Sulfide solid electrolyte, method for producing same, and lithium ion conductive crystal

Abstract

The present invention relates to a sulfide solid electrolyte comprising a crystal phase and a glass phase, the glass phase comprising a phase comprising a sulfide-based glass containing Li, P, S, and Ha as constituent elements, the Ha being at least one type selected from F, Cl, Br, and I, the crystal phase comprising a high ion-conducting crystal phase derived from the sulfide-based glass, and the glass phase comprising a phase comprising a sulfide-based glass containing Li, P, S, and Ha as constituent elements. The high ion conduction crystal phase has diffraction peaks at least at 2 [theta] = 20.2 + / -0.5 DEG, 23.8 + / -0.5 DEG, and 29.7 + / -0.5 DEG in an XRD pattern obtained by powder X-ray diffraction measurement, and the half width of the diffraction peak at 2 [theta] = 20.2 + / -0.5 DEG is 0.01-0.4 DEG.

Description

Technical Field

[0001] This invention relates to sulfide solid electrolytes and methods for manufacturing the same. Furthermore, this invention also relates to novel lithium-ion conductive crystals. Background Technology

[0002] Lithium-ion rechargeable batteries are widely used in portable electronic devices such as mobile phones and laptops, as well as automobiles.

[0003] Previously, liquid electrolytes were used in lithium-ion rechargeable batteries, but this raised concerns about leakage and fire. For safety reasons, larger casings were necessary. Furthermore, improvements were desired to address issues such as short battery life and narrow operating temperature range.

[0004] In response, all-solid-state lithium secondary batteries, which use solid electrolytes as the electrolyte for lithium-ion secondary batteries, have attracted much attention due to the anticipated improvements in safety, high-speed charging and discharging, and miniaturization of the casing.

[0005] Solid electrolytes are broadly classified into sulfide solid electrolytes and oxide solid electrolytes. Sulfide ions, which constitute sulfide solid electrolytes, exhibit higher polarizability and thus higher ionic conductivity compared to oxide ions, which constitute oxide solid electrolytes. Li₂ is a known sulfide solid electrolyte. 10 GeP2S 12 Crystals of the LGPS type, such as Li6PS5Cl, and Li7P3S 11 Crystallized glass, LPS crystallized glass, etc.

[0006] As a solid electrolyte that is not easily hydrolyzed and has high ionic conductivity, Patent Document 1 discloses a crystallized solid electrolyte containing lithium, phosphorus, sulfur and Br as constituent components and having a specific crystal structure.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2013-201110 Summary of the Invention

[0010] The crystallized solid electrolyte described in Patent Document 1 is a sulfide-based glass obtained by mechanical grinding that is crystallized by heat treatment.

[0011] However, the crystallized solid electrolytes described above have low crystallinity, and it is desirable to achieve higher lithium-ion conductivity.

[0012] Therefore, the object of this invention is to provide a sulfide solid electrolyte with excellent lithium-ion conductivity and a method for manufacturing the same. Furthermore, another object of this invention is to provide a novel crystal with excellent lithium-ion conductivity.

[0013] Through repeated and in-depth research, the inventors conceived of a method for obtaining a sulfide-based glass phase by heating and cooling raw materials, performing the heating and cooling under ambient pressure at a very rapid rate. They discovered that if a portion of the resulting glass phase is crystallized, a sulfide solid electrolyte with high crystallinity and high lithium-ion conductivity can be obtained.

[0014] That is, the present invention relates to the following [1] to [8].

[0015] [1] A sulfide solid electrolyte comprising a crystalline phase and a glassy phase,

[0016] The aforementioned glass phase comprises a phase consisting of sulfide-based glasses containing Li, P, S, and Ha as constituent elements.

[0017] The above-mentioned Ha is at least one selected from F, Cl, Br and I.

[0018] The aforementioned crystalline phase includes a highly ion-conducting crystalline phase derived from the aforementioned sulfide-based glass.

[0019] The aforementioned high ion conductivity crystalline phase exhibits diffraction peaks at at least 2θ = 20.2 ± 0.5°, 23.8 ± 0.5°, and 29.7 ± 0.5° in the XRD pattern obtained by powder X-ray diffraction.

[0020] The half-width at half-maximum (FWHM) of the diffraction peak at 2θ = 20.2 ± 0.5° is 0.01–0.4°.

[0021] [2] According to the sulfide solid electrolyte described in [1] above, in the XRD pattern of the high ion conductivity crystalline phase, the peak intensity of the diffraction peak at 2θ = 20.2 ± 0.5° is set as I. A The peak intensity of the diffraction peak with 2θ = 29.7 ± 0.5° is set as I. B At that time, I A / I B The indicated peak intensity ratio exceeds 1.0.

[0022] [3] According to the sulfide solid electrolyte described in [1] or [2] above, wherein the content of the high ion conductivity crystal phase in the sulfide solid electrolyte is 50% by mass or more.

[0023] [4] The sulfide solid electrolyte according to any one of [1] to [3] above, wherein the composition of the phase composed of the sulfide glass and the high ion conductivity crystal phase satisfies Li: 30 to 50 at%, P: 5 to 15 at%, S: 30 to 60 at%, and Ha: 1 to 12 at%.

[0024] [5] The sulfide solid electrolyte according to any one of [1] to [4] above, wherein the above-mentioned high ion conductivity crystal phase further has a diffraction peak in the above-mentioned XRD pattern at at least one of the following selected from 2θ = 12.4 ± 0.5°, 14.4 ± 0.5° and 31.4 ± 0.5°.

[0025] [6] A lithium-ion conductive crystal comprising Li, P, S and Ha as constituent elements.

[0026] The above-mentioned Ha is at least one selected from F, Cl, Br and I.

[0027] In the XRD patterns obtained by powder X-ray diffraction, diffraction peaks were observed at least at 2θ = 12.4 ± 0.5°, 14.4 ± 0.5°, 20.2 ± 0.5°, 23.8 ± 0.5°, 29.7 ± 0.5°, and 31.4 ± 0.5°.

[0028] Let the peak intensity of the diffraction peak at 2θ = 20.2 ± 0.5° be I. A The peak intensity of the diffraction peak with 2θ = 29.7 ± 0.5° is set as I. B At that time, I A / I B The indicated peak intensity ratio exceeds 1.0.

[0029] [7] A method for manufacturing a sulfide solid electrolyte, comprising the following steps in sequence:

[0030] The raw materials are mixed to obtain a raw material mixture containing Li, P and S.

[0031] Heating the above raw material mixture yields a melt.

[0032] The above-mentioned melt is cooled and solidified to obtain the above-mentioned glass phase, and

[0033] Heating the glassy phase yields a portion of a highly ion-conducting crystalline phase by crystallization.

[0034] The heating and cooling solidification used to obtain the above-mentioned melt are carried out under normal pressure conditions.

[0035] The cooling rate during the above-mentioned cooling and curing process is 100°C / second or higher.

[0036] The heating used to obtain the above-mentioned high ion conductivity crystalline phase is performed at a temperature that is at or above the crystallization temperature of the above-mentioned glass phase (the above-mentioned crystallization temperature - 15°C) for at least 1 minute.

[0037] The aforementioned sulfide solid electrolyte comprises the aforementioned glass phase and the aforementioned highly ion-conducting crystalline phase.

[0038] [8] According to the method for manufacturing the sulfide solid electrolyte described in [7] above, wherein the raw material mixture further comprises Ha,

[0039] The above-mentioned Ha is at least one selected from F, Cl, Br and I.

[0040] According to the present invention, a sulfide solid electrolyte with high crystallinity and excellent lithium-ion conductivity can be obtained. Therefore, when the above-mentioned sulfide solid electrolyte is used in an all-solid-state lithium secondary battery, good battery characteristics can be achieved. In addition, the lithium-ion conductive crystal obtained by the present invention has high conductivity and is suitable for sulfide solid electrolytes. Attached Figure Description

[0041] Figure 1 This is a flowchart illustrating the method for manufacturing the sulfide solid electrolyte of this embodiment.

[0042] Figure 2 The image shows the XRD pattern of the sulfide solid electrolyte obtained in Example 2.

[0043] Figure 3 The image shows the XRD pattern of the sulfide solid electrolyte obtained in Example 5. Detailed Implementation

[0044] The present invention will now be described in detail, but the invention is not limited to the embodiments described below, and can be implemented in any modified form without departing from the spirit of the invention. Furthermore, the symbol “~” indicating a numerical range is used to mean that the values ​​before and after it are both lower and upper limits.

[0045] Sulfide Solid Electrolytes

[0046] The sulfide solid electrolyte of this embodiment comprises a crystalline phase and a glassy phase. The glassy phase comprises a phase composed of a sulfide-based glass (hereinafter, sometimes simply referred to as the "sulfide-based glassy phase"), which contains Li, P, S, and Ha as constituent elements. The crystalline phase comprises a highly ion-conducting crystalline phase derived from the sulfide-based glass. Here, Ha is at least one selected from F, Cl, Br, and I.

[0047] The high ion conductivity crystalline phase from sulfide-based glasses refers to the crystalline phase formed by crystallizing the aforementioned sulfide-based glasses through heat treatment. It can be considered to have approximately the same constituent elements and compositional ratios. Here, "approximately the same constituent elements and compositional ratios" means that the differences in composition between each component and the overall composition, as determined by structural analysis based on the XRD patterns of the high ion conductivity crystalline phase, are all within ±20%.

[0048] The aforementioned high ion conductivity crystalline phase exhibits diffraction peaks at at least 2θ = 20.2 ± 0.5°, 23.8 ± 0.5°, and 29.7 ± 0.5° in its XRD pattern obtained by powder X-ray diffraction. Among these diffraction peaks, the half-width at 2θ = 20.2 ± 0.5° is 0.01–0.4°.

