Sulfide solid electrolyte, battery, and method for producing sulfide solid electrolyte

Abstract

The present invention relates to a sulfide solid electrolyte, a battery, and a method for manufacturing a sulfide solid electrolyte. The main object is to provide a sulfide solid electrolyte with high ionic conductivity. The present disclosure solves the above problems by providing the following sulfide solid electrolyte, which has an LGPS-type crystal phase containing Li element, Sn element, P element, and S element. The above sulfide solid electrolyte has a composition represented by Li 4‑x Sn 1‑x P x S4 (0.67 < x < 0.76). In the above sulfide solid electrolyte, in 31 P-NMR measurement, it has a first peak with a vertex at a position of 77 ppm ± 1 ppm and a second peak with a vertex at a position of 93 ppm ± 1 ppm. When the sum of the areas of all the peaks obtained in the above 31 P-NMR measurement is set as S1, and the sum of the areas of the above first peak and the above second peak is set as S2, the ratio (S2 / S1) of S2 to S1 is 92.0% or more.

Description

Technical Field

[0001] The present disclosure relates to sulfide solid electrolytes. Background Art

[0002] All-solid batteries are batteries that have a solid electrolyte layer between a positive electrode layer and a negative electrode layer, and have the advantage of being easy to simplify safety devices compared to liquid batteries that have an electrolyte solution containing a flammable organic solvent. Sulfide solid electrolytes are known as solid electrolytes used in all-solid batteries.

[0003] For example, Patent Document 1 discloses a sulfide solid electrolyte containing an M1 element (e.g., Li), an M2 element (e.g., Ge and P), and an S element, and having a peak at a predetermined position in X-ray diffraction measurement. In addition, Patent Document 2 discloses a sulfide solid electrolyte containing an M1 element (e.g., Li), an M2 element (e.g., Sn and P), and an S element, and having a peak at a predetermined position in X-ray diffraction measurement.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent No. 5527673

[0007] Patent Document 2: International Publication No. 2013 / 118722 Summary of the invention

[0008] Problems to be solved by the invention

[0009] The sulfide solid electrolytes disclosed in Patent Documents 1 and 2 have a so-called LGPS type crystal phase. In addition, for example, in Patent Document 2, as Examples 5-1 to 5-8, a sulfide solid electrolyte having a Li 4-x Sn 1-x P x A sulfide solid electrolyte having a composition represented by S4 and having a crystal phase A (LGPS type crystal phase). In particular, paragraph

[0110] of Patent Document 2 discloses that the sulfide solid electrolytes obtained in Examples 5-3 to 5-8 have a crystal phase A (LGPS type crystal phase) and do not have a crystal phase B (a crystal phase having lower ion conductivity than the LGPS type crystal phase).

[0010] In the XRD diagrams described in Figures 12(c) to (h) of Patent Document 2, peaks appear at the same position, so it can be judged that the sulfide solid electrolytes obtained in Examples 5-3 to 5-8 have crystalline phase A (LGPS type crystalline phase) as a single phase. The inventors of the present application prepared a plurality of such sulfide solid electrolytes that can be judged as having crystalline phase A as a single phase using XRD diagrams, and obtained a new insight that there is a deviation in ionic conductivity. Therefore, the composition of these sulfide solid electrolytes was further analyzed in detail, and the following insight was obtained: these sulfide solid electrolytes contain a small amount of impurity components, and the impurity components affect the ionic conductivity.

[0011] The present disclosure has been made in view of the above-mentioned actual situation, and a main object of the present disclosure is to provide a sulfide solid electrolyte having high ion conductivity.

[0012] Means for solving problems

[0013] The present invention provides a sulfide solid electrolyte, which is a sulfide solid electrolyte having an LGPS type crystal phase containing Li element, Sn element, P element and S element, wherein the sulfide solid electrolyte has Li 4-x Sn 1-x P x The composition represented by S4 (0.67<x<0.76), the above-mentioned sulfide solid electrolyte 31 In the P-NMR measurement, there is a first peak having a vertex at 77 ppm ± 1 ppm and a second peak having a vertex at 93 ppm ± 1 ppm. 31 When the total area of ​​all peaks obtained in P-NMR measurement is S1 and the total area of ​​the first peak and the second peak is S2, the ratio of S2 to S1 (S2 / S1) is 92.0% or more.

[0014] According to the present disclosure, since S2 / S1 is large, the sulfide solid electrolyte has high ion conductivity.

[0015] In the above disclosure, the above sulfide solid electrolyte is 31 In the P-NMR measurement, at least one of the third peak having a vertex at 87 ppm ± 1 ppm and the fourth peak having a vertex at 89 ppm ± 1 ppm is obtained. 31 When the total area of ​​all peaks obtained by P-NMR measurement is defined as S1 and the total area of ​​the third peak and the fourth peak is defined as S3, the ratio of S3 to S1 (S3 / S1) can be 6.0% or less.

[0016] In the above disclosure, the above sulfide solid electrolyte is 31In the P-NMR measurement, there is a fifth peak with a vertex at 68 ppm ± 1 ppm. 31 When the area of ​​all peaks obtained by P-NMR measurement is defined as S1 and the area of ​​the fifth peak is defined as S4, the ratio of S4 to S1 (S4 / S1) can be 0.5% or less.

