Glass, crystalline glass, sulfide solid electrolyte, electrode mixture, solid electrolyte layer, and lithium ion secondary battery

Abstract

The present invention relates to a glass which contains Li and P as elements constituting a cationic component, contains S as an element constituting an anionic component, and has a composition satisfying, in atomic%, 30-42% of Li and 5-16% of P, a glass transition point of 110-300 DEG C, and a lithium ion conductivity at 25 DEG C of 2 mS / cm or more.

Description

Technical Field

[0001] This invention relates to glass, crystal glass, sulfide solid electrolyte, electrode mixture, solid electrolyte layer and lithium-ion secondary battery. 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 concerns about leakage and fire necessitated larger casings for safety reasons. Furthermore, improvements were desired to address issues such as short battery life and narrow operating temperature range.

[0004] In contrast, 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. Compared to oxide ions, sulfide ions, which constitute sulfide solid electrolytes, have higher polarizability and exhibit higher ionic conductivity.

[0006] On the other hand, sulfide solid electrolytes are highly reactive with water in the air and readily produce hydrogen sulfide. Therefore, Patent Document 1 discloses a sulfide glass-ceramic solid electrolyte formed by crystallizing a portion of a sulfide-based glass with Li2S / P2S5 / LiI = 63 / 21 / 16 or 52 / 17 / 31 and a sulfide-based glass with Li2S / P2S5 / LiBr = 64 / 21 / 14 as a solid electrolyte with excellent water resistance and high ionic conductivity.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2018-049834 Summary of the Invention

[0010] The sulfide-based glass described in Patent Document 1 is manufactured by a mechanical grinding method that uses a ball mill or bead mill to mechanically react the raw materials.

[0011] However, according to the research of the inventors, it has been found that glass obtained by mechanical grinding is prone to retaining residues of excessive sulfur or unreacted raw materials, which contribute to the generation of hydrogen sulfide. Furthermore, when using glass in sulfide solid electrolytes, higher lithium-ion conductivity is desired.

[0012] Therefore, the object of the present invention is to provide a glass exhibiting high lithium-ion conductivity, suppressing hydrogen sulfide generation, and possessing excellent water resistance. Furthermore, the object is to provide a crystalline glass in which a portion of the aforementioned glass is crystallized, useful as a sulfide solid electrolyte. Moreover, the object is to provide a sulfide solid electrolyte, an electrode mixture, a sulfide solid electrolyte layer, and a lithium-ion secondary battery comprising the aforementioned crystalline glass.

[0013] Through repeated and in-depth research, the inventors discovered that by using methods such as heating and melting of raw materials or mixtures thereof, and then rapidly cooling them, even compositional regions that were previously difficult to vitrify can be vitrified, resulting in glass with no residue and high homogeneity. Therefore, the aforementioned glass exhibits low hydrogen sulfide production and excellent water resistance. Furthermore, by manufacturing the glass, various anionic and cationic components can be selected, enabling the achievement of high lithium-ion conductivity.

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

[0015] [1] A glass containing Li and P as constituent cationic elements,

[0016] It contains sulfur (S) as an element constituting the anion.

[0017] The composition, expressed in atomic percent, satisfies:

[0018] Li: 30-42%, and

[0019] P: 5-16%;

[0020] The glass transition point is 110–300℃.

[0021] The lithium-ion conductivity at 25℃ is above 2 mS / cm.

[0022] [2] The glass according to [1] above further comprises at least one element selected from Sn, Sb, Si, Ge, Ga, Al, B, C, Mg, Ca, Sr and Ba as constituting the above-mentioned cation component.

[0023] [3] The glass according to [1] or [2] above, wherein it further comprises at least one element selected from F, Cl, Br, I, O, Se, N and C as constituting the above-mentioned anionic component.

[0024] [4] A crystalline glass comprising a crystalline phase from any one of the glasses described in [1] to [3] above.

[0025] [5] A sulfide solid electrolyte comprising the crystalline glass described in [4] above.

[0026] [6] An electrode mixture comprising the sulfide solid electrolyte described in [5] above.

[0027] [7] A solid electrolyte layer comprising the sulfide solid electrolyte described in [5] above.

[0028] [8] A lithium-ion secondary battery comprising the sulfide solid electrolyte described in [5] above.

[0029] According to the present invention, a glass exhibiting high lithium-ion conductivity, suppressing hydrogen sulfide generation, and possessing excellent water resistance can be obtained. Furthermore, by crystallizing at least a portion of this glass, a crystalline glass useful as a sulfide solid electrolyte can be obtained. Therefore, a solid electrolyte comprising the aforementioned crystalline glass can achieve excellent battery characteristics when used in solid electrolyte layers, electrode mixtures, or lithium-ion secondary batteries. Attached Figure Description

[0030] Figure 1 This is a flowchart illustrating the glass manufacturing method of this embodiment.