[0049] <Phase composed of sulfide-based glasses and highly ion-conducting crystalline phases>

[0050] The sulfide-based glassy phase and the highly ion-conducting crystalline phase in this embodiment contain Li, P, S, and Ha as constituent elements. Here, Ha is at least one selected from F, Cl, Br, and I. From the viewpoint of obtaining good antioxidant and water-resistant properties, it is more preferable to contain at least one selected from Cl, Br, and I, further preferably to contain at least one selected from Cl and Br, and even more preferably to contain Br. In addition, it is even more preferable to contain both Cl and Br.

[0051] In this embodiment, the high ion conductivity crystalline phase exhibits diffraction peaks at at least 2θ = 20.2 ± 0.5°, 23.8 ± 0.5°, and 29.7 ± 0.5° in the XRD pattern obtained by powder X-ray diffraction (XRD). Among these diffraction peaks, the peak at 2θ = 20.2 ± 0.5° has a full width at half maximum (FWHM) of 0.01 to 0.4°.

[0052] The above XRD measurements were performed using CuKα rays (λ = 1.5418 Å) as the radiation source. The details of the measurement conditions are described in the following examples.

[0053] Furthermore, the half-width at half-maximum (FWHM) of a peak in this specification refers to the width of the diffraction line at half the height of the diffraction line intensity. That is, the FWHM refers to the width at which half the peak intensity intersects with the peak when an XRD pattern is plotted.

[0054] Here, the crystallized solid electrolyte described in Patent Document 1 also exhibits diffraction peaks at 2θ = 20.2 ± 0.5°, 23.8 ± 0.5°, and 29.7 ± 0.5° (refer to Patent Document 1, [Figure 6] Example 12, etc.). However, among the aforementioned diffraction peaks, the half-width at 2θ = 20.2 ± 0.5° is approximately 0.5 to 0.6°, which does not achieve the higher crystallinity. Consequently, their lithium-ion conductivity is approximately 2 mS / cm.

[0055] In contrast, the high ion conductivity crystalline phase in this embodiment has a half-width of 0.01 to 0.4° at 2θ = 20.2 ± 0.5°, exhibiting high crystallinity, while its lithium ion conductivity is as high as about 3 mS / cm.

[0056] The reason has not yet been determined, but the following can be considered.

[0057] If sulfide-based glasses are obtained using conventional mechanical grinding methods, as described in Patent Document 1 for crystallizing solid electrolytes, the physical energy of the ball mill or similar equipment causes the crystal structure of the raw materials to become disordered, i.e., lacking a regular atomic arrangement, resulting in amorphous glass. Therefore, even if such sulfide-based glasses are subjected to heat treatment to crystallize, high crystallinity cannot be achieved, and the improvement in lithium-ion conductivity will reach its limit.

[0058] In contrast, the sulfide solid electrolyte of this embodiment employs a melt-quenching method to obtain the glassy phase. Furthermore, heating and cooling of the molten raw materials are performed under atmospheric pressure at a very rapid cooling rate. It is speculated that while the glassy phase in this embodiment may not reach the level observed in XRD patterns, it may possess a certain degree of order, i.e., a periodic structure. Moreover, it is believed that if such a glassy phase is heat-treated to crystallize, its crystallinity will increase, potentially leading to higher lithium-ion conductivity.

[0059] Regarding the high ion conductivity crystalline phase in this embodiment, in the above diffraction peaks, the half-width of the peak at 2θ = 20.2 ± 0.5° is 0.01 to 0.4°. If the half-width is below 0.4°, it can be judged as having high crystallinity.

[0060] The aforementioned half-width at half-maximum (HWHM) is preferably 0.05° to 0.35°, more preferably 0.1° to 0.3°. From the viewpoint of increasing lithium-ion conductivity associated with high crystallinity, the HWHM is preferably 0.35° or less, more preferably 0.3° or less. Furthermore, the lower limit of the HWHM is not particularly limited; a smaller value is preferred. However, from the viewpoint of the detection accuracy of the device, it can be 0.05° or more, or 0.1° or more.

[0061] In this embodiment, the high ion conductivity crystalline phase, in the XRD pattern obtained by powder X-ray diffraction, preferably has a diffraction peak at at least one of the following 2θ = 12.4 ± 0.5°, 14.4 ± 0.5°, and 31.4 ± 0.5°, in addition to 2θ = 20.2 ± 0.5°, 23.8 ± 0.5°, and 29.7 ± 0.5°; more preferably, it has a diffraction peak at at least two 2θ = 12.4 ± 0.5°, and more preferably, it has a diffraction peak at all three 2θ = 12.4 ± 0.5°.

[0062] In the XRD pattern of the high ion conductivity crystalline phase in this embodiment, the peak intensity of the diffraction peak at 2θ = 20.2 ± 0.5° is set as I. A The peak intensity of the diffraction peak with 2θ = 29.7 ± 0.5° is set as I. B At that time, I A / I B The indicated peak intensity ratio is preferably greater than 1.0, more preferably greater than 1.0 and less than 2.0, further preferably 1.05 to 1.8, even more preferably 1.05 to 1.5, particularly preferably 1.1 to 1.45, and most preferably 1.1 to 1.4.

[0063] Regarding the aforementioned peak intensity ratio, in the case of crystallizing the sulfide-based glass obtained by mechanical grinding, I A / I B The peak intensity ratio is represented as less than 1.0, i.e., the peak intensity I of the diffraction peak at 2θ = 20.2 ± 0.5°. A In comparison, the peak intensity I of the diffraction peak at 2θ = 29.7 ± 0.5° B Larger or the same.

[0064] In contrast, according to the research of the inventors, when a sulfide-based glass obtained by a melt-quenching method under specific conditions is crystallized, I A / I B The peak intensity I represents the peak intensity of a diffraction peak with a peak intensity ratio exceeding 1.0, i.e., 2θ = 20.2 ± 0.5°. A The peak intensity I of the diffraction peak greater than 2θ = 29.7 ± 0.5° B This can be said to be a characteristic of the crystalline phase obtained for the first time due to the use of the above-mentioned melt-quenching method.

[0065] Based on the above, I A / I B The peak intensity ratio expressed is only required to be greater than 1.0, but from the viewpoint of lithium-ion conductivity, it is preferably 1.05 or more, more preferably 1.1 or more, and preferably 2.0 or less, more preferably 1.8 or less, even more preferably 1.5 or less, even more preferably 1.45 or less, and particularly preferably 1.4 or less.

[0066] It should be noted that the presence of diffraction peaks at 2θ = 20.2 ± 0.5°, 23.8 ± 0.5°, and 29.7 ± 0.5° in the XRD pattern indicates that the high ion conductivity crystal phase employs a Thio-LISICON or LGPS type crystal structure. These phases exhibit high lithium-ion conductivity.

[0067] In this embodiment, the compositions of the sulfide-based glass phase and the highly ion-conducting crystalline phase preferably satisfy Li: 30–50 at%, P: 5–15 at%, S: 30–60 at%, and Ha: 1–12 at%. It should be noted that in this specification, at% refers to atomic%. Furthermore, as mentioned above, the sulfide-based glass and the highly ion-conducting crystalline phase derived from it can be considered to have approximately the same constituent elements and compositional ratios, but this does not mean they are strictly identical. Preferably, the compositions of the sulfide-based glass phase and the highly ion-conducting crystalline phase each satisfy the above-mentioned ranges.

[0068] In the sulfide-based glass phase and the highly ion-conducting crystalline phase of this embodiment, Li is the element responsible for ion conduction as a solid electrolyte.

[0069] In the composition of the sulfide-based glassy phase and the highly ion-conducting crystalline phase, the Li content is preferably 30–50 at%, more preferably 35–45 at%, and even more preferably 37–43 at%. From the viewpoint of improving lithium-ion conductivity, the aforementioned Li content is preferably 30 at% or more, more preferably 35 at% or more, and even more preferably 37 at% or more. Furthermore, from the viewpoint of expanding the glass transition range, the Li content is preferably 50 at% or less, more preferably 45 at% or less, and even more preferably 43 at% or less.

[0070] In the sulfide-based glass phase and the highly ion-conducting crystalline phase of this embodiment, P is the element that forms the glass network, and the P-S bond in the sulfide exhibits high resistance to both oxidation and reduction. Therefore, as a solid electrolyte, it has a wide potential window and excellent electrochemical stability.

[0071] In the composition of the sulfide-based glassy phase and the high ion conductivity crystalline phase, the phosphorus (P) content is preferably 5–15 at%, more preferably 6–13 at%, and even more preferably 7–12 at%. From the viewpoint of broadening the glass transition range, the aforementioned P content is preferably 5 at% or more, more preferably 6 at% or more, and even more preferably 7 at% or more. Furthermore, from the viewpoint of improving lithium-ion conductivity, the P content is preferably 15 at% or less, more preferably 13 at% or less, and even more preferably 12 at% or less.

[0072] In the sulfide-based glass phase and the highly ion-conducting crystalline phase of this embodiment, S is an element that forms P-S bonds together with P and is an essential element for the formation of the glass phase.

[0073] In the composition of the sulfide-based glassy phase and the highly ion-conducting crystalline phase, the sulfur (S) content is preferably 30–60 at%, more preferably 33–50 at%, and even more preferably 35–47 at%. From the viewpoint of broadening the glass transition range, the S content is preferably 30 at% or more, more preferably 33 at% or more, and even more preferably 35 at% or more. Furthermore, from the viewpoint of improving lithium-ion conductivity, the S content is preferably 60 at% or less, more preferably 50 at% or less, and even more preferably 47 at% or less.

[0074] In the sulfide-based glass phase and the high ion conductivity crystal phase of this embodiment, Ha is an element that contributes to high lithium-ion conductivity.

[0075] In the composition of the sulfide-based glassy phase and the highly ion-conducting crystalline phase, the Ha content is preferably 1 to 12 at%, more preferably 3 to 10 at%, and even more preferably 3.5 to 8 at%. Here, from the viewpoint of obtaining high lithium-ion conductivity, the Ha content is preferably 1 at% or more, more preferably 3 at% or more, and even more preferably 3.5 at% or more. In addition, in order to prevent the precipitation of lithium halide crystals, the Ha content is preferably 12 at% or less, more preferably 10 at% or less, and even more preferably 8 at% or less. It should be noted that the Ha content here refers to the total content of F, Cl, Br, and I.