[0017] In the above disclosure, the above S2 / S1 may be 95.0% or more.

[0018] In the above disclosure, the above x may satisfy 0.67<x≤0.74.

[0019] In the above disclosure, the above x may satisfy 0.67<x≤0.72.

[0020] In the above disclosure, the ion conductivity of the above sulfide solid electrolyte at 25° C. may be 5.25 mS / cm or more.

[0021] In addition, the present disclosure provides a battery comprising a positive electrode layer containing a positive electrode active material, a negative electrode layer containing a negative electrode active material, and an electrolyte layer arranged between the above-mentioned positive electrode layer and the above-mentioned negative electrode layer, wherein at least one of the above-mentioned positive electrode layer, the above-mentioned negative electrode layer and the above-mentioned electrolyte layer contains the above-mentioned sulfide solid electrolyte.

[0022] According to the present disclosure, a battery having good discharge characteristics is achieved by using the above-mentioned sulfide solid electrolyte.

[0023] In addition, the present disclosure provides a method for producing a sulfide solid electrolyte, which is a method for producing a sulfide solid electrolyte having an LGPS type crystal phase containing Li element, Sn element, P element and S element, comprising: an amorphization step, wherein an ion conductive material is obtained by amorphizing a raw material composition; and a heating step, wherein the ion conductive material is heated in an inert gas flow to obtain the sulfide solid electrolyte, wherein the sulfide solid electrolyte is heated in an inert gas flow. 31 In the P-NMR measurement, as the peaks of the LGPS type crystal phase, there are a first peak having a vertex at a position of 77ppm±1ppm and a second peak having a vertex at a position of 93ppm±1ppm. 31 When the total area of ​​all peaks obtained in P-NMR measurement is S1 and the total area of ​​the first peak and the second peak is S2, the ratio of S2 to S1 (S2 / S1) is 92.0% or more.

[0024] According to the present disclosure, a sulfide solid electrolyte having a large S2 / S1 ratio and high ion conductivity is obtained by heating in an inert gas flow.

[0025] Effects of the Invention

[0026] The present disclosure exerts an effect of being able to provide a sulfide solid electrolyte with high ion conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is an explanatory diagram for explaining the peak separation of the NMR chart in the present disclosure.

[0028] Figure 2 is a perspective view illustrating the LSnPS crystal phase in the present disclosure.

[0029] Figure 3 This is a schematic cross-sectional view illustrating a battery in the present disclosure.

[0030] Figure 4 This is a flow chart illustrating a method for producing a sulfide solid electrolyte in the present disclosure.

[0031] Figure 5 These are the results of XRD measurement of the sulfide solid electrolytes obtained in Examples 1 to 6 and Comparative Examples 1 to 5.

[0032] Figure 6 For the sulfide solid electrolytes obtained in Examples 1 to 6 and Comparative Examples 1 to 5 31 Results of P-NMR measurement.

[0033] Figure 7 It is a graph showing the relationship between S2 / S1 and ion conductivity in the sulfide solid electrolytes obtained in Examples 1 to 6 and Comparative Examples 1 to 5.

[0034] Figure 8 Yes Figure 7 A magnified image of a portion of the image.

[0035] Description of Reference Numerals

[0036] 1… Positive electrode layer

[0037] 2…Negative electrode layer

[0038] 3…Electrolyte layer

[0039] 4…Positive electrode collector

[0040] 5…Negative electrode collector

[0041] 6…Outer packaging

[0042] 10…Battery DETAILED DESCRIPTION

[0043] Hereinafter, the sulfide solid electrolyte, battery, and method for producing the sulfide solid electrolyte in the present disclosure are described in detail. In the present disclosure, the LGPS type crystal phase containing Li element, Sn element, P element, and S element is sometimes referred to as LSnPS crystal phase.

[0044] A. Sulfide solid electrolyte

[0045] The sulfide solid electrolyte in the present disclosure is a sulfide solid electrolyte having an LGPS type crystal phase containing Li element, Sn element, P element and S element, wherein the sulfide solid electrolyte has a Li 4-x Sn 1-x P x The composition represented by S4 (0.67<x<0.76), the above-mentioned sulfide solid electrolyte 31 In the P-NMR measurement, there is a first peak having a vertex at 77 ppm ± 1 ppm and a second peak having a vertex at 93 ppm ± 1 ppm. 31 When the total area of ​​all peaks obtained in P-NMR measurement is S1 and the total area of ​​the first peak and the second peak is S2, the ratio of S2 to S1 (S2 / S1) is 92.0% or more.