[0031] Figure 2 This is a flowchart illustrating the method for manufacturing the crystal glass according to this embodiment. Detailed Implementation

[0032] The present invention will now be described in detail, but the present invention is not limited to the following embodiments and can be implemented in any way without departing from the spirit of the present invention. Furthermore, the symbol “~” indicating a numerical range is used to mean that the values ​​described before and after it are both lower and upper limits.

[0033] "Glass"

[0034] The glass of this embodiment contains Li and P as elements constituting the cationic component, and S as an element constituting the anionic component.

[0035] The composition of the above-mentioned glass, expressed in atomic percent, satisfies the following.

[0036] Li: 30-42%, and

[0037] P: 5-16%.

[0038] If a conventional mechanical grinding method is used to process the raw material mixture that satisfies the above composition, the resulting solid is an amorphous phase but does not have a glass transition point. However, in this embodiment, glass can be obtained by melting and rapidly cooling the raw material mixture.

[0039] By producing glass as described above, it is possible to achieve high homogeneity without residues such as residual sulfur or unreacted raw materials, and high water resistance with suppressed hydrogen sulfide production.

[0040] Furthermore, unlike mechanical grinding methods, various anionic and cationic compositions can be selected regardless of the hardness of the raw materials to obtain the desired glass. Therefore, high lithium-ion conductivity can also be achieved.

[0041] The glass of this embodiment contains Li and P as elements constituting the cation composition, but may further contain at least one element selected from Sn, Sb, Si, Ge, Ga, Al, B, C, Mg, Ca, Sr, and Ba. From the viewpoint of water resistance, it is preferable to contain at least one element selected from Sb, Si, and Sn. Furthermore, from the viewpoint of ionic conductivity, it is preferable to contain Al and B.

[0042] The elements constituting the cationic components are described. It should be noted that the content of each element in the glass is expressed in atomic percent (atomic%).

[0043] Li is essential for ion conduction in solid electrolytes. The Li content in the glass is 30-42%, preferably 33-41%. From the viewpoint of lithium-ion conductivity, the above content is 30% or more, preferably 33% or more, and more preferably 35% or more. Furthermore, from the viewpoint of vitrification, the above content is 42% or less, preferably 41% or less, and more preferably 40% or less.

[0044] Phosphorus (P) is an essential element for forming the glass network. P-S bonds exhibit high resistance to both oxidation and reduction in sulfides. Therefore, as a solid electrolyte, it possesses a wide potential window and excellent electrochemical stability. The P content in the glass is 5–16%, preferably 6–14%. From the viewpoint of vitrification, this content is 5% or more, preferably 6% or more, and more preferably 7% or more. Furthermore, from the viewpoint of lithium-ion conductivity, this content is 16% or less, preferably 14% or less, and more preferably 12% or less.

[0045] In this embodiment, when the glass contains Si as a constitutive cationic element, Si has the effect of increasing the viscosity of the molten liquid and promoting vitrification. The Si content in the glass is preferably 0 to 10%, more preferably 0.5 to 10%, and even more preferably 2 to 9%. Here, from the viewpoint of appropriately obtaining the effects brought about by Si, the Si content is preferably 0.5% or more, more preferably 2% or more. Furthermore, from the viewpoint of electrochemical stability, the Si content is preferably 10% or less, more preferably 9% or less.

[0046] In this embodiment, when the glass contains Sn as a constitutive cationic element, Sn has the effect of increasing the viscosity of the melt and promoting vitrification. The Sn content in the glass is preferably 0-10%, more preferably 0.1-10%, and even more preferably 0.5-8%. Here, from the viewpoint of appropriately obtaining the effects brought about by Sn, the Sn content is preferably 0.1% or more, more preferably 0.5% or more. Furthermore, from the viewpoint of electrochemical stability, the Sn content is preferably 10% or less, more preferably 8% or less.

[0047] In this embodiment, when the glass contains Sb as a constitutive cation component, Sb has the effect of increasing the viscosity of the molten liquid and promoting vitrification. The Sb content in the glass is preferably 0-10%, more preferably 0.1-8%, and even more preferably 1-5%. From the viewpoint of appropriately obtaining the effects brought about by Sb, the Sb content is preferably 0.1% or more, more preferably 1% or more. Furthermore, from the viewpoint of lithium-ion conductivity, the Sb content is preferably 10% or less, more preferably 8% or less, and even more preferably 5% or less.

[0048] In this embodiment, when the glass contains Ge as a constitutive cation element, Ge has the effect of promoting increased lithium-ion conductivity. The Ge content in the glass is preferably 0-10%, more preferably 0.1-8%, and even more preferably 1-5%. From the viewpoint of appropriately obtaining the effects brought about by Ge, the Ge content is preferably 0.1% or more, more preferably 1% or more. Furthermore, from the viewpoint of glass formability, the Ge content is preferably 10% or less, more preferably 8% or less, and even more preferably 5% or less.