[0076] Ha is selected from at least one of F, Cl, Br and I. As mentioned above, from the viewpoint of obtaining good antioxidant properties and water resistance, it is more preferable to include at least one of Cl and Br, and even more preferable to include Br. In addition, it is even more preferable to include both Cl and Br.

[0077] For example, in the above-mentioned Ha content, the total content of Cl and Br is preferably 50 at% or more, more preferably 70 at% or more, and may also be 100 at% (i.e., composed only of Cl and Br). Furthermore, the atomic ratio of Cl:Br is preferably 100:0 to 0:100, more preferably 80:20 to 0:100, and even more preferably 60:40 to 0:100.

[0078] In this embodiment, the sulfide-based glass phase and the highly ion-conducting crystalline phase may also contain other elements besides Li, P, S, and Ha as constituent elements. Examples of other elements that may be included include Si, B, Ge, Al, O, Na, K, Mg, Ca, Sr, Ba, Y, Zr, Cr, Zn, Ga, Sn, and Sb.

[0079] Of these, the other elements mentioned above, when constituting oxides such as SiO2, B2O3, P2O5, and Al2O3, are preferably excluded because these oxides would act as crystal nuclei. The total content of oxides, expressed as mol% based on oxides, is preferably 1 mol% or less, more preferably 0.1 mol% or less, even more preferably 0.05 mol% or less, and may also be excluded, i.e., 0 mol%.

[0080] In this embodiment, the sulfide-based glass phase and the highly ion-conducting crystalline phase may also include, for example, Si, B, Ge, Al, Sn, and Sb among the other elements mentioned above. These Si, B, Ge, Al, Sn, and Sb are elements that may enter P positions during the crystallization of the sulfide-based glass phase.

[0081] In this embodiment, when the sulfide-based glass phase and the highly ion-conducting crystalline phase contain Si as a constituent element, Si has the effect of increasing the viscosity of the molten liquid and promoting vitrification. The Si content is preferably 0 to 15 at%, more preferably 0.1 to 10 at%, and even more preferably 1 to 5 at%. Here, from the viewpoint of appropriately obtaining the effects brought by Si, the Si content is preferably 0.1 at% or more, and more preferably 1 at% or more. Furthermore, from the viewpoint of electrochemical stability, the Si content is preferably 15 at% or less, more preferably 10 at% or less, and even more preferably 5 at% or less.

[0082] However, when Si has Si-O bonds or is contained in the form of SiO2 oxides, as described above, the Si content is appropriately adjusted so that the total content of oxides is less than 1 mol%, or the total content of oxides that form the network of glass is 3 to 20 mol%.

[0083] In this embodiment, when the sulfide-based glass phase and the high ion conductivity crystalline phase contain boron (B) as a constituent element, B has the effect of increasing the viscosity of the molten liquid and promoting vitrification. The B content is preferably 0 to 15 at%, more preferably 0.1 to 10 at%, and even more preferably 1 to 5 at%. From the viewpoint of appropriately obtaining the effects brought by B, the B content is preferably 0.1 at% or more, and more preferably 1 at% or more. Furthermore, from the viewpoint of lithium-ion conductivity, the B content is preferably 15 at% or less, more preferably 10 at% or less, and even more preferably 5 at% or less.

[0084] However, when B has B-O bonds or is contained in the form of oxides of B2O3, as described above, the content of B is appropriately adjusted so that the total content of oxides is less than 1 mol%, or the total content of oxides that form the network of glass is 3 to 20 mol%.

[0085] In this embodiment, when the sulfide-based glass phase and the high ion conductivity crystal phase contain Ge as a constituent element, Ge has the effect of promoting increased lithium-ion conductivity. The Ge content is preferably 0 to 15 at%, more preferably 0.1 to 10 at%, and even more preferably 1 to 5 at%. Here, from the viewpoint of lithium-ion conductivity, the Ge content is preferably 0.1 at% or more, and more preferably 1 at% or more. Furthermore, from the viewpoint of ease of glass formation, the Ge content is preferably 15 at% or less, more preferably 10 at% or less, and even more preferably 5 at% or less.

[0086] However, when Ge has Ge-O bonds or is contained in the form of GeO2 oxides, the Ge content is appropriately adjusted as described above so that the total content of oxides is less than 1 mol%.

[0087] In this embodiment, when the sulfide-based glass phase and the high ion conductivity crystalline phase contain Al as a constituent element, Al has the effect of increasing the viscosity of the molten liquid and promoting vitrification. The Al content is preferably 0 to 15 at%, more preferably 0.1 to 10 at%, and even more preferably 1 to 5 at%. Here, from the viewpoint of appropriately obtaining the effect brought by Al, the Al content is preferably 0.1 at% or more, and more preferably 1 at% or more. Furthermore, from the viewpoint of lithium-ion conductivity, the Al content is preferably 15 at% or less, more preferably 10 at% or less, and even more preferably 5 at% or less.

[0088] In cases where Al has Al-O bonds or is contained in the form of Al2O3 oxides, the Al content is appropriately adjusted as described above so that the total content of oxides is 1 mol% or less, or the total content of oxides that form the network of glass is 3 to 20 mol%.

[0089] In this embodiment, when the sulfide-based glass phase and the high ion conductivity crystalline phase contain Sn as a constituent element, Sn has the effect of increasing the viscosity of the molten liquid and promoting vitrification. The Sn content is preferably 0 to 15 at%, more preferably 0.1 to 10 at%, and even more preferably 1 to 5 at%. Here, from the viewpoint of appropriately obtaining the effects brought by Sn, the Sn content is preferably 0.1 at% or more, and more preferably 1 at% or more. Furthermore, from the viewpoint of achieving high lithium-ion conductivity, the Sn content is preferably 15 at% or less, more preferably 10 at% or less, and even more preferably 5 at% or less.

[0090] However, when Sn has Sn-O bonds or is contained in the form of SnO2 oxides, as described above, Sn is appropriately adjusted so that the total content of oxides is less than 1 mol%.

[0091] When the sulfide-based glass phase and the high ion conductivity crystalline phase in this embodiment contain Sb as a constituent element, Sb has the effect of increasing the viscosity of the molten liquid and promoting vitrification. The Sb content is preferably 0 to 15 at%, more preferably 0.1 to 10 at%, and even more preferably 1 to 5 at%. Here, from the viewpoint of appropriately obtaining the effect brought by Sb, the Sb content is preferably 0.1 at% or more, and more preferably 1 at% or more. Furthermore, from the viewpoint of lithium-ion conductivity, the Sb content is preferably 15 at% or less, more preferably 10 at% or less, and even more preferably 5 at% or less.

[0092] However, when Sb has Sb-O bonds or is contained in the form of oxides of Sb2O3, as described above, the Sb content is appropriately adjusted so that the total content of oxides is less than 1 mol%, or the total content of oxides that form the network of glass is 3 to 20 mol%.

[0093] In the composition of the sulfide-based glass phase and the highly ion-conducting crystalline phase in this embodiment, the Li / P ratio is preferably 2.5 or more, more preferably 2.5 to 7.0, even more preferably 3.0 to 6.5, and even more preferably 3.2 to 6.2.

[0094] From the viewpoint of obtaining high lithium-ion conductivity, the above-mentioned composition ratio is preferably 2.5 or more, more preferably 3.0 or more, and even more preferably 3.2 or more. Furthermore, from the viewpoint of broadening the glass transition range, the above-mentioned composition ratio is preferably 7.0 or less, more preferably 6.5 or less, and even more preferably 6.2 or less.

[0095] It should be noted that in this specification, the composition ratio refers to the ratio (at%) of each element in the sulfide-based glass phase and the highly ion-conducting crystalline phase.

[0096] In the composition of the sulfide-based glass phase and the highly ion-conducting crystalline phase in this embodiment, the S / P ratio is preferably 3.0 to 5.0, more preferably 3.5 to 4.5, and even more preferably 3.8 to 4.2. From the viewpoint of lithium-ion conductivity, the above-mentioned composition ratio is preferably 3.0 or more, more preferably 3.5 or more, and even more preferably 3.8 or more. Furthermore, from the viewpoint of water resistance, the above-mentioned composition ratio is preferably 5.0 or less, more preferably 4.5 or less, and even more preferably 4.2 or less.

[0097] In the composition of the sulfide-based glassy phase and the highly ion-conducting crystalline phase, the composition ratio represented by [(F + Cl + Br) / Ha] is preferably 0.5 or more, more preferably 0.5 to 1.0, even more preferably 0.6 to 1.0, and particularly preferably 0.8 to 1.0. Here, from the viewpoint of antioxidant properties, the above composition ratio is preferably 0.5 or more, more preferably 0.6 or more, and even more preferably 0.8 or more. In addition, the upper limit of the above composition ratio is not particularly limited, and can be 1.0. The above composition ratio of 1.0 means that I is not present as Ha. When the sulfide-based glassy phase and the highly ion-conducting crystalline phase contain I as Ha, from the viewpoint of obtaining the effect brought by I, the above composition ratio can be 0.8 or less, or 0.6 or less.

[0098] In the composition of the sulfide-based glassy phase and the highly ion-conducting crystalline phase, the composition ratio represented by Ha / P is preferably 0.01 to 1.5, more preferably 0.1 to 1.2, and even more preferably 0.2 to 1.0. From the viewpoint of water resistance, the above composition ratio is preferably 0.01 or more, more preferably 0.1 or more, and even more preferably 0.2 or more. Furthermore, from the viewpoint of lithium halide crystal precipitation, the above composition ratio is preferably 1.5 or less, more preferably 1.2 or less, and even more preferably 1.0 or less. It should be noted that Ha here refers to the total of F, Cl, Br, and I.