[0046] According to the present disclosure, since S2 / S1 is large, it becomes a sulfide solid electrolyte with high ion conductivity. As mentioned above, Patent Document 2 discloses a sulfide solid electrolyte that is a single-phase material determined to be an LGPS type crystal phase based on XRD measurement. The inventors of the present application have conducted a detailed analysis of the composition of such a sulfide solid electrolyte. Specifically, using 31 The P-NMR measurement analyzed the state of P (phosphorus) in the sulfide solid electrolyte. As a result, the following insights were obtained: the sulfide solid electrolyte, which was judged to be a single-phase material, slightly contained impurity components. As described in the examples described later, the impurity components are estimated to be Li3PS4 and Li3PS2O2. It is estimated that Li3PS2O2 is a compound generated by the reaction of the elements contained in the raw material composition with the oxygen element that is inevitably mixed.

[0047] The inventors of the present application who obtained the above-mentioned insights have tried to reduce the proportion of impurity components. However, as described in Patent Document 2, even if the amorphized ion conductive material is heated in a sealed state, it is difficult to reduce the proportion of impurity components, that is, it is difficult to increase the proportion of LGPS type crystal phase. The inventors of the present application have repeatedly conducted in-depth studies, and as a result, the desired sulfide solid electrolyte can be obtained by using the impurity components as a management value and heating the amorphized ion conductive material in an inert gas flow.

[0048] The sulfide solid electrolyte in the present disclosure is 31 In the P-NMR measurement, there is a first peak having a vertex at 77 ppm±1 ppm and a second peak having a vertex at 93 ppm±1 ppm. Both the first peak and the second peak correspond to the peak of PS4 in the LSnPS crystal phase.

[0049] The sulfide solid electrolyte in the present disclosure is 31 In the P-NMR measurement, at least one of a third peak having a vertex at 87ppm±1ppm and a fourth peak having a vertex at 89ppm±1ppm may be provided. The third peak and the fourth peak are both equivalent to the peak of PS4 in a phase other than the LSnPS crystal phase (most likely Li3PS4). The sulfide solid electrolyte may or may not have the third peak. In addition, the sulfide solid electrolyte may or may not have the fourth peak.

[0050] The sulfide solid electrolyte in the present disclosure is 31 In the P-NMR measurement, there may be a fifth peak with a vertex at 68 ppm ± 1 ppm. The fifth peak corresponds to the peak of the anion part (most likely PS2O2) in the phase having Li, P, S and O (most likely Li3PS2O2).

[0051] In this disclosure, 31 The NMR chart obtained by P-NMR measurement was subjected to peak separation. At this time, fitting was performed so that the error was minimized. Figure 1 is an explanatory diagram for explaining the peak separation of the NMR graph in the present disclosure. 31 P-NMR measurement, for example Figure 1 (a) shows the NMR graph. Figure 1 In (a), the first peak and the second peak are observed as large peaks. Figure 1 When the NMR chart shown in (a) is separated by taking into account the above-mentioned peaks, the peaks are Figure 1 Each peak is identified as shown in (b).

[0052] Here, 31 The total area of ​​all peaks obtained in the P-NMR measurement is defined as S1. In addition, the total area of ​​the first peak and the second peak is defined as S2, the total area of ​​the third peak and the fourth peak is defined as S3, and the area of ​​the fifth peak is defined as S4.

[0053] It is preferred that the ratio of S2 to S1 (S2 / S1) is large. This is because the proportion of the LGPS type crystal phase is large. S2 / S1 is usually above 92.0%, can be above 93.0%, can be above 94.0%, or can be above 95.0%. In addition, it is preferred that the ratio of S3 to S1 (S3 / S1) is small. This is because the proportion of the impurity component is small. S3 / S1 is, for example, 7.5% or less, can be 7.0% or less, can be 6.5% or less, can be 6.0% or less, or can be 3.5% or less. In addition, it is preferred that the ratio of S4 to S1 (S4 / S1) is small. This is because the proportion of the impurity component is small. S4 / S1 is, for example, 0.5% or less, can be 0.4% or less. Similarly, it is preferred that the ratio of S4 to S2 (S4 / S2) is small. This is because the proportion of the impurity component is small. S4 / S2 is, for example, 0.5% or less, or may be 0.4% or less.

[0054] The sulfide solid electrolyte in the present disclosure has an LGPS type crystal phase (LSnPS crystal phase) containing Li element, Sn element, P element, and S element. Figure 2 is a perspective view illustrating the LSnPS crystal phase in the present disclosure. Figure 2 The LSnPS crystal phase shown has an octahedral O composed of Li and S elements, a a The tetrahedron T1 composed of elements and S elements and the tetrahedron composed of M b The tetrahedron T2 is composed of M and S elements. The tetrahedron T1 and the octahedron O share edges, and the tetrahedron T2 and the octahedron O share vertices. a Elements and M b At least one of the elements includes Sn. a Elements and M b At least one of the elements includes the element P. Typically, the space group classification of the LSnPS crystal phase is P42 / nmc(137).

[0055] The LSnPS crystal phase in the present disclosure is observed to have a peak at a specified position in the X-ray diffraction measurement using CuKα rays. As the peak position of the LSnPS crystal phase, for example, 2θ=17.38°, 20.18°, 20.44°, 23.56°, 23.96°, 24.93°, 26.96°, 29.07°, 29.58°, 31.71°, 32.66°, and 33.39° can be cited. In particular, the LSnPS crystal phase has characteristic peaks at 2θ=20.18°, 20.44°, 26.96°, and 29.58°. In addition, the above-mentioned peak position, for example, the lattice changes slightly due to the material composition, and sometimes moves slightly back and forth. Therefore, the above-mentioned peak position can move back and forth in the range of ±0.50°, can move back and forth in the range of ±0.30°, and can move back and forth in the range of ±0.10°.