[0049] In this embodiment, when Ga is included as a constitutive cation element in the glass, Ga has the effect of promoting increased lithium-ion conductivity. The Ga content in the glass is preferably 0-10%, more preferably 0.1-8%, and even more preferably 1-5%. From the viewpoint of appropriately obtaining the effects brought about by Ga, the Ga content is preferably 0.1% or more, more preferably 1% or more. Furthermore, from the viewpoint of glass formability, the Ga content is preferably 10% or less, more preferably 8% or less, and even more preferably 5% or less.

[0050] In this embodiment, when the glass contains Al as a constitutive cationic element, Al has the effect of increasing the viscosity of the molten liquid and promoting vitrification. The Al content in the glass is preferably 0-10%, more preferably 0.1-8%, and even more preferably 1-5%. From the viewpoint of appropriately obtaining the effects brought about by Al, the Al content is preferably 0.1% or more, more preferably 1% or more. Furthermore, from the viewpoint of lithium-ion conductivity, the Al content is preferably 10% or less, more preferably 8% or less, and even more preferably 5% or less.

[0051] In this embodiment, when the glass contains boron (B) as a constitutive cationic element, B has the effect of increasing the viscosity of the molten liquid and promoting vitrification. The content of B in the glass is preferably 0-10%, more preferably 0.1-8%, and even more preferably 1-5%. From the viewpoint of appropriately obtaining the effects brought about by B, the content of B is preferably 0.1% or more, more preferably 1% or more. Furthermore, from the viewpoint of lithium-ion conductivity, the content of B is preferably 10% or less, more preferably 8% or less, and even more preferably 5% or less.

[0052] In this embodiment, when the glass contains carbon (C) as a constitutive cationic element, C has the effect of improving glass-forming ability. The C content in the glass is preferably 0-10%, more preferably 0.1-8%, and even more preferably 1-5%. From the viewpoint of appropriately obtaining the effects brought about by C, the C content is preferably 0.1% or more, more preferably 1% or more. Furthermore, from the viewpoint of lithium-ion conductivity, the C content is preferably 10% or less, more preferably 8% or less, and even more preferably 5% or less.

[0053] In this embodiment, when the glass contains an alkaline earth metal element as a constitutive cationic component, the alkaline earth metal element has the effect of improving glass-forming ability. Examples of alkaline earth metal elements include one or more selected from Mg, Ca, Sr, and Ba.

[0054] The content of each alkaline earth metal element in the glass is preferably 0 to 10%, more preferably 0.1 to 8%, and even more preferably 1 to 5%, when alkaline earth metal elements are included. Here, from the viewpoint of appropriately obtaining the effects brought about by alkaline earth metal elements, the content of each alkaline earth metal element is preferably 0.1% or more, more preferably 1% or more. Furthermore, from the viewpoint of lithium-ion conductivity, the content of each alkaline earth metal element is preferably 10% or less, more preferably 8% or less, and even more preferably 5% or less.

[0055] Furthermore, the total content of alkaline earth metal elements in the glass is preferably 0 to 20%, more preferably 0.2 to 18% when alkaline earth metal elements are included, and even more preferably 1 to 15%. Here, the above-mentioned total content is preferably 0.2% or more, more preferably 1% or more, and preferably 20% or less, more preferably 18% or less, and even more preferably 15% or less.

[0056] The glass of this embodiment contains sulfur (S) as an element constituting the anionic component, but may further contain at least one element selected from F, Cl, Br, I, O, Se, N, and C. From the viewpoint of improving ionic conductivity, it is preferable to contain at least one element selected from F, Cl, Br, and I; more preferably, it contains at least one element selected from Cl, Br, and I; and even more preferably, it contains I. Furthermore, from the viewpoint of improving vitrification ability, it is preferable to contain one or more elements selected from O, Se, N, and C.

[0057] The elements constituting the anionic composition are described. It should be noted that the content of each element in the glass is expressed in atomic percent (atomic%).

[0058] S is an element that forms P-S bonds with P and is essential for the formation of the glass phase. The S content in the glass is preferably 30-60%, more preferably 33-55%, and even more preferably 37-50%. From the viewpoint of vitrification, the above content is preferably 30% or more, more preferably 33% or more, and even more preferably 37% or more. Furthermore, from the viewpoint of lithium-ion conductivity, the above content is preferably 60% or less, more preferably 55% or less, and even more preferably 50% or less.

[0059] In the case where the glass of this embodiment contains a halogen element (X) as an element constituting anionic components, X is an element that contributes to high lithium-ion conductivity.