[0099] The constituent elements and their contents of the sulfide-based glassy phase and the high ion conductivity crystalline phase were determined by comparing the results of measuring the constituent elements and their contents (composition ratios) of the sulfide solid electrolyte as a whole, and by calculating the element ratios that constitute the crystal structure based on XRD patterns.

[0100] It should be noted that the constituent elements and their contents of the above-mentioned sulfide solid electrolytes are determined differently depending on the element. For example, they can be determined by analyzing P and S using ICP emission spectroscopy, Li using atomic absorption spectrometry, and Ha using ion chromatography. Details of each analysis are described in the examples described later.

[0101] In this embodiment, the sulfide-based glassy phase is partially crystallized through heat treatment, thus becoming the high ion conductivity crystalline phase of this embodiment. This high ion conductivity crystalline phase can adopt a Thio-Lisicon type or LGPS type crystal structure. Thio-Lisicon type and LGPS type high ion conductivity crystalline phases have high lithium-ion conductivity and are useful as solid electrolytes.

[0102] In this embodiment, the total ratio of the sulfide-based glass phase and the highly ion-conducting crystalline phase in the sulfide solid electrolyte is preferably 50-100% by mass, more preferably 70-95% by mass, and even more preferably 80-90% by mass. From the viewpoint of lithium-ion conductivity, this total ratio is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more. Alternatively, the total ratio can be 100% by mass, meaning it consists only of the sulfide-based glass phase and the highly ion-conducting crystalline phase. On the other hand, when obtaining the sulfide-based glass phase, the crystalline phase may also be obtained simultaneously. Obtaining only the sulfide-based glass phase and the highly ion-conducting crystalline phase would be time-consuming and costly. Therefore, from the viewpoint of manufacturability of the sulfide solid electrolyte, the total ratio is more preferably 95% by mass or less, and even more preferably 90% by mass or less.

[0103] It should be noted that the respective proportions of the sulfide-based glassy phase and the highly ion-conducting crystalline phase can be determined by powdering the sulfide solid electrolyte into powder, performing powder X-ray diffraction (XRD) together with the crystalline powder used as an internal standard, and then performing Rietwald analysis. The proportion of the sulfide-based glassy phase can be obtained by subtracting the proportion of the crystalline phase from 100% by mass after determining the proportion of the crystalline phase using the above analysis.

[0104] The content of the high ion conductivity crystalline phase in the sulfide solid electrolyte of this embodiment is preferably 30% by mass or more, more preferably 50% by mass or more or 30 to 90% by mass, even more preferably 50 to 85% by mass, and even more preferably 60 to 80% by mass. Here, from the viewpoint of lithium-ion conductivity, the above-mentioned content is preferably 30% by mass or more, more preferably 50% by mass or more, and even more preferably 60% by mass or more. In addition, from the viewpoint of appropriately obtaining the effect brought about by the phase composed of sulfide-based glass, the above-mentioned content is preferably 90% by mass or less, more preferably 85% by mass or less, and even more preferably 80% by mass or less.

[0105] The content of the sulfide-based glass phase in the sulfide solid electrolyte of this embodiment is preferably 1 to 70% by mass, more preferably 5 to 50% by mass, and even more preferably 8 to 40% by mass. From the viewpoint of utilizing the glass phase to achieve a flexible interface that facilitates the formation of the active material and the solid electrolyte, the above-mentioned content is preferably 1% by mass or more, more preferably 5% by mass or more, and even more preferably 8% by mass or more. Furthermore, from the viewpoint of appropriately obtaining the effect of a highly ion-conducting crystalline phase, the above-mentioned content is preferably 70% by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less.

[0106] Other phases

[0107] The sulfide solid electrolyte of this embodiment may also include other phases besides the sulfide-based glass phase and the highly ion-conducting crystalline phase described above. Examples of such other phases include the crystalline phase obtained simultaneously during the manufacture of the sulfide-based glass phase.

[0108] The proportion of such other phases in the sulfide solid electrolyte is 40% by mass or less, preferably 1 to 40% by mass, more preferably 2 to 35% by mass, and even more preferably 5 to 30% by mass. Here, from the viewpoint of fully utilizing the characteristics brought by the sulfide-based glassy phase and the highly ion-conducting crystalline phase, the total proportion of other phases is 40% by mass or less, preferably 35% by mass or less, and even more preferably 30% by mass or less. In addition, although it is also possible to exclude other phases, from the viewpoint of the manufacturability of the sulfide solid electrolyte, the total proportion of other phases is preferably 1% by mass or more, more preferably 2% by mass or more, and even more preferably 5% by mass or more.

[0109] Properties of Sulfide Solid Electrolytes

[0110] When the sulfide solid electrolyte of this embodiment is formed into a pressed powder at 380 MPa, its lithium-ion conductivity at 25°C is preferably 2.5 mS / cm or higher. This is because the lithium-ion conductivity of the aforementioned sulfide-based glass phase and the high-ion-conductivity crystalline phase derived from the sulfide-based glass phase is high. However, since it is difficult to extract only the sulfide-based glass phase and the high-ion-conductivity crystalline phase from the sulfide solid electrolyte, the lithium-ion conductivity of the sulfide-based glass phase and the high-ion-conductivity crystalline phase is evaluated by the lithium-ion conductivity of the aforementioned sulfide solid electrolyte.

[0111] The lithium-ion conductivity of the sulfide solid electrolyte in this embodiment is preferably 2.5 mS / cm or higher, and the higher the better. However, its value also varies depending on the composition, the proportion of sulfide-based glass phase, and high-ion-conductivity crystalline phase.

[0112] For example, when Ha contains Br content of 90 at% or more, the lithium-ion conductivity is preferably 3.0 mS / cm or more. In addition, when Ha contains Cl content of 90 at% or more, the lithium-ion conductivity is preferably 2.5 mS / cm or more.

[0113] It should be noted that the lithium-ion conductivity in this specification can be determined by pressing the powder of the sulfide solid electrolyte into a powder at 380 MPa and then using it as a test sample for AC impedance measurement. Specifically, the AC impedance of the test sample is measured at a measurement frequency of 100 Hz to 1 MHz, a measurement voltage of 100 mV, and a measurement temperature of 25 °C. The value obtained from the resulting Nyquist plot is taken as the lithium-ion conductivity.

[0114] The average particle size (D50) of the sulfide solid electrolyte in this embodiment is preferably 0.1 to 300 μm, more preferably 0.3 to 50 μm, and even more preferably 0.5 to 5 μm. Here, from the viewpoint of reducing the load on the micronization process when using the sulfide solid electrolyte in a secondary battery, the above-mentioned average particle size is preferably 300 μm or less, more preferably 50 μm or less, and even more preferably 5 μm or less. Furthermore, from the viewpoint of powder handling, the above-mentioned average particle size is preferably 0.1 μm or more, more preferably 0.3 μm or more, and even more preferably 0.5 μm or more.

[0115] The aforementioned average particle size (D50) can be adjusted by coarsely grinding the obtained sulfide solid electrolyte. Coarse grinding can be performed using conventionally known methods, such as cutting mills, planetary ball mills, and jet mills; dry grinding is preferred. Then, further finer particle sizes are formed using wet or dry grinding methods such as bead mills or jet mills, resulting in a solid electrolyte that is used as a positive electrode, negative electrode, or separator layer in battery materials.

[0116] The sulfide solid electrolyte of this embodiment is suitable as an electrolyte for lithium-ion secondary batteries. When the sulfide solid electrolyte is used in a lithium-ion secondary battery, it is formed into a solid electrolyte layer together with other components such as binders, as needed. Conventionally known substances can be used as binders and other components.

[0117] In this embodiment, the content of sulfide solid electrolyte is preferably 80% by mass or more, and more preferably 90% by mass or more, relative to the overall solid electrolyte layer.

[0118] Furthermore, the sulfide solid electrolyte of this embodiment can be mixed with a positive electrode active material or a negative electrode active material to be used as a positive electrode layer or a negative electrode layer. The positive electrode active material or negative electrode active material, current collector, binder, conductive additive, etc. used in the positive electrode layer or negative electrode layer can be conventionally known substances.

[0119] The lithium-ion secondary battery includes a positive electrode layer, a solid electrolyte layer, and a negative electrode layer, and preferably includes the sulfide solid electrolyte of this embodiment in at least one layer selected from the above-mentioned positive electrode layer, solid electrolyte layer, and negative electrode layer.

[0120] The material used for the outer casing of a lithium-ion secondary battery can also be a known material. The shape of a lithium-ion secondary battery can also be a known shape, such as coin-shaped, sheet-like (film-like), folded, wound, bottomed cylindrical, button-shaped, etc., which can be appropriately selected according to the application.

[0121] Lithium-ion conductive crystals

[0122] The lithium-ion conductive crystal of this embodiment contains Li, P, S, and Ha as constituent elements. Here, Ha is at least one selected from F, Cl, Br, and I.

[0123] The lithium-ion conductive crystal of this embodiment exhibits diffraction peaks at least at 2θ = 12.4 ± 0.5°, 14.4 ± 0.5°, 20.2 ± 0.5°, 23.8 ± 0.5°, 29.7 ± 0.5°, and 31.4 ± 0.5° in its XRD pattern obtained by powder X-ray diffraction. Furthermore, the peak intensity of the diffraction peak at 2θ = 20.2 ± 0.5° is set to I. A The peak intensity of the diffraction peak with 2θ = 29.7 ± 0.5° is set as I. B At that time, I A / I B The indicated peak intensity ratio exceeds 1.0.

[0124] The lithium-ion conductive crystal in this embodiment is one form of the crystal constituting a high ion conductivity crystal phase in the above-mentioned "Sulfide Solid Electrolytes".