[0056] The sulfide solid electrolyte disclosed in the present invention has a Li 4-x Sn 1-x P x S4 (0.67 < x < 0.76) represents the composition. 4-x Sn 1-x P x S4 is equivalent to the tie line composition of Li4SnS4 and xLi3PS4. 4-x Sn 1-x P x S4 is equivalent to (1-x)Li4SnS4-xLi3PS4 in composition. In addition, if y=x / (1-x), then Li 4-x Sn 1-x P x S4 is equivalent to Li4SnS4-yLi3PS4 in composition. It should be noted that Li4SnS4 is equivalent to 2Li2S-1SnS2 in composition, and Li3PS4 is equivalent to 3Li2S-1P2S5 in composition.

[0057] Li 4-x Sn 1-x P xThe x in S4 is usually greater than 0.67 (= 2 / 3). x = 0.67 (y = 2) corresponds to the stoichiometric composition of the LSnPS crystal phase in the present disclosure. When y in Li4SnS4-yLi3PS4 is greater than 2, it becomes a composition that easily produces Li3PS4 as an impurity component. Even with such a composition, S2 / S1 can be increased by adopting, for example, a manufacturing method described later. x can be greater than 0.68, or greater than 0.69, or greater than 0.70, or greater than 0.71. On the other hand, x is, for example, less than 0.76, or less than 0.74, or less than 0.72. In addition, the range of x may also be a range other than 0.73 (i.e., greater than 0.725 and less than 0.734).

[0058] The sulfide solid electrolyte in the present disclosure preferably has high Li ion conductivity. The ion conductivity (25°C) of the sulfide solid electrolyte is, for example, 5.0 mS / cm or more, 5.25 mS / cm or more, or 5.3 mS / cm or more. The ion conductivity can be obtained by an AC impedance method. In addition, as a shape of the sulfide solid electrolyte, for example, a particle shape can be cited. The average particle size (D 50 ) is, for example, 0.1 μm or more and 50 μm or less. In addition, the sulfide solid electrolyte can be used for any application requiring ion conductivity. Among them, the sulfide solid electrolyte is preferably used for batteries.

[0059] B.Battery

[0060] Figure 3 This is a schematic cross-sectional view illustrating a battery in the present disclosure. Figure 3 The battery 10 in the embodiment includes: a positive electrode layer 1 containing a positive electrode active material, a negative electrode layer 2 containing a negative electrode active material, an electrolyte layer 3 disposed between the positive electrode layer 1 and the negative electrode layer 2, a positive electrode collector 4 for collecting current from the positive electrode layer 1, a negative electrode collector 5 for collecting current from the negative electrode layer 2, and an outer package 6 for housing these components. In the present disclosure, at least one of the positive electrode layer 1, the negative electrode layer 2, and the electrolyte layer 3 contains the sulfide solid electrolyte described in the above-mentioned "A. Sulfide solid electrolyte".

[0061] According to the present disclosure, a battery having good discharge characteristics is achieved by using the above-mentioned sulfide solid electrolyte.

[0062] 1. Positive electrode layer

[0063] The positive electrode layer in the present disclosure contains at least a positive electrode active material. The positive electrode layer may contain at least one of a solid electrolyte, a conductive material and a binder. In particular, the positive electrode layer preferably contains the above-mentioned sulfide solid electrolyte as a solid electrolyte. The proportion of the sulfide solid electrolyte in the positive electrode layer is, for example, 5% by volume or more, 10% by volume or more, or 20% by volume or more. On the other hand, the proportion of the sulfide solid electrolyte in the positive electrode layer is, for example, 60% by volume or less.

[0064] Examples of positive electrode active materials include LiCoO2, LiMnO2, LiNiO2, LiVO2, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 and other rock salt layered active materials, LiMn2O4, Li4Ti5O 12 、Li(Ni 0.5 Mn 1.5 )O4 and other spinel active materials, LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4 and other olivine active materials. The surface of the positive electrode active material can be coated with a Li ion conductive oxide such as LiNbO3. The thickness of the Li ion conductive oxide is, for example, not less than 1 nm and not more than 30 nm.

[0065] As the conductive material, for example, acetylene black (AB), Ketjen black (KB) and other particulate carbon materials; carbon fiber, carbon nanotube (CNT), carbon nanofiber (CNF) and other fibrous carbon materials can be cited. As the binder, for example, fluorine-based binders such as polyvinylidene fluoride (PVDF) can be cited. The thickness of the positive electrode layer is, for example, 0.1 μm or more and 1000 μm or less.