[0060] The total content of X in the glass is preferably 0-20%, more preferably 1-20% when X is included, and can be 1-12% or 2-10%. From the viewpoint of appropriately obtaining the effects brought about by X, the total content when X is included is preferably 1% or more, more preferably 2% or more, further preferably 3% or more, and particularly preferably 6% or more. Furthermore, from the viewpoint of preventing the precipitation of lithium halide crystals, the total content of X is preferably 20% or less, more preferably 19% or less, and further preferably 17% or less. It should be noted that in conventional mechanical grinding methods, compositional regions with high X content are particularly difficult to vitrify. However, according to the research of the inventors, it has been newly discovered that by using methods such as heating-based melting and quenching of raw materials or mixtures thereof, even in such compositional regions, high lithium-ion conductivity can be achieved. Therefore, even compositions with a total X content of approximately 20% can be vitrified. However, in the glass of this embodiment, in the case where lithium halide crystals are easily precipitated, the total content of X can be 12% or less, or 10% or less.

[0061] In this composition, the total content of Br and I in the aforementioned total X preferably accounts for 50% or more, more preferably 70% or more, and can be 100%, i.e., composed solely of Br and I. Furthermore, the content 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. However, it is not excluded that only Cl is included as X.

[0062] In the case where the glass of this embodiment contains F as a constituent anionic element, the F content in the glass is preferably 0.1% to 20%, and can be 0.1% to 10%, or 0.5% to 5%. Here, the aforementioned F content is preferably 0.1% or more, more preferably 0.5% or more, further preferably 3% or more, and particularly preferably 6% or more. Furthermore, the aforementioned F content is preferably 20% or less, more preferably 19% or less, and further preferably 17% or less. In the case where lithium fluoride crystals readily precipitate, the aforementioned F content can be 10% or less, or 5% or less.

[0063] In the case where the glass of this embodiment contains Cl as a constituent anionic component, the Cl content in the glass is preferably 0.1% to 20%, preferably 0.1% to 10%, or 0.5% to 5%. Here, the Cl content is preferably 0.1% or more, more preferably 0.5% or more, further preferably 3% or more, and particularly preferably 6% or more. Furthermore, the Cl content is preferably 20% or less, more preferably 19% or less, and further preferably 17% or less. In cases where lithium chloride crystals readily precipitate, the Cl content can be 10% or less, or 5% or less.

[0064] In the case where the glass of this embodiment contains Br as a constituent anionic component, the Br content in the glass is preferably 0.1% to 20%, and can be 0.1% to 10%, or 1% to 8%. Here, the Br content is preferably 0.1% or more, more preferably 1% or more, further preferably 3% or more, and particularly preferably 6% or more. Furthermore, the Br content is preferably 20% or less, more preferably 19% or less, and further preferably 17% or less. In the case where lithium bromide crystals readily precipitate, the Br content can be 10% or less, or 8% or less.

[0065] In the case where the glass of this embodiment contains iodine (I) as a constituent element of the anionic component, I is particularly helpful in improving ionic conductivity, and is therefore preferred. The content of I in the glass is preferably 0.1% to 20%, but can be 0.1% to 10%, 1% to 8%, or 2% to 6%. Here, the aforementioned I content is preferably 0.1% or more, more preferably 1% or more, further preferably 2% or more, even more preferably 3% or more, and particularly preferably 6% or more. Furthermore, the aforementioned I content is preferably 20% or less, more preferably 19% or less, and even more preferably 17% or less. In cases where lithium iodide crystals readily precipitate, or from the viewpoint of improving vitrification, the aforementioned I content can be 10% or less, 8% or less, or 6% or less.

[0066] In this embodiment, when the glass contains O as an element constituting anionic components, O has the effect of improving ionic conductivity. The content of O in the glass is preferably 0-5%, more preferably 0.1-4%, and even more preferably 0.5-3%. Here, from the viewpoint of appropriately obtaining the effects brought about by O, the content of O is preferably 0.1% or more, more preferably 0.5% or more. Furthermore, from the viewpoint of water resistance, the content of O is preferably 5% or less, more preferably 4% or less, and even more preferably 3% or less.

[0067] In this embodiment, when the glass contains Se as a constituent anionic element, Se has the effect of improving ionic conductivity. The Se content in the glass is preferably 0-5%, more preferably 0.1-4%, and even more preferably 0.5-3%. Here, from the viewpoint of appropriately obtaining the effects brought about by Se, the Se content is preferably 0.1% or more, more preferably 0.5% or more. Furthermore, from the viewpoint of water resistance, the Se content is preferably 5% or less, more preferably 4% or less, and even more preferably 3% or less.