[0125] Specifically, the crystal constituting the aforementioned high ion conductivity phase contains Ha as a constituent element. Furthermore, in the XRD patterns obtained by powder X-ray diffraction, the crystal constituting the aforementioned high ion conductivity phase also exhibits diffraction peaks at 2θ = 12.4 ± 0.5°, 14.4 ± 0.5°, and 31.4 ± 0.5°, in addition to 2θ = 20.2 ± 0.5°, 23.8 ± 0.5°, and 29.7 ± 0.5°.

[0126] In this embodiment, the lithium-ion conductive crystal has a peak intensity of I at the diffraction peak of 2θ = 20.2 ± 0.5°. A Let the peak intensity of the diffraction peak at 2θ = 29.7 ± 0.5° be set as I. B At that time, I A / I B The peak intensity ratio indicates a value exceeding 1.0, which at least in this respect qualifies it as a novel crystal. Furthermore, the full width at half maximum (FWHM) of the diffraction peak at 2θ = 20.2 ± 0.5° is preferably 0.01 to 0.4°.

[0127] Other preferred embodiments of the lithium-ion conductive crystal in this embodiment are the same as the preferred embodiments of the high-ion conductive crystal phase in the above-mentioned "Sulfide Solid Electrolytes".

[0128] It should be noted that the lithium-ion conductive crystal of this embodiment has high lithium-ion conductivity, and is therefore suitable as a sulfide solid electrolyte. In this case, any sulfide solid electrolyte containing the aforementioned lithium-ion conductive crystal is acceptable. For example, it can be a sulfide solid electrolyte containing a glass before crystallization that serves as a precursor to the lithium-ion conductive crystal and the aforementioned lithium-ion conductive crystal; it can also be a sulfide solid electrolyte containing the aforementioned lithium-ion conductive crystal but not containing the aforementioned glass before crystallization; or it can be a sulfide electrolyte composed solely of the aforementioned lithium-ion conductive crystal.

[0129] Manufacturing Method of Sulfide Solid Electrolytes

[0130] In the method for manufacturing the sulfide solid electrolyte of this embodiment, such as Figure 1 As shown, the following processes 1 to 4 are sequentially included as steps S1 to S4.

[0131] Step S1: Process 1 of mixing raw materials to obtain a raw material mixture containing Li, P and S.

[0132] Step S2: Step 2 involves heating the raw material mixture obtained in step 1 to obtain a melt.

[0133] Step S3: Cooling and solidifying the melt obtained in step 2 to obtain the glass phase (step 3)

[0134] Step S4: Heating the glass phase obtained in step 3 to obtain a partially crystallized, highly ion-conducting crystalline phase from the glass phase in step 4.

[0135] The heating in step 2 and the cooling and curing in step 3 are carried out under normal pressure, and the cooling rate in the cooling and curing process is 100°C / second or higher.

[0136] In addition to the above, the heating for crystallization in step 4 is carried out at a temperature that is at or above the crystallization temperature of the glass phase obtained in step 3 (crystallization temperature - 15°C) for at least 1 minute.

[0137] Thus, a sulfide solid electrolyte comprising a glassy phase and a highly ion-conducting crystalline phase derived from that glassy phase is obtained. It should be noted that in this specification, "atmospheric pressure" refers to a pressure range of approximately (gauge pressure ± 15 kPa).

[0138] Furthermore, in step 1 above, by further mixing the raw materials to include Ha in the raw material mixture, the sulfide solid electrolyte described in the above-mentioned "Sulfide Solid Electrolytes" can be obtained. Here, Ha refers to at least one selected from F, Cl, Br, and I.

[0139] The following is a description of each process.

[0140] <Process 1>

[0141] Step S1 in this embodiment is process 1, which involves mixing raw materials to obtain a raw material mixture containing Li, P and S.

[0142] Specifically, raw materials containing Li, P, and S are mixed to obtain a raw material mixture. Furthermore, if it is desired to obtain a glass phase further containing Ha as a constituent element, in addition to mixing the raw materials containing Li, P, and S, a raw material containing Ha is further mixed to obtain a raw material mixture containing Li, P, S, and Ha. Here, Ha refers to at least one element selected from F, Cl, Br, and I.

[0143] Examples of raw materials containing lithium include lithium compounds such as lithium sulfide (Li₂S), lithium carbonate (Li₂CO₃), lithium sulfate (Li₂SO₄), lithium oxide (Li₂O), and lithium hydroxide (LiOH), as well as metallic lithium. One or more lithium-containing substances can be used.

[0144] From the viewpoint of obtaining a sulfide-based glassy phase, lithium sulfide is preferably used as the raw material containing Li. Furthermore, when the obtained sulfide solid electrolyte contains halogen elements, lithium halide (LiHa, where Ha is a halogen element) is also preferred as the raw material containing Li. Lithium halide will be discussed later.

[0145] Examples of raw materials containing phosphorus include phosphorus sulfides such as phosphorus pentasulfide (P2S5) and phosphorus trisulfide (P2S3), phosphorus compounds such as sodium phosphate (Na3PO4), and elemental phosphorus. Substances containing phosphorus can be used in one or more combinations.

[0146] From the viewpoint of preventing the presence of elements other than those constituting the target sulfide solid electrolyte, the raw material containing element P is preferably phosphorus sulfide, and more preferably phosphorus pentasulfide (P2S5).

[0147] Examples of raw materials containing sulfur include lithium sulfide (Li₂S), phosphorus trisulfide (P₂S₃), phosphorus pentasulfide (P₂S₅), and other phosphorus compounds containing phosphorus, as well as sulfur-containing compounds. Examples of sulfur-containing compounds include H₂S, CS₂, and iron sulfide (FeS, Fe₂S₃, FeS₂, Fe...). 1－x Bismuth sulfide (Bi2S3), copper sulfide (CuS, Cu2S, Cu, etc.), bismuth sulfide (Bi2S3), copper sulfide (CuS, Cu2S, Cu... 1－x (S, etc.). Substances containing the element S can be used with one element or in combination of two or more.

[0148] From the viewpoint of preventing the presence of elements other than those constituting the target sulfide solid electrolyte, the raw materials containing sulfur are preferably lithium sulfide or phosphorus sulfide, and phosphorus pentasulfide (P2S5) is more preferred as phosphorus sulfide. It should be noted that lithium sulfide is a compound that serves as both a raw material containing lithium and a raw material containing sulfur, and phosphorus sulfide is a compound that serves as both a raw material containing sulfur and a raw material containing phosphorus.

[0149] Examples of raw materials containing the element Ha include lithium fluoride (LiF), lithium chloride (LiCl), lithium bromide (LiBr), lithium iodide (LiI), lithium halides, phosphorus halides, phosphoryl halides, sulfur halides, sodium halides, and boron halides. Substances containing the element Ha can be used in one or more combinations.

[0150] From a reactivity point of view, the raw material containing Ha element is preferably lithium halide, more preferably LiCl, LiBr, or LiI, and even more preferably LiCl or LiBr.

[0151] Depending on the desired composition of the sulfide solid electrolyte, raw materials containing other elements can be further mixed to obtain a raw material mixture.

[0152] The other elements mentioned above, as described above, include, for example, Si, B, Ge, Al, O, Na, K, Mg, Ca, Sr, Ba, Y, Zr, Cr, Zn, Ga, Sn, and Sb. These other elements may also include, for example, Si, B, Ge, Al, Sn, and Sb. These Si, B, Ge, Al, Sn, and Sb are elements that may enter the P position during the crystallization of the sulfide-based glass phase.

[0153] Raw materials containing these other elements can be made from substances that are already known to the public.

[0154] For example, SiO2 and SiS2 are examples of raw materials containing the element Si. Among them, SiO2 is preferred from the viewpoint of lithium-ion conductivity. These compounds can be used alone or in combination of two or more.

[0155] Examples of raw materials containing element B include B₂O₃ and B₂S₃. Among these, B₂O₃ is more preferred from the viewpoint of improving the water resistance of glass. These compounds can be used alone or in combination of two or more.

[0156] Examples of raw materials containing the element Ge include GeO2, GeS, GeS2, and GeCl2. Among these, GeS2 and GeCl2 are preferred from the viewpoint of lithium-ion conductivity, with GeS2 being more preferred. These compounds can be used alone or in combination of two or more.

[0157] Examples of raw materials containing Al include Al₂S₃, Al₂O₃, and AlCl₃. From the viewpoint of lithium-ion conductivity and water resistance, Al₂S₃ and AlCl₃ are preferred, with Al₂S₃ being more preferred. These compounds can be used alone or in combination of two or more.

[0158] Examples of raw materials containing the element Sn include SnS, SnS2, SnO, SnO2, and SnCl2. Among these, SnS2 and SnCl2 are preferred from the viewpoint of lithium-ion conductivity, with SnS2 being more preferred. These compounds can be used alone or in combination of two or more.

[0159] Examples of raw materials containing Sb include Sb₂S₃, Sb₂O₃, Sb₂O₅, SbCl₃, and SbCl₅. From the viewpoint of lithium-ion conductivity and water resistance, Sb₂S₃ and SbCl₃ are preferred, and Sb₂S₃ is more preferred. These compounds can be used alone or in combination of two or more.

[0160] These raw materials are appropriately combined according to the desired composition of the glass phase of the sulfide system and the high ion conductivity crystalline phase derived from the glass phase of the sulfide system. Specifically, in order to obtain the sulfide solid electrolyte described in the above-mentioned "Sulfide Solid Electrolyte", the raw materials are mixed in such a way that the raw material mixture further includes Ha.

[0161] In addition, it is preferable to mix the raw materials such that the composition of the obtained glass phase and the high ion conductivity crystal phase from the glass phase satisfies Li: 30-50 at%, P: 5-15 at%, and S: 30-60 at%, and more preferably to mix the raw materials in a way that, in addition to the above composition, Ha: 1-12 at%.

[0162] By combining these raw materials, the crystal structure of the obtained high ion conductivity crystalline phase can also be determined.

[0163] In addition to the above, the preferred methods for obtaining the glass phase and the highly ion-conducting crystalline phase derived from the glass phase are the same as those for the preferred methods in "Sulfide Solid Electrolytes" above, specifically "Phase Composed of Sulfide Glass and Highly Ion-Conducting Crystalline Phase".