[0066] 2. Negative electrode layer

[0067] The negative electrode layer in the present disclosure contains at least a negative electrode active material. The negative electrode layer may contain at least one of a solid electrolyte, a conductive material, and a binder. In particular, the negative electrode layer preferably contains the above-mentioned sulfide solid electrolyte as a solid electrolyte. The proportion of the sulfide solid electrolyte in the negative electrode layer is, for example, 5% by volume or more, 10% by volume or more, or 20% by volume or more. On the other hand, the proportion of the sulfide solid electrolyte in the negative electrode layer is, for example, 60% by volume or less.

[0068] Examples of the negative electrode active material include Li-based active materials such as metal lithium and lithium alloys; carbon-based active materials such as graphite and hard carbon; oxide-based active materials such as lithium titanate; and Si-based active materials such as Si single substance, Si alloys, and silicon oxide. The conductive material and binder used in the negative electrode layer are the same as those used in the positive electrode layer. The thickness of the negative electrode layer is, for example, not less than 0.1 μm and not more than 1000 μm.

[0069] 3. Electrolyte layer

[0070] The electrolyte layer in the present disclosure is arranged between the positive electrode layer and the negative electrode layer, and contains an electrolyte. The electrolyte used for the electrolyte layer can be a solid electrolyte or a liquid electrolyte. Among them, the electrolyte layer is preferably a solid electrolyte layer containing a solid electrolyte. It should be noted that a battery with a solid electrolyte layer is also called an all-solid-state battery. The solid electrolyte layer preferably contains the above-mentioned sulfide solid electrolyte. The proportion of the sulfide solid electrolyte in the solid electrolyte layer is, for example, more than 50% by volume, can be more than 70% by volume, or can be more than 90% by volume. The thickness of the electrolyte layer is, for example, more than 0.1 μm and less than 1000 μm.

[0071] 4. Battery

[0072] The battery in the present disclosure may have a positive electrode collector and a negative electrode collector. Examples of materials for the positive electrode collector include SUS, aluminum, nickel, iron, titanium, and carbon. On the other hand, examples of materials for the negative electrode collector include SUS, copper, nickel, and carbon. Examples of outer packaging include a laminated outer packaging and a shell-type outer packaging.

[0073] The battery in the present disclosure is typically a lithium ion secondary battery. The purpose of the battery is not particularly limited, and for example, a power source for vehicles such as a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), an electric vehicle (BEV), a gasoline vehicle, and a diesel vehicle can be cited. It is particularly preferably used as a driving power source for a hybrid electric vehicle, a plug-in hybrid electric vehicle, or an electric vehicle. In addition, the all-solid-state battery in the present disclosure can be used as a power source for a mobile body (for example, a railway, a ship, an airplane) other than a vehicle, and can also be used as a power source for electrical products such as an information processing device.

[0074] C. Method for producing sulfide solid electrolyte

[0075] Figure 4 is a flow chart illustrating a method for producing a sulfide solid electrolyte in the present disclosure. Figure 4 In the process, first, a raw material composition is prepared by mixing Li2S, P2S5 and SnS2. Then, the raw material composition is amorphized by, for example, a ball mill, thereby obtaining an ion conductive material (amorphization step). Next, the obtained ion conductive material is heated in an inert gas flow (heating step). Thus, a sulfide solid electrolyte is obtained. The S2 / S1 of the obtained sulfide solid electrolyte is greater than a specified value.

[0076] According to the present disclosure, a sulfide solid electrolyte having a large S2 / S1 ratio is obtained by heating in an inert gas flow.

[0077] 1. Amorphization process

[0078] The amorphization step in the present disclosure is a step of obtaining an ion conductive material by amorphizing the raw material composition.

[0079] The raw material composition contains Li element, Sn element, P element and S element. The raw material composition is preferably a mixture containing a Li source, a Sn source, a P source and an S source. As a Li source, for example, a sulfide containing Li can be mentioned. As a sulfide containing Li, for example, Li2S can be mentioned. As a Sn source, for example, Sn simple substance and a sulfide containing Sn can be listed. As a sulfide containing Sn, for example, SnS2 can be listed. As a P source, for example, P simple substance and a sulfide containing P can be listed. As a sulfide containing P, for example, P2S5 can be listed. As an S source, for example, S simple substance, a sulfide containing Li, a sulfide containing Sn, and a sulfide containing P can be listed.

[0080] The raw material composition may have, for example, Li 4-z Sn 1-z P z The composition represented by S4 (0.67<z<0.76). z may be 0.68 or more, 0.69 or more, 0.70 or more, or 0.71 or more. On the other hand, z may be 0.74 or less, or 0.72 or less.

[0081] The method for amorphizing the raw material composition is not particularly limited, and examples thereof include mechanical grinding and melt quenching. In the mechanical grinding method, the raw material composition is pulverized while mechanical energy is applied. Examples of mechanical grinding include ball milling, vibration milling, turbine milling, and disc milling. The conditions for amorphization are appropriately set so as to obtain the desired ion conductive material.