[0068] In this embodiment, when the glass contains nitrogen (N) as a constituent element of the anionic component, N has the effect of improving ionic conductivity. The N content in the glass is preferably 0-5%, more preferably 0.1-4%, and even more preferably 0.5-3%. Here, from the viewpoint of appropriately obtaining the effects brought about by N, the N content is preferably 0.1% or more, more preferably 0.5% or more. Furthermore, from the viewpoint of water resistance, the N content is preferably 5% or less, more preferably 4% or less, and even more preferably 3% or less.

[0069] In this embodiment, when the glass contains carbon (C) as a constituent element of the anionic component, C has the effect of improving ionic conductivity. The C content in the glass is preferably 0-5%, more preferably 0.1-4%, and even more preferably 0.5-3%. Here, from the viewpoint of appropriately obtaining the effects brought about by C, the C content is preferably 0.1% or more, more preferably 0.5% or more. Furthermore, from the viewpoint of water resistance, the C content is preferably 5% or less, more preferably 4% or less, and even more preferably 3% or less.

[0070] It should be noted that carbon (C) can be an element constituting both cations and anions. When sulfur (S) is in excess relative to glass, C can be identified as an element constituting cations; when sulfur is deficient, C can be identified as an element constituting anions.

[0071] The glass of this embodiment may further contain other elements in addition to the elements constituting the above-mentioned cationic or anionic components, without impairing the effects of the present invention.

[0072] Other elements that can be cited include Na, K, Y, Zr, Cr, Zn, Fe, Co, Ti, and Mn.

[0073] The total content of the other elements mentioned above in the glass of this embodiment, expressed in atomic percent, can be, for example, 0 to 5%, and when other elements are included, it can be 0.1 to 4%, or 0.5 to 3%. Here, the total content can be 0.1% or more, or 0.5%, and also 4% or less, or 3% or less.

[0074] The glass composition of this embodiment only needs to satisfy Li: 30-42% and P: 5-16% in atomic percent. In addition, it is preferable to satisfy one or more of S: 30-60%, X: 1-20%, Si: 1-10% and Sn: 0.1-10%, preferably two or more, and more preferably three or more.

[0075] Furthermore, in addition to satisfying the above-mentioned X: 1 to 20%, it is more preferable to satisfy at least one of Br: 0.1 to 19% and I: 0.1 to 19%.

[0076] It should be noted that the glass composition of this embodiment can satisfy one or more of the following: S: 30-60%, X: 1-12%, Si: 1-10%, and Sn: 0.1-10%, or two or more, or three or more.

[0077] In addition, if X: 1 to 12% is satisfied, at least one of Br: 0.1 to 10% and I: 0.1 to 10% can also be satisfied.

[0078] The methods for determining the constituent elements and their contents (composition ratios) of the glass in this embodiment vary depending on the element. For example, P, S, Sn, Sb, Si, Ge, Ga, Al, Mg, Ca, Sr, Ba, and Se are determined by ICP emission spectroscopy analysis, Li and B are determined by atomic absorption spectroscopy, X is determined by ion chromatography, and C, O, and N are determined by XPS (X-ray photoelectron spectroscopy) analysis, etc. Details of each analysis are described in the items of the embodiments described later.

[0079] The glass in this embodiment has a glass transition point of 110–300°C, preferably 130–300°C, more preferably 140–290°C, and particularly preferably 150–280°C. Here, in this embodiment, glass with a glass transition point can be produced by melting and rapidly cooling a mixture of raw materials.

[0080] From the viewpoint of improving the formability and stability of glass, the glass transition point is 110°C or higher, preferably 130°C or higher, more preferably 140°C or higher, and particularly preferably 150°C or higher. Furthermore, from the viewpoint of formability, the glass transition point is 300°C or lower, preferably 290°C or lower, and more preferably 280°C or lower.

[0081] It should be noted that the glass transition point in this specification is the temperature of the first inflection point of the DSC graph obtained by differential scanning calorimetry (DSC), and can be adjusted by the glass composition and the cooling rate of the melt.

[0082] The crystallization temperature of the glass in this embodiment is not particularly limited, but is preferably 130–400°C, more preferably 140–400°C, and particularly preferably 150–370°C. From the viewpoint of formability, the crystallization temperature is preferably 130°C or higher, more preferably 140°C or higher, and particularly preferably 150°C or higher. Furthermore, from the viewpoint of glass stability, the crystallization temperature is preferably 400°C or lower, more preferably 370°C or lower.

[0083] When the glass transition point of the glass in this embodiment is set as Tg and the crystallization temperature is set as Tc, the temperature difference (Tc-Tg) is preferably 10 to 200°C, more preferably 20 to 180°C. From the viewpoint of glass stability, this difference is preferably 10°C or more, more preferably 20°C or more. Furthermore, from the viewpoint of productivity, this difference is preferably 200°C or less, more preferably 180°C or less.