[0164] From the viewpoint of shortening the holding time during heating and melting in subsequent step 2, it is preferable to reduce the particle size of each raw material. Furthermore, if the particle size of the raw material is too large, it can sometimes affect the homogeneity of the glass phase or sulfide solid electrolyte; therefore, from this viewpoint, it is also preferable that the particle size of the raw material is relatively small. However, the manufacturing method of this embodiment offers excellent composition control. Therefore, even when using raw materials with particle sizes that might reduce homogeneity in conventional manufacturing methods, the manufacturing method of this embodiment can produce a more homogeneous glass phase or sulfide solid electrolyte.

[0165] Based on the above viewpoints, specifically, the particle size of each raw material is preferably less than 1 mm, more preferably less than 500 μm, further preferably less than 250 μm, even more preferably less than 100 μm, and particularly preferably less than 50 μm. Although smaller particle size is preferred, in practice the lower limit is around 0.1 μm, but it can also be greater than 1 μm, and even greater than 5 μm.

[0166] Furthermore, as described above, according to the manufacturing method of this embodiment, even when using raw materials with larger particle sizes, it is easy to obtain a homogeneous glass phase or sulfide solid electrolyte. Considering these factors, for example from the viewpoint of controlling manufacturing costs, the particle size of each raw material can be 10 μm or more, 100 μm or more, or even 250 μm or more.

[0167] Based on these, the particle size of each raw material is preferably 0.1 μm to 1 mm, more preferably 1 to 500 μm, even more preferably 5 to 250 μm, even more preferably 5 to 100 μm, and particularly preferably 5 to 50 μm. Furthermore, from the viewpoint of manufacturing cost, the particle size of each raw material is preferably 10 μm to 1 mm, more preferably 100 μm to 1 mm, and even more preferably 250 to 500 μm.

[0168] It should be noted that in this specification, the particle size of each raw material refers to the average particle size (D50) expressed as the median particle size obtained by measuring the particle size distribution using a Microtrac MT3300EXII laser diffraction particle size distribution analyzer and calculating the particle size distribution based on the obtained volume-based particle size distribution graph.

[0169] Raw material mixing can be achieved through media-based mixing methods such as mixing in a mortar and pestle, mixing using a planetary ball mill, media-free mixing such as a needle mill, powder mixer, or airflow mixing. Raw materials can also be mixed before heating to prevent crystallization.

[0170] <Process 2>

[0171] In this embodiment, step S2 is step 2, which involves heating the raw material mixture obtained in step 1 to obtain a melt.

[0172] There are no particular limitations on the specific methods for heating and melting the raw material mixture, except that heating is carried out under normal pressure.

[0173] The manufacturing method of this embodiment involves heating to melt the raw material mixture under atmospheric pressure, resulting in minimal deviation between the composition of the raw material mixture and the composition of the obtained sulfide-based glass phase and the highly ion-conducting crystalline phase derived from that glass phase, or the composition of the sulfide solid electrolyte. Furthermore, by performing the heating in an atmosphere containing sulfur, compositional deviations can be further suppressed. It should be noted that in the manufacturing method of this embodiment, the heating and melting are carried out under atmospheric pressure and in an atmosphere-controlled environment, thus eliminating the need for a sealed tube. However, the use of a sealed tube is not entirely excluded.

[0174] Here, the difference between a sealed tube and an environment under normal pressure and controlled atmosphere is that a sealed tube refers to a container where the pressure inside is in a vacuum state, i.e., less than (gauge pressure - 15 kPa). In contrast, an environment under normal pressure and controlled atmosphere refers to a container where the pressure inside is within the range of (gauge pressure ± 15 kPa) when heating and melting.

[0175] That is, the manufacturing method of this embodiment is carried out under normal pressure (gauge pressure ± 15 kPa) for the heating and melting of step 2. The composition ratio of the obtained glass phase or highly ion-conducting crystalline phase, expressed as [P / Li], is preferably 95 to 105% relative to the composition ratio of the raw material mixture at this time.

[0176] The pressure during the heating and melting process can be as low as (gauge pressure ± 15 kPa) at ambient pressure, preferably (gauge pressure ± 10 kPa), more preferably (gauge pressure ± 5 kPa), and even more preferably (gauge pressure ± 2 kPa).

[0177] Furthermore, relative to the [P / Li] composition ratio of the raw material mixture at this time, the [P / Li] composition ratio of the obtained glassy phase or highly ion-conducting crystalline phase is more preferably 95-105%, further preferably 97-103%, even more preferably 99-101%, and the closer to 100%, the more preferred. Here, the above composition ratio is preferably 95% or more, more preferably 97% or more, even more preferably 99% or more, and preferably 105% or less, more preferably 103% or less, and even more preferably 101% or less.

[0178] It should be noted that, regarding the [P / Li] ratio expressed relative to the raw material mixture, and the [P / Li] ratio expressed for the obtained glassy phase or highly ion-conducting crystalline phase, Li is a non-volatile element, while P is a volatile element. Therefore, comparing the [P / Li] ratio of the raw material mixture with that of the glassy phase or highly ion-conducting crystalline phase is suitable as an indicator of the compositional deviation between the composition of the raw material mixture and the composition of the obtained sulfide-based glassy phase or highly ion-conducting crystalline phase, or the composition of the sulfide solid electrolyte.

[0179] Examples of heat-resistant containers that incorporate a mixture of raw materials include carbon-based heat-resistant containers, containers containing oxides such as quartz, quartz glass, borosilicate glass, aluminosilicate glass, alumina, zirconium oxide, and mullite, containers containing nitrides such as silicon nitride and boron nitride, and containers containing carbides such as silicon carbide. Furthermore, these heat-resistant containers can have the main body formed from the aforementioned materials, or they can be containers with layers of carbon, oxides, nitrides, or carbides, such as carbon-coated quartz tubes.

[0180] The melting temperature when heating the raw material mixture varies depending on the raw materials used and the composition of the raw material mixture. For example, it is preferably 600–950°C, more preferably 630–850°C, and even more preferably 650–750°C. Here, from the viewpoint of reaction rate, the melting temperature is preferably 600°C or higher, more preferably 630°C or higher, and even more preferably 650°C or higher. In addition, from the viewpoint of suppressing compositional deviations caused by the volatilization of components, the above-mentioned melting temperature is preferably 950°C or lower, more preferably 850°C or lower, and even more preferably 750°C or lower.

[0181] The heating and melting time varies depending on the scale, preferably from 10 minutes to 10 hours, more preferably from 30 minutes to 9.5 hours, even more preferably from 45 minutes to 9 hours, and particularly preferably from 1 to 9 hours. From the viewpoint of ensuring a good reaction, the heating and melting time is preferably 10 minutes or more, more preferably 30 minutes or more, even more preferably 45 minutes or more, and particularly preferably 1 hour or more. Furthermore, from the viewpoint of productivity, the heating and melting time is preferably 10 hours or less, more preferably 9.5 hours or less, and even more preferably 9 hours or less.

[0182] The atmosphere inside the container during heating and melting is not particularly limited. For example, it can be a nitrogen atmosphere, an argon atmosphere, or a gaseous atmosphere containing sulfur. However, from the viewpoint of more appropriately suppressing compositional deviations, a gaseous atmosphere containing sulfur is preferred.

[0183] When using a gaseous atmosphere containing sulfur, sulfur gas, hydrogen sulfide gas, sulfur dioxide gas, etc. can be used as sources of sulfur. From the viewpoint of reactivity with raw materials, sulfur-containing gas is preferred.

[0184] Alternatively, as a gas containing sulfur (S), elemental sulfur powder can be added, and the elemental sulfur powder can be vaporized by heating during melting, thereby introducing a gas containing sulfur. The elemental sulfur powder can be added together with the raw materials when mixing them to obtain a raw material mixture, or it can be added separately after obtaining the raw material mixture. However, when the elemental sulfur powder is added together with the raw materials when obtaining the raw material mixture, the mass of the obtained raw material mixture does not include the mass of the aforementioned elemental sulfur powder.

[0185] As a gas containing sulfur, a gas containing sulfur produced by adding elemental sulfur powder can also be introduced at the same time as the aforementioned sulfur gas, hydrogen sulfide gas, sulfur dioxide gas, etc.

[0186] The gas containing sulfur is preferably used as a source of sulfur, for example, in the form of a mixture with an inert gas. The mixing ratio with the inert gas is arbitrary, and there is no particular limitation as long as the cumulative amount of sulfur relative to the mass of the raw material mixture is of a desired value.

[0187] Examples of inert gases mentioned above include nitrogen, argon, and helium. These gases can be used alone or in combination of two or more.

[0188] The dew point during heating and melting is preferably below -20°C, with no particular lower limit, but typically around -80°C. The oxygen concentration is preferably below 1000 ppm by volume.

[0189] In step 2, the complete dissolution of the raw material mixture can be confirmed by the absence of peaks originating from crystals in high-temperature X-ray diffraction measurements. Alternatively, it can be confirmed by heating the melt at a specified temperature and tilting it to check for fluidity.

[0190] <Process 3>

[0191] In this embodiment, step S3 is step 3, which involves cooling and solidifying the melt obtained in step 2 to obtain a glass phase.

[0192] Cooling and curing are carried out under normal pressure conditions. As mentioned above, normal pressure conditions refer to an atmosphere at a pressure of approximately ±15 kPa (gauge pressure).

[0193] The pressure during cooling and curing can be at atmospheric pressure (gauge pressure ± 15 kPa), preferably (gauge pressure ± 10 kPa), more preferably (gauge pressure ± 5 kPa), and even more preferably (gauge pressure ± 2 kPa).