[0082] When planetary ball milling is performed, the platen rotation speed is, for example, more than 200 rpm and less than 600 rpm, or more than 300 rpm and less than 500 rpm. The processing time of planetary ball milling is, for example, more than 1 hour and less than 100 hours, and can be more than 5 hours and less than 70 hours. In addition, when vibration milling is performed, the vibration amplitude is, for example, more than 5 mm and less than 15 mm, and can be more than 6 mm and less than 10 mm. The vibration frequency of the vibration mill is, for example, more than 500 rpm and less than 2000 rpm, and can be more than 1000 rpm and less than 1800 rpm. In addition, it is preferred to use a vibrator (for example, a vibrator made of aluminum oxide) in the vibration mill. The processing time of the vibration mill is, for example, more than 1 hour and less than 100 hours, and can be more than 5 hours and less than 70 hours.

[0083] The crystallinity of the raw material in the ion conductive material is generally lower than the crystallinity of the raw material in the raw material composition. The crystallinity of the raw material can be confirmed by X-ray diffraction (XRD) measurement. For example, in the case where the raw material composition contains Li2S as a raw material, the ion conductive material may or may not have a peak of Li2S in the XRD measurement. In the former case, the peak intensity of Li2S in the ion conductive material is generally smaller than the peak intensity of Li2S in the raw material composition.

[0084] 2. Heating process

[0085] The heating step in the present disclosure is a step of obtaining the sulfide solid electrolyte by heating the ion conductive material in an inert gas flow.

[0086] As the inert gas, for example, rare gases such as argon and helium can be cited. It should be noted that the inert gas may contain other gases within the range of obtaining the desired sulfide solid electrolyte. In addition, the flow rate of the inert gas is not particularly limited and can be appropriately set in a manner to obtain the desired sulfide solid electrolyte.

[0087] The heating conditions in the heating step are also appropriately set so as to obtain the desired sulfide solid electrolyte. The heating temperature is, for example, 300° C. or higher, 400° C. or higher, or 500° C. or higher. On the other hand, the heating temperature is, for example, 1000° C. or lower, or 700° C. or lower. In addition, the heating time is appropriately set so as to obtain the desired sulfide solid electrolyte.

[0088] 3. Sulfide solid electrolyte

[0089] The S2 / S1 ratio of the sulfide solid electrolyte obtained by the above-mentioned amorphization step and heating step is greater than or equal to a predetermined value. The composition of the sulfide solid electrolyte is not particularly limited. The preferred embodiment of the sulfide solid electrolyte is the same as that described in the above-mentioned "A. Sulfide solid electrolyte".

[0090] The present disclosure is not limited to the above-mentioned embodiments. The above-mentioned embodiments are illustrative only, and any technical solution having substantially the same structure and having the same function and effect as the technical concept described in the patent claims of the present disclosure is included in the technical scope of the present disclosure.

[0091] Example

[0092] In the following examples and comparative examples, in order to prevent oxidation and deterioration of the materials, all operations were performed without allowing the materials to come into contact with the atmosphere.

[0093] [Example 1]

[0094] As starting materials, lithium sulfide (Li2S, manufactured by Nippon Chemical Industry Co., Ltd.), phosphorus pentasulfide (P2S5, manufactured by Aldrich Co., Ltd.) and tin sulfide (SnS2, manufactured by Kojun Chemical Co., Ltd.) were used. These powders were mixed in a glove box under an argon atmosphere with Li 4-x Sn 1-x P x The mixture was weighed so that x=0.70 in S4 and mixed using an agate mortar. Thus, a raw material composition was obtained.

[0095] Next, in a glove box under an argon atmosphere, the obtained raw material composition and crushing balls (zirconia balls) were placed in a container (zirconia can), and the container was sealed. At this time, the volume of the crushing balls added was adjusted to about 1 / 6 of the volume of the container, and the weight of the added raw material composition was adjusted to about 1 / 50 of the weight of the crushing balls. The container was installed in a planetary ball mill (P7 made by Fritsch), and mechanical grinding was performed for 40 hours at a platen speed of 370 rpm. Thus, an ion conductive material was obtained.

[0096] Next, the obtained ion conductive material was placed on a graphite dish and heated in an Ar gas flow. The heating conditions were as follows. That is, the temperature was raised from room temperature to 570°C at a heating rate of 1.1°C / min, maintained at 570°C for 20 hours, and then slowly cooled to room temperature. Thus, a Li 4-x Sn 1-x P x The sulfide solid electrolyte having a composition represented by x=0.70 in S4.

[0097] [Examples 2 to 6]

[0098] A sulfide solid electrolyte was obtained in the same manner as in Example 1 except that the composition of the raw material composition and the heating temperature were changed to those shown in Table 1.

[0099] [Comparative Example 1]

[0100] The composition of the raw material composition is changed to Li 4-x Sn 1-x P x The ion conductive material was obtained in the same manner as in Example 1 except that x=0.64 in S4. The obtained ion conductive material was placed in a carbon-coated quartz tube and vacuum-sealed. The pressure of the vacuum-sealed quartz tube was about 30 Pa. Next, the quartz tube was placed in a sintering furnace, and the temperature was raised from room temperature to 500°C over 6 hours, maintained at 500°C for 8 hours, and then slowly cooled to room temperature. Thus, a Li 4-x Sn 1-x P x The sulfide solid electrolyte having a composition represented by x=0.64 in S4.