[0084] The lithium-ion conductivity of the glass in this embodiment at 25°C when it is pressed into powder at 380 MPa is 2 mS / cm or higher, preferably 3 mS / cm or higher, and the higher the conductivity, the more preferred.

[0085] It should be noted that the lithium-ion conductivity in this specification is determined by pressing the powder used as the sample into a powder body at 380 MPa and using it as the test sample through AC impedance spectroscopy. Specifically, the test frequency is set to 100 Hz to 1 MHz, the test voltage to 100 mV, and the test temperature to 25 °C. The AC impedance of the test sample is measured, and the value obtained from the resulting Nyquist plot is taken as the lithium-ion conductivity.

[0086] The aforementioned lithium-ion conductivity can be adjusted by the glass composition, reducing thermal unevenness during the rapid cooling of the molten raw material mixture, and adjusting the cooling rate. In particular, the glass of this embodiment is obtained by melting and rapidly cooling the raw material mixture, rather than by the conventional mechanical grinding method. As a result, the vitrification region is widened, and it is easier to include multiple desired anionic and cationic components. Consequently, a composition capable of achieving high lithium-ion conductivity can be adopted.

[0087] The amount of H2S generated when the glass of this embodiment is exposed to an atmosphere with a dew point of -30°C for 1 hour is preferably 10 mL / g or less, more preferably 4 mL / g or less, even more preferably 1 mL / g or less, particularly preferably 0.1 mL / g or less, and the less the better.

[0088] It should be noted that the more specific measurement conditions for the above-mentioned H2S generation are as follows.

[0089] First, the sample was prepared into a powder with an average particle size of 10–20 μm by passing it through a 100 μm sieve. Then, the amount of hydrogen sulfide (H2S) generated was measured when 10 mg of the powder was exposed to an atmosphere humidified to a dew point of -30 °C for 1 hour, and the total amount was taken as the amount of H2S generated.

[0090] Crystalline Glass

[0091] The crystallized glass of this embodiment is obtained by heat-treating the glass described in the above-mentioned "Glass" to crystallize at least a portion of it.

[0092] That is, the crystalline glass of this embodiment comprises a crystalline phase derived from the glass described in the aforementioned "Glass". Furthermore, it may optionally further comprise an amorphous phase, which in this case comprises a phase composed of the glass described in the aforementioned "Glass".

[0093] Here, the phase derived from the aforementioned glass refers to the crystalline phase formed by crystallizing the glass through heat treatment. Except for cases where the crystallized glass consists solely of a 100% crystallized crystalline phase, the glass from which the crystalline phase originates can be inferred based on the crystal structure and mass ratio of the crystalline phase, as well as the overall composition of the crystallized glass.

[0094] Specifically, for the crystalline phase, the crystal structure and mass ratio of the crystalline phase are calculated by performing Rietveld analysis on the XRD pattern obtained by powder X-ray diffraction (XRD). On the other hand, the overall composition of the crystalline glass is determined in the same way as the above-mentioned methods for determining the constituent elements and their contents (composition ratios) of the glass, using ICP emission spectroscopy, atomic absorption spectroscopy, ion chromatography, XPS, etc., depending on the type of element.

[0095] Then, by subtracting the composition of the crystalline phase from the overall composition of the crystallized glass by mass ratio, the composition and amount of the amorphous phase can be calculated. If the composition of this amorphous phase is considered to be the composition of the glass before crystallization, and is equivalent to the glass of this embodiment described in the aforementioned "Glass" document, then the crystallized glass can be determined to be equivalent to the crystallized glass involved in this embodiment.

[0096] The composition of the glass prior to crystallization to obtain crystalline glass is referred to as the parent composition. The parent composition of the crystalline glass in this embodiment is the same as that described in the above-mentioned "Glass". That is, it can be said that the composition of the amorphous phase of the crystalline glass in this embodiment is the same as the parent composition.

[0097] Furthermore, the composition of the crystal phase in this embodiment differs from the above-mentioned parent composition by a maximum of about 30%, and P tends to decrease.

[0098] The above-mentioned crystal phase can adopt the sulfur-silicon region type II or LGPS type crystal structure.

[0099] The crystalline glass of this embodiment exhibits a higher lithium-ion conductivity than the known value of lithium-ion conductivity when using its crystal structure, suggesting that it is a crystalline glass obtained by crystallizing the aforementioned "glass" which was not obtained by conventional mechanical grinding but by melting and rapidly cooling a mixture of raw materials.

[0100] The proportion (crystallinity) of the crystalline phase in the crystalline glass of this embodiment is preferably 10 to 100% by mass, more preferably 20 to 90% by mass, and even more preferably 30 to 80% by mass. Here, from the viewpoint of lithium-ion conductivity, the above-mentioned crystallinity is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more. In addition, from the viewpoint of productivity, the above-mentioned crystallinity is preferably 100% by mass or less, more preferably 90% by mass or less, and even more preferably 80% by mass or less.