[0194] The cooling rate during cooling and solidification is 100°C / second or higher, preferably 100 to 100,000°C / second, more preferably 500 to 50,000°C / second, and even more preferably 1,000 to 10,000°C / second. Here, by using a supercooling rate of 100°C / second or higher, which is faster than before, the proportion of the glass phase containing sulfide systems as constituent elements, such as Li, P, and S, can be, for example, 60% by mass or higher.

[0195] Compared to conventional sulfide-based glasses, this sulfide-based glass phase achieves higher lithium-ion conductivity, thus improving the lithium-ion conductivity of the sulfide solid electrolyte. Furthermore, by performing the aforementioned cooling and solidification under ambient pressure, the compositional deviation between the raw material mixture and the resulting glass phase, the highly ion-conducting crystalline phase derived from the glass phase, or the composition of the sulfide solid electrolyte can be reduced.

[0196] The cooling rate is 100°C / second or higher, but from the viewpoint of ease of glass formation, it is preferably 500°C / second or higher, more preferably 1000°C / second or higher. Furthermore, there is no particular upper limit to the cooling rate, but from the viewpoint of equipment capability, it is preferably 100,000°C / second or lower, more preferably 50,000°C / second or lower, and even more preferably 10,000°C / second or lower.

[0197] The ultra-rapid cooling described above can be achieved, for example, by using a rapid cooling twin roller.

[0198] Compared to conventional sulfide-based glasses, the glass phase of this sulfide system achieves higher lithium-ion conductivity. Furthermore, by performing the aforementioned cooling and solidification under ambient pressure, the compositional deviation between the raw material mixture and the resulting sulfide-based glass phase, as well as the composition of the high-ion-conductivity crystalline phase derived from this sulfide-based glass phase or the composition of the sulfide solid electrolyte, can be reduced.

[0199] <Process 4>

[0200] Step S4 of this embodiment is step 4, which involves heating the glass phase obtained in step 3 to obtain a high ion conductivity crystal phase in which a portion of the glass phase is crystallized.

[0201] The heating temperature in step 4, i.e. the temperature at which crystallization is carried out to obtain a highly ion-conducting crystalline phase, can be determined based on the crystallization temperature at which the glass phase becomes a highly ion-conducting crystalline phase.

[0202] Specifically, from the viewpoint of effectively promoting the above-mentioned crystallization, a temperature of (crystallization temperature - 15°C) or higher is preferred, which can be (crystallization temperature - 10°C) or higher, or a temperature of (crystallization temperature + 1°C) or higher. Furthermore, it is known that if heating is performed at a high temperature, crystals with low ionic conductivity will precipitate after the high ionic conductivity crystalline phase. Therefore, from the viewpoint of preventing the precipitation of crystals with low ionic conductivity, the above-mentioned crystallization temperature is preferably below the temperature at which such low ionic conductivity crystals precipitate, more preferably below (crystallization temperature + 20°C), and even more preferably below (crystallization temperature + 15°C).

[0203] That is, the crystallization temperature is preferably a temperature of (crystallization temperature - 15°C) or higher, more preferably a temperature of (crystallization temperature - 15°C) or higher and a temperature below which crystals with low ionic conductivity are precipitated. Alternatively, it can be a temperature of (crystallization temperature - 10°C) or higher and (crystallization temperature + 20°C), or a temperature of (crystallization temperature + 20°C) or higher and (crystallization temperature + 1°C) or lower and (crystallization temperature + 15°C).

[0204] It should be noted that the crystallization temperature in this specification refers to the temperature at the peak of the exothermic peak observed when the sulfide-based glass phase obtained in step 3, which can be considered a precursor to a sulfide solid electrolyte, is subjected to differential scanning calorimetry (DSC) at a heating rate of 5°C / min.

[0205] The heating time during crystallization is, for example, 1 minute or more, preferably 1 minute to 6 hours, more preferably 1 minute to 3 hours, further preferably 5 minutes to 2 hours, and even more preferably 10 minutes to 100 minutes. From the viewpoint of quality stability, the above heating time is preferably 1 minute or more, more preferably 5 minutes or more, and even more preferably 10 minutes or more. Furthermore, from the viewpoint of productivity, the above heating time is preferably 6 hours or less, more preferably 3 hours or less, further preferably 2 hours or less, and even more preferably 100 minutes or less.

[0206] By adjusting the heating temperature and heating time during crystallization, the proportion of the highly ion-conducting crystalline phase can be adjusted.

[0207] Examples of heating atmospheres during crystallization include nitrogen, argon, and dry air. From the perspective of not impairing ion conductivity, nitrogen or argon atmospheres are preferred.

[0208] The dew point during crystallization is preferably below -30°C.

[0209] In addition, the oxygen concentration during crystallization can be in a dry air environment, but from a safety point of view, it is preferred to be 5% by volume or less.

[0210] After heating, the electrolyte is cooled to room temperature at a rate of 1 to 10,000 °C / min, thereby obtaining the sulfide solid electrolyte of this embodiment.

[0211] The sulfide solid electrolyte obtained above can be directly used in at least one of the positive electrode layer, solid electrolyte layer and negative electrode layer, or the sulfide solid electrolyte after being crushed, dried or otherwise processed can be used depending on the application.

[0212] Example

[0213] The following examples illustrate the present invention in detail, but the present invention is not limited thereto.

[0214] Examples 1-4 are examples, and Examples 5-7 are comparative examples.

[0215] Experimental Examples

[0216] <Example 1: Melt quenching method>

[0217] Under a dry nitrogen atmosphere, to become Li 3.4 P 1.0 S 4.0 Br 0.34 Lithium sulfide powder (99.98% purity, manufactured by Sigma), phosphorus pentasulfide powder (99% purity, manufactured by Sigma), and lithium bromide powder (99.995% purity, manufactured by Sigma) were weighed according to the composition ratio of (Li: 38.9at%, P: 11.4at%, S: 45.8at%, Br: 3.9at%) and mixed in a mortar to obtain the raw material mixture (step 1).

[0218] Under a nitrogen atmosphere containing sulfur powder (99.998% purity, manufactured by Sigma) as the sulfur source and with a dew point below -50°C, the resulting raw material mixture is placed in a carbon container and then placed in an electric furnace inside a glove box. The mixture is heated for 1 hour at a pressure of gauge pressure +1 kPa and a temperature of 750°C to obtain a completely melted molten material (step 2).

[0219] Next, the front end of the heated container is melted, and the molten liquid flows out onto the twin rollers, where it is cooled to room temperature at a cooling rate of 3000°C / second, thus obtaining the glass phase (step 3). The pressure at this time is (gauge pressure + 1 kPa), and the cooling rate is adjusted by the outflow rate of the molten liquid, the gap between the twin rollers, and the rotation speed.

[0220] The glass phase obtained above is heated at 210°C for 10 minutes under a nitrogen atmosphere to crystallize a portion of the glass phase (step 4), and then cooled to room temperature at a cooling rate of 300°C / min to obtain a sulfide solid electrolyte containing a glass phase and a highly ion-conducting crystal phase.

[0221] It should be noted that the glass phase obtained above was subjected to DSC measurement at a heating rate of 5°C / min, and the temperature at the peak of the exothermic peak, i.e. the crystallization temperature, was confirmed to be 223°C.

[0222] <Examples 2 and 3: Melt quenching method>

[0223] The cooling rate in step 3 was set to 8000°C / second (Example 2) or 10000°C / second (Example 3). Otherwise, a sulfide solid electrolyte containing a glassy phase and a highly ion-conducting crystalline phase was obtained in the same manner as in Example 1. The crystallization temperature of the glassy phase obtained in step 3 was confirmed to be 217°C (Example 2) or 215°C (Example 3).

[0224] <Example 4: Melt-cooling method>

[0225] Based on the composition ratio, it becomes Li 3.4 P 1.0 S 4.0 Cl 0.1 Br 0.2 Lithium sulfide powder (99.98% purity, manufactured by Sigma-Aldrich), phosphorus pentasulfide powder (99% purity, manufactured by Sigma-Aldrich), lithium bromide powder (99.995% purity, manufactured by Sigma-Aldrich), and lithium chloride powder (99.995% purity, manufactured by Sigma-Aldrich) were weighed in the manner of the composition ratio (Li: 39.1at%, P: 11.5at%, S: 46.0at%, Cl: 1.1at%, Br: 2.3at%) to obtain a raw material mixture. Otherwise, the process was carried out in the same manner as in Example 1 to obtain a sulfide solid electrolyte containing a glassy phase and a highly ion-conducting crystalline phase.

[0226] It should be noted that the crystallization temperature of the glass phase obtained in step 3 is confirmed to be 219°C.

[0227] Example 5: Mechanical Grinding Method

[0228] Perform step 1 in the same manner as in Example 1 to obtain a mixture of raw materials.

[0229] Next, the resulting raw material mixture was further mixed using a planetary ball mill (Fritsch, P-7) to obtain the glassy phase (steps 2'+3'). The mixing using the planetary ball mill was performed using zirconia balls with a particle size of 4 mm and a zirconia jar, under a nitrogen atmosphere at 400 rpm for 20 hours. The dew point was maintained below -70°C during operation.

[0230] The glass phase obtained above is heated at 210°C for 10 minutes under a nitrogen atmosphere to crystallize a portion of the glass phase (step 4). Then, it is cooled to room temperature at a cooling rate of 300°C / min to obtain a sulfide solid electrolyte containing a glass phase and a highly ion-conducting crystalline phase.

[0231] It should be noted that the crystallization temperature of the glass phase mentioned above is 207°C.

[0232] <Example 6: Mechanical Grinding Method>

[0233] Perform step 1 in the same manner as in Example 4 to obtain a mixture of raw materials.

[0234] Next, steps 2'+3' and 4 are performed in the same manner as in Example 5 to obtain a sulfide solid electrolyte containing a glassy phase and a highly ion-conducting crystalline phase.

[0235] It should be noted that the crystallization temperature of the aforementioned glass phase is 210℃.