[0101] [Comparative Examples 2 to 4]

[0102] A sulfide solid electrolyte was obtained in the same manner as in Comparative Example 1 except that the composition of the raw material composition was changed to that shown in Table 1.

[0103] [Comparative Example 5]

[0104] A sulfide solid electrolyte was obtained in the same manner as in Example 1 except that the composition of the raw material composition and the heating temperature were changed to those shown in Table 1.

[0105] [Table 1]

[0106]

[0107] (X-ray diffraction measurement)

[0108] X-ray diffraction (XRD) measurements were performed on the sulfide solid electrolytes obtained in Examples 1 to 6 and Comparative Examples 1 to 5. The XRD measurements were performed on powder samples in an inert atmosphere using CuKα radiation. The results are shown in Figure 5 .like Figure 5 As shown, it was confirmed that the sulfide solid electrolytes obtained in Examples 1 to 6 and Comparative Examples 1 to 5 all had a LSnPS crystal phase (LGPS type crystal phase containing Li element, Sn element, P element, and S element).

[0109] In addition, in Comparative Examples 1 and 2, the peak of the Li4SnS4 crystal phase was confirmed in addition to the peak of the LSnPS crystal phase. However, in Examples 1 to 6 and Comparative Examples 3 to 5, the peak of the Li4SnS4 crystal phase was not confirmed, suggesting that the materials have the LSnPS crystal phase as a single phase.

[0110] ( 31 P-NMR measurement)

[0111] The sulfide solid electrolytes obtained in Examples 1 to 6 and Comparative Examples 1 to 5 were subjected to 31 P-NMR determination. 31 P-NMR measurement was performed under the following conditions.

[0112] Device: AVANCE400 manufactured by Bruker

[0113] Determination method: Single pulse method

[0114] Determined core frequency: 161.9810825MHz( 31 P core)

[0115] Spectrum width: 100.0kHz

[0116] Pulse width: 1.5μsec (45° pulse)

[0117] Pulse repetition time ACQTM: 0.0410150 seconds, pd = 3000 seconds

[0118] Number of observation points: 8192

[0119] Reference material: Diammonium hydrogen phosphate (external reference: 1.33ppm)

[0120] Temperature Room temperature: about 25℃

[0121] Sample speed: 9.5, 15kHz

[0122] The results are shown in Figure 6 .like Figure 6 As shown, it was confirmed that the sulfide solid electrolytes obtained in Examples 1 to 6 and Comparative Examples 1 to 5 all had LSnPS crystal phases. Specifically, in these sulfide solid electrolytes, the first peak was observed at around 77 ppm as a peak of the LSnPS crystal phase, which is PS4 (LSnPS-2b, Figure 2 In addition, in these sulfide solid electrolytes, a second peak was observed at around 93 ppm as a peak of the LSnPS crystal phase, which is PS4 (LSnPS-4d, Figure 2 The peak of tetrahedron T1).

[0123] In Comparative Examples 1 and 2, peaks of PS4 in phases other than the two LSnPS crystal phases were confirmed. These peaks correspond to the above Figure 1 (b) The third and fourth peaks. These two peaks are estimated to be peaks of PS4 in Li3PS4. In Examples 1 to 6 and Comparative Examples 3 to 5, the third and fourth peaks were also slightly confirmed.

[0124] As described above, the XRD measurement suggests that the sulfide solid electrolytes obtained in Examples 1 to 6 and Comparative Examples 3 to 5 are materials having a LSnPS crystal phase as a single phase. 31 When a precise P-NMR measurement was performed, it was confirmed that the sulfide solid electrolytes obtained in Examples 1 to 6 and Comparative Examples 3 to 5 contained a small amount of impurity components in addition to the LSnPS crystal phase.

[0125] In addition, if Figure 6 As shown, the peak of PS2O2 is slightly observed in the sulfide solid electrolytes obtained in Examples 1 to 6 and Comparative Examples 1 to 5. This peak corresponds to the above Figure 1(b) The fifth peak. PS2O2 is an oxygen-containing component that is inevitably contained. The peaks of the NMR graphs obtained in Examples 1 to 6 and Comparative Examples 3 to 5 were separated, and the area of ​​each peak was determined. The results are shown in Table 2.

[0126] [Table 2]

[0127]

[0128] In addition, in each embodiment and each comparative example, the total area of ​​the first to fifth peaks is calculated and set as S1 (S1=A+B+C+D+E). In addition, the total area of ​​the first peak and the second peak is calculated and set as S2 (S2=A+D). In addition, the total area of ​​the third peak and the fourth peak is calculated and set as S3 (S3=B+C). In addition, the area of ​​the fifth peak is set as S4 (S4=E). From these results, S2 / S1, S3 / S1, S4 / S1 and S4 / S2 are calculated. The results are shown in Table 3.