[0101] It should be noted that the crystallinity of the crystal glass in this embodiment can be 100% by mass, and can consist of only crystalline phases. The crystallinity is determined by the following operation: the crystal glass is made into powder, and powder X-ray diffraction (XRD) is performed together with the crystal powder used as an internal standard to determine the proportion of crystals, which is then subtracted from 100% by mass, thereby performing Rietveld analysis.

[0102] Since the glass before crystallization in this embodiment has high lithium-ion conductivity, the lithium-ion conductivity of the crystallized glass in this embodiment is also high, and it can be appropriately used as a solid electrolyte.

[0103] That is, when the crystal glass of this embodiment is pressed into powder at 380 MPa, the lithium-ion conductivity at 25°C is preferably 2 mS / cm or more, more preferably 3 mS / cm or more, and the higher the better.

[0104] Sulfide Solid Electrolytes

[0105] The sulfide solid electrolyte of this embodiment includes the crystal glass described in the above-mentioned "Crystallized Glass".

[0106] The constituent elements and composition ratios of the crystal glass described above can be considered to be substantially the same as those of the sulfide solid electrolyte involved in this embodiment. Therefore, the preferred embodiment of the constituent elements and composition ratios of the sulfide solid electrolyte described above can be replaced by the preferred embodiment of the constituent elements and composition ratios of the crystal glass described above.

[0107] However, the sulfide solid electrolyte of this embodiment may also contain other phases besides the crystal glass described above.

[0108] The average particle size (D50) of the sulfide solid electrolyte in this embodiment is preferably 0.5 to 100 μm, more preferably 0.8 to 80 μm, and even more preferably 1 to 50 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 100 μm or less, more preferably 80 μm or less, and even more preferably 50 μm or less. Furthermore, from the viewpoint of powder processing, the above-mentioned average particle size is preferably 0.5 μm or more, more preferably 0.8 μm or more, and even more preferably 1 μm or more.

[0109] 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, bead mills, and jet mills. Furthermore, wet grinding is preferred for coarse grinding.

[0110] The sulfide solid electrolyte of this embodiment is suitable as an electrolyte for lithium-ion secondary batteries. When used in a lithium-ion secondary battery, the sulfide solid electrolyte is formed into a solid electrolyte layer together with other components such as binders, as needed. That is, the solid electrolyte layer of this embodiment contains the aforementioned sulfide solid electrolyte.

[0111] The binder and other components that make up the solid electrolyte layer can be made from substances that are already known.

[0112] 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.

[0113] The sulfide solid electrolyte of this embodiment can be mixed with a positive or negative electrode active material to serve as an electrode additive for the positive or negative electrode layer. That is, the electrode additive of this embodiment contains the aforementioned sulfide solid electrolyte.

[0114] The positive or negative active material, current collector, binder, conductive additive, etc. used in the positive or negative electrode layer can be any previously known material.

[0115] The lithium-ion secondary battery of this embodiment includes a positive electrode layer, a solid electrolyte layer, and a negative electrode layer. Preferably, at least one layer selected from the positive electrode layer, the solid electrolyte layer, and the negative electrode layer contains the sulfide solid electrolyte of this embodiment. That is, the lithium-ion secondary battery of this embodiment includes the sulfide solid electrolyte described above.

[0116] The outer casing of a lithium-ion secondary battery can also be made of materials that are already known. The shape of a lithium-ion secondary battery can also be made of materials that are already known, such as coin-shaped, sheet-like (film-like), folded, wound, bottomed cylindrical, button-shaped, etc., which can be appropriately selected according to the application.

[0117] Manufacturing methods for glass and crystal glass

[0118] like Figure 1 As shown, the glass manufacturing method of this embodiment includes the following steps 1 and 2 as steps S1 and S2.

[0119] Step S1: The process of heating a mixture of raw materials containing Li, P and S to obtain a melt.

[0120] Step S2: Step 2 involves cooling and solidifying the molten material obtained in step 1 to obtain glass.

[0121] like Figure 2 As shown, the method for manufacturing crystallized glass in this embodiment includes the following steps 1 to 3 as steps S1 to S3. Here, steps S1 and S2 are the same as steps S1 and S2 in the glass manufacturing method of this embodiment described above.

[0122] Step S1: The process of heating a mixture of raw materials containing Li, P and S to obtain a melt.

[0123] Step S2: Step 2 involves cooling and solidifying the molten material obtained in step 1 to obtain glass.

[0124] Step S3: Heat-treat the glass obtained in step 2 to crystallize a portion of it, thus obtaining crystallized glass in step 3.