[0236] <Example 7: Melt-cooling method>

[0237] The cooling rate in step 3 was set to 50°C / second, and otherwise carried out in the same manner as in Example 1, to obtain a sulfide solid electrolyte. In step 3, impurity crystals were obtained, and the desired glassy phase was not obtained, so the crystallization temperature of the glassy phase could not be determined.

[0238] Therefore, even if the temperature is increased to 210°C for 10 minutes in the subsequent step 4, a sulfide solid electrolyte containing both a glassy phase and a highly ion-conducting crystalline phase cannot be obtained.

[0239] Evaluation: Glassy Phase

[0240] In each example, the sulfide solid electrolyte obtained in step 3 or step 2'+3', consisting of a glassy phase or a crystalline phase of impurities, is weighed in a glove box and dissolved in an alkaline aqueous solution, and the composition of each element is analyzed.

[0241] Specifically, ICP emission spectroscopy analysis was performed on P and S (device: Hitachi High Tech Science, model PS3520UVDDII).

[0242] Li was analyzed using atomic absorption spectrometry (Apparatus: Hitachi High Tech, model ZA3300, CsCl was added at a solution concentration of 0.1% during Li determination).

[0243] Br and Cl were analyzed by ion chromatography (Apparatus: Thermo Fisher Scientific, model ICS-2100 (column: AS11HC), with a small amount of H2O2 added and diluted with ultrapure water for determination).

[0244] Through the above operations, the composition of the sulfide solid electrolyte, which consists of a glassy phase or a crystalline phase of impurities, was confirmed.

[0245] In addition to the above, for Example 7, the sulfide solid electrolyte was pulverized using a mortar and passed through a 100 μm sieve to prepare a powder of solid electrolyte with an average particle size D50 of about 20 μm, which was used as a sample.

[0246] X-ray diffraction (XRD) was performed using a Rigaku SmartLab apparatus under the following conditions: X-ray source: CuKα rays (λ = 1.5418 Å); tube voltage: 45 kV; tube current: 200 mA; scanning angle: 10–100°; scanning speed: 5° / min; step size: 0.01° / step; in a non-exposed atmospheric environment. Additionally, silicon powder was added as an internal standard during XRD measurements, and Rietwald analysis was performed to determine the crystallinity (wt%).

[0247] Evaluation: Sulfide Solid Electrolytes

[0248] <Composition ratio, content ratio>

[0249] The sulfide solid electrolytes obtained in Examples 1 to 6 were pulverized in a mortar and passed through a 100 μm sieve to prepare a powder of solid electrolyte precursor with an average particle size D50 of about 20 μm, which was used as a sample.

[0250] Then, XRD measurements were performed under the same conditions as when the sulfide solid electrolyte composed of impurity crystalline phases in Example 7 was used as the sample.

[0251] In the obtained XRD pattern, the value of 2θ for the observed diffraction peak was determined. Additionally, the half-width at half-maximum (FWHM) of the diffraction peak at 2θ = 20.2 ± 0.5° was determined, and the peak intensity of the diffraction peak at 2θ = 20.2 ± 0.5° was set as I. A The peak intensity of the diffraction peak with 2θ = 29.7 ± 0.5° is set as I. B I at that time A / I B The peak intensity ratio is represented.

[0252] Furthermore, by analyzing the obtained XRD patterns, the composition ratio and content of the high ion conductivity phase were determined.

[0253] Here, it can be determined that the composition ratio of the phase composed of sulfide-based glass is the same as that of the high ion conductivity crystalline phase. However, for the sake of caution, it is compared with the composition ratio obtained through the evaluation of the glass phase. The results confirm that, relative to the composition ratio of the high ion conductivity crystalline phase, any component of the composition ratio of the glass phase before step 3 is within ±20%.

[0254] The results are shown in Table 1. It should be noted that no diffraction peak of 2θ = 20.2 ± 0.5° was observed in Example 7, and therefore it is marked as "-" in Table 1.

[0255] It should be noted that the XRD patterns of the sulfide solid electrolytes obtained in Examples 2 and 5 are shown in [the figures]. Figure 2 and Figure 3 .

[0256] <Lithium-ion conductivity>

[0257] The sulfide solid electrolytes obtained in each example were pulverized using a mortar and pestle, and then passed through a 100 μm sieve to produce powder with an average particle size (D50) of about 20 μm, which was used as a sample.

[0258] The above sample was pressed into powder under a pressure of 380 MPa and used as the test sample. The electrochemical impedance spectroscopy (EIS) was performed using a potentiostat / galvanostat (VSP) manufactured by Bio-Logic Sciences Instruments. The test conditions were: frequency: 100 Hz–1 MHz, voltage: 100 mV, and temperature: 25 °C. The lithium-ion conductivity was determined from the obtained Nyquist plot. The results are shown in Table 1, “σ…”. Li＋ (mS / cm)

[0259] [Table 1]

[0260]

[0261] Based on the above results, it can be seen that although the sulfide solid electrolytes of Examples 1-3 have the same composition as the sulfide solid electrolyte of Example 5, they can also achieve high lithium-ion conductivity. The narrow half-maximum width (HWHM) of the diffraction peaks observed at 2θ = 20.2 ± 0.5° in the sulfide solid electrolytes of Examples 1-3 indicates high crystallinity. Furthermore, a good correlation between the HWHM and lithium-ion conductivity was confirmed. The same trend was confirmed based on the results of Examples 4 and 6.

[0262] Furthermore, in Examples 1-3 and Examples 5, and Examples 4 and 6, although the compositions of the high ion conductivity crystal phases are the same, the peak intensity I... A With peak intensity I B The ratio of I A / IB The size relationship is reversed, with values ​​exceeding 1.0 (Examples 1-3, 4) and less than 1.0 (Examples 5, 6). The high ionic conductivity crystal phase in the sulfide solid electrolyte of this embodiment is a novel crystal that has not existed previously.

[0263] Furthermore, as shown in Examples 1 to 3, when the cooling rate is above a certain value, the slower the cooling rate, the higher the lithium-ion conductivity. This is believed to be because the slow cooling rate allows for a certain degree of ordering in the glass state, resulting in better crystallinity after heating for crystallization, a narrower half-width, and higher lithium-ion conductivity.

[0264] In Example 7, because the cooling rate during solidification was below 100°C / second, the desired glassy phase was not obtained, and instead, impurity crystalline phases precipitated. Therefore, Example 7 exhibited low lithium-ion conductivity when used as a sulfide solid electrolyte.

[0265] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. This application is based on Japanese Patent Application No. 2023-168393, filed on September 28, 2023, the contents of which are incorporated herein by reference.

Claims

1. A sulfide solid electrolyte comprising a crystalline phase and a glassy phase, The glass phase comprises a phase consisting of sulfide-based glasses, wherein Li, P, S, and Ha are constituent elements. The Ha is at least one selected from F, Cl, Br and I. The crystalline phase comprises a highly ion-conducting crystalline phase derived from the sulfide-based glass. The high ion conductivity crystalline phase exhibits diffraction peaks at at least 2θ = 20.2 ± 0.5°, 23.8 ± 0.5°, and 29.7 ± 0.5° in the XRD pattern obtained by powder X-ray diffraction. The half-width at half-maximum (WHM) of the diffraction peak at 2θ = 20.2 ± 0.5° is 0.01–0.4°.

2. The sulfide solid electrolyte according to claim 1, wherein, In the XRD pattern of the high ion conductivity crystalline phase, the peak intensity of the diffraction peak at 2θ = 20.2 ± 0.5° is set as I. A The peak intensity of the diffraction peak with 2θ = 29.7 ± 0.5° is set as I. B At that time, I A / I B The indicated peak intensity ratio exceeds 1.

0.

3. The sulfide solid electrolyte according to claim 1 or 2, wherein, The content of the high ion conductivity crystalline phase in the sulfide solid electrolyte is 50% by mass or more.

4. The sulfide solid electrolyte according to claim 1 or 2, wherein, The phase composed of the sulfide glass and the highly ion-conducting crystalline phase have the following compositions: Li: 30-50 at%, P: 5-15 at%, S: 30-60 at%, and Ha: 1-12 at%.

5. The sulfide solid electrolyte according to claim 1 or 2, wherein, The highly ion-conducting crystalline phase further exhibits a diffraction peak in the XRD pattern at at least one location selected from 2θ = 12.4 ± 0.5°, 14.4 ± 0.5°, and 31.4 ± 0.5°.

6. A lithium-ion conductive crystal comprising Li, P, S, and Ha as constituent elements. The Ha is at least one selected from F, Cl, Br and I. In the XRD patterns obtained by powder X-ray diffraction, diffraction peaks were observed at least at 2θ = 12.4 ± 0.5°, 14.4 ± 0.5°, 20.2 ± 0.5°, 23.8 ± 0.5°, 29.7 ± 0.5°, and 31.4 ± 0.5°. Let the peak intensity of the diffraction peak at 2θ = 20.2 ± 0.5° be set as I. A The peak intensity of the diffraction peak with 2θ = 29.7 ± 0.5° is set as I. B At that time, I A / I B The indicated peak intensity ratio exceeds 1.

0.

7. A method for manufacturing a sulfide solid electrolyte, comprising the following steps: The raw materials are mixed to obtain a raw material mixture containing Li, P and S. Heating the raw material mixture yields a melt. The molten material is cooled and solidified to obtain the glass phase, and Heating the glass phase yields a portion of it crystallized into a highly ion-conducting crystalline phase. The heating and cooling solidification used to obtain the melt are carried out under normal pressure conditions. The cooling rate during the cooling and solidification process is above 100°C / second. The heating used to obtain the highly ion-conducting crystalline phase is performed at a temperature at or above the crystallization temperature of the glass phase (the crystallization temperature - 15°C) for at least 1 minute. The sulfide solid electrolyte comprises the glass phase and the highly ion-conducting crystalline phase.

8. The method for manufacturing a sulfide solid electrolyte according to claim 7, wherein, The raw material mixture further comprises Ha. The Ha is at least one selected from F, Cl, Br and I.

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