[0129] (Ionic conductivity measurement)

[0130] The ion conductivity of the sulfide solid electrolytes obtained in Examples 1 to 6 and Comparative Examples 1 to 5 was measured. First, 200 mg of the sulfide solid electrolyte was weighed and placed in a macole cylinder and heated at 4 tons / cm 2 The two ends of the obtained pressed sheet were clamped with SUS pins, and the pressed sheet was tightened with bolts to apply restraining pressure. The obtained sample was kept at 25°C, and the ion conductivity was calculated by AC impedance method. Solartron1260 was used in the measurement, the applied voltage was set to 5mV, and the measurement frequency range was set to 0.01~1MHz. The results are shown in Table 3.

[0131] [Table 3]

[0132]

[0133] As shown in Table 3, Examples 1 to 6 have a larger S2 / S1 and a higher ion conductivity than Comparative Examples 1 to 5. This is presumably because the sulfide solid electrolytes obtained in Examples 1 to 6 contain a large amount of LSnPS crystal phase. Figure 7 This is a graph showing the relationship between the ratio of the LSnPS crystal phase and the ion conductivity in the sulfide solid electrolytes obtained in Examples 1 to 6 and Comparative Examples 1 to 5. Figure 8 Yes Figure 7 A magnified image of a portion of the Figure 7 and Figure 8As shown in Table 3, by making S2 / S1 above 92.0%, the ion conductivity is significantly improved. The reason why S2 / S1 becomes larger and the reason why S3 / S1 becomes smaller in Examples 1 to 6 is speculated as follows: by heating in an inert gas flow, Li3PS4 as an impurity component is removed. In addition, it is speculated that by removing Li3PS4, the proportion of LSnPS crystal phase becomes relatively more, and the ion conductivity is improved. In addition, as shown in Table 3, S4 / S1 and S4 / S2 become smaller in Examples 1 to 6 than in Comparative Examples 1 to 5. The reason is speculated to be that by heating in an inert gas flow, Li3PS2O2 as an impurity component is removed. It is speculated that by removing Li3P2O2, the proportion of LSnPS crystal phase becomes relatively more, and the ion conductivity is improved.

Claims

1. A sulfide solid electrolyte having an LGPS type crystal phase containing Li, Sn, P and S elements, wherein: The sulfide solid electrolyte has Li 4-x Sn 1-x P x S4 represents the composition, where 0.67<x<0.76, The sulfide solid electrolyte 31 In the P-NMR measurement, there is a first peak having a vertex at a position of 77 ppm±1 ppm and a second peak having a vertex at a position of 93 ppm±1 ppm. In the 31 When the total area of ​​all peaks obtained by P-NMR measurement is defined as S1 and the total area of ​​the first peak and the second peak is defined as S2, the ratio S2 / S1 of S2 to S1 is 92.0% or more.

2. The sulfide solid electrolyte according to claim 1, wherein The sulfide solid electrolyte 31 In the P-NMR measurement, at least one of a third peak having a vertex at a position of 87 ppm±1 ppm and a fourth peak having a vertex at a position of 89 ppm±1 ppm is present, In the 31 When the total area of ​​all peaks obtained by P-NMR measurement is defined as S1 and the total area of ​​the third peak and the fourth peak is defined as S3, the ratio S3 / S1 of S3 to S1 is 6.0% or less.

3. The sulfide solid electrolyte according to claim 1 or 2, wherein The sulfide solid electrolyte 31 In the P-NMR measurement, there is a fifth peak having a peak at a position of 68 ppm±1 ppm, In the 31 When the area of ​​all peaks obtained by P-NMR measurement is defined as S1 and the area of ​​the fifth peak is defined as S4, the ratio S4 / S1 of S4 to S1 is 0.5% or less.

4. The sulfide solid electrolyte according to any one of claims 1 to 3, wherein The S2 / S1 is 95.0% or more.

5. The sulfide solid electrolyte according to any one of claims 1 to 4, wherein The x satisfies 0.67<x≤0.

74.

6. The sulfide solid electrolyte according to any one of claims 1 to 5, wherein The x satisfies 0.67<x≤0.

72.

7. The sulfide solid electrolyte according to any one of claims 1 to 6, wherein The sulfide solid electrolyte has an ion conductivity of 5.25 mS / cm or more at 25° C.

8. A battery comprising a positive electrode layer containing a positive electrode active material, a negative electrode layer containing a negative electrode active material, and an 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 electrolyte layer contains the sulfide solid electrolyte according to any one of claims 1 to 7.

9. A method for producing a sulfide solid electrolyte, which is a method for producing a sulfide solid electrolyte having an LGPS type crystal phase containing Li, Sn, P and S elements, comprising: Amorphization process, wherein The ion conductive material is obtained by amorphizing the raw material composition; and a heating step, wherein the sulfide solid electrolyte is obtained by heating the ion conductive material in an inert gas flow, The sulfide solid electrolyte 31 In the P-NMR measurement, as peaks of the LGPS type crystal phase, there are a first peak having a vertex at a position of 77 ppm±1 ppm and a second peak having a vertex at a position of 93 ppm±1 ppm. In the 31 When the total area of ​​all peaks obtained by P-NMR measurement is defined as S1 and the total area of ​​the first peak and the second peak is defined as S2, the ratio S2 / S1 of S2 to S1 is 92.0% or more.

Images