ) range of 10 to 50° in 0.01° steps.

[0048] (Measurement of ionic conductivity) Ionic conductivity was measured using a powder compaction cell with stainless steel jigs (pins) installed on both the top and bottom of a resin cylinder. After placing the sample inside the cylinder with pins installed on one side of the powder compaction cell, the sample was flattened by inserting pins from the other side, and then pre-molded by applying a pressure of 5 MPa. After dispersing gold powder on both sides of the pre-molded pellet, electrodes were formed on both sides of the pellet by applying a pressure of 15 MPa to create a sample for measurement. An impedance / gain phase analyzer Solatron 1260 (manufactured by Solartron Corporation) was used to measure the ionic conductivity of the sample. AC impedance measurements were performed at a measurement frequency range of 1 Hz to 3 MHz, an applied voltage of 10 mV, and a measurement temperature of 25°C, and the ionic conductivity of the sample was calculated.

[0049] (Constant current charge / discharge test) In the charge-discharge test, the sulfide solid electrolyte material #1 (Li) obtained in the examples was used as the lithium-ion conductive solid electrolyte. 1.82 SiP 0.036 S3) is placed in a compacted cell, and one side of it is coated with LiNbO3 as the positive electrode active material. 0.6 Co 0.2 Mn 0.2 The positive electrode active material layer contains O2, and the other side has Li4Ti5O as the negative electrode active material. 12 A negative electrode active material layer containing [the specified material] was stacked to construct an all-solid-state lithium-ion secondary battery. These batteries underwent charge-discharge testing at 30°C and 1 / 10C (=18mA / g).

[0050] [evaluation] (X-ray diffraction measurement) X-ray diffraction (XRD) measurements were performed using the sulfide solid electrolyte materials obtained above. The results are shown in Figure 7. For sulfide solid electrolyte materials (#1~9) within the composition range of the present invention, peaks (●) indicating a novel crystal structure were confirmed.

[0051] (Measurement of Li-ion conductivity) The sulfide solid electrolyte material #1 (Li) obtained above 1.82 SiP 0.036 The results of measuring the ionic conductivity of the compressed powder of S3) by AC impedance method are shown on the left of Figure 8. Example of the present invention: Sulfide solid electrolyte material #1 (Li 1.82 SiP 0.036 When S3) is heated (calcined) at 460°C, it exhibits an ionic conductivity (6.5 × 10⁻¹⁰) that is more than an order of magnitude higher than that of conventionally known Li2SiS3. -4 The ionic conductivity (S / cm@25℃) was confirmed. Table 1 shows the ionic conductivity of samples #1 to #9 after heating (calcination) at 300℃ and / or 500℃.

[0052] (Constant current charge / discharge test) In the charge-discharge test, the sulfide solid electrolyte material obtained above was used as the separator layer between the positive electrode active material layer and the negative electrode active material layer to construct an all-solid-state lithium-ion secondary battery. The charge-discharge curve when this battery was charged and discharged is shown in Figure 9. It was confirmed that the all-solid-state lithium-ion secondary battery using the sulfide solid electrolyte material according to the present invention was capable of charging and discharging and operated without problems. In other words, it was confirmed that the electrolyte material of the present invention has high electrochemical stability and functions as a solid electrolyte for all-solid-state batteries.

Claims

1. Composition formula Li ２－４ｘ－ｙ Si １＋ｘ－ｙ P ｙ S ３ It contains a sulfide composition represented by -0.040 ≤ x ≤ 0.095, 0.036 ≤ y ≤ 0.192, A sulfide solid electrolyte material characterized by having a crystal structure having peaks at at least the following diffraction angles (2θ): 15.43°±0.50°, 15.62°±0.50°, 19.49°±0.50°, 20.98°±0.50°, 24.94°±0.50°, 26.99°±0.50°, 27.68°±0.50°, 30.47°±0.50°, 31.04°±0.50°, and 39.55°±0.50°, as measured by powder X-ray diffraction using Cu-Kα rays with an X-ray wavelength of 1.5418 Å.

2. The ionic conductivity at 25°C is 4.0 × 10⁻⁶. －５ The sulfide solid electrolyte material according to claim 1, characterized in that it is S / cm or higher.

3. A method for producing a sulfide solid electrolyte material according to claim 1 or 2, comprising: an ion conductive material synthesis step of synthesizing an amorphous ion conductive material by mechanical milling; and a heating step of obtaining the sulfide solid electrolyte material by heating the amorphous ion conductive material.

4. The method for producing a sulfide solid electrolyte material according to claim 3, characterized in that the heating step is within the range of 300°C to 500°C.

5. A battery comprising a positive electrode active material layer containing a positive electrode active material, a negative electrode active material layer containing a negative electrode active material, and an electrolyte layer formed between the positive electrode active material layer and the negative electrode active material layer, wherein at least one of the positive electrode active material layer, the negative electrode active material layer, and the electrolyte layer contains the sulfide solid electrolyte material described in claim 1 or 2.

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