[0125] The heating in step 1 and the cooling in step 2 are carried out under normal pressure, and the cooling rate during solidification is 100°C / second or higher. Cooling is performed in a way that ensures uniform cooling of the melt without thermal unevenness. This eliminates residues such as residual sulfur or unreacted raw materials, homogenizes the material, and thus achieves good water resistance. Furthermore, the wide vitrification range and increased compositional freedom enable high lithium-ion conductivity.

[0126] It should be noted that in this instruction manual, "normal pressure" refers to a pressure range of approximately (gauge pressure ± 15 kPa).

[0127] In step 1 above, the glass obtained contains Li and P as elements constituting the cationic component, and S as an element constituting the anionic component. The raw materials are mixed in such a way that their composition, expressed in atomic percent, satisfies Li: 30-42% and P: 5-16%.

[0128] The following describes each process.

[0129] <Process 1>

[0130] Step S1 in this embodiment is a process 1 in which the raw materials are mixed to obtain a raw material mixture containing Li, P and S, and then heated.

[0131] Specifically, a raw material containing Li, a raw material containing P, and a raw material containing S are mixed to obtain a raw material mixture. Furthermore, if it is desired to obtain a glass further containing X as a constituent element, a raw material containing X is further mixed in addition to the raw materials containing Li, P, and S to obtain a raw material mixture containing Li, P, S, and X. Here, X is at least one element selected from F, Cl, Br, and I.

[0132] 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 type of lithium-containing raw material can be used, or two or more can be used in combination.

[0133] From the viewpoint of obtaining sulfide-based glasses, lithium sulfide is preferably used as the raw material containing Li. Furthermore, if the obtained glass contains halogen elements, lithium halide (LiX, where X is a halogen element) is also preferred as the raw material containing Li. Lithium halide will be discussed later.

[0134] 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. One type of raw material containing phosphorus can be used, or two or more types can be used in combination.

[0135] From the viewpoint of preventing the presence of elements other than those constituting the target glass, raw materials containing element P are preferably phosphorus sulfide, and more preferably phosphorus pentasulfide (P2S5).

[0136] In addition, when using the aforementioned elemental phosphorus as a raw material containing the element P, examples include yellow phosphorus, red phosphorus, purple phosphorus, and black phosphorus.

[0137] Examples of raw materials containing sulfur include lithium sulfide (Li₂S), phosphorus trisulfide (P₂S₃), phosphorus pentasulfide (P₂S₅), and other phosphorus sulfides, as well as other sulfur compounds containing phosphorus and other 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.). Raw materials containing the element S can use one type or a combination of two or more types.

[0138] From the viewpoint of preventing the presence of elements other than those constituting the target glass, lithium sulfide and phosphorus sulfide are preferred raw materials containing sulfur, with phosphorus pentasulfide (P2S5) being more preferred as phosphorus sulfide. It should be noted that lithium sulfide is a compound that can be used as both a raw material containing lithium and a raw material containing sulfur, and phosphorus sulfide is a compound that can be used as both a raw material containing sulfur and a raw material containing phosphorus.

[0139] Examples of raw materials containing element X 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. One type of raw material containing element X can be used, or two or more types can be used in combination.

[0140] From a reactivity point of view, the raw material containing element X is preferably lithium halide, more preferably LiCl, LiBr, or LiI, and even more preferably LiBr or LiI.

[0141] Other raw materials can be further mixed to obtain a raw material mixture based on the desired glass composition.

[0142] For example, if the glass further comprises at least one element selected from Sn, Sb, Si, Ge, Ga, Al, B, C, Mg, Ca, Sr, and Ba as a constitutive cation, a raw material containing these elements may be used. This raw material is not limited to compounds but may also be a single metal.

[0143] If the glass further comprises, in addition to X mentioned above, at least one element selected from O, Se, N, and C as a constitutive anionic component, raw materials containing these elements may be used. This raw material is not limited to compounds but may also be a single metal.

[0144] If the glass further contains the other elements mentioned above, raw materials containing Na, K, Y, Zr, Cr, Zn, Fe, Co, Ti, Mn, etc., can be used. It should be noted that when the obtained glass is further processed into a crystalline glass, Si, B, Ge, Al, Sn, and Sb are elements that can enter the P position.

[0145] These other raw materials can be derived from substances that are already known in the past.

[0146] For example, Si, SiO2, SiS2, and SiS are examples of raw materials containing the element Si. Among these, SiO2 is more preferred from the viewpoint of lithium-ion conductivity. These compounds can be used alone or in combination of two or more.

[0147] Examples of raw materials containing the element Sn include Sn, SnS, SnS2, SnO, SnO2, and SnCl2. Among these, SnS2 and SnCl2 are preferred from the viewpoint of lithium-ion conductivity, and SnS2 is more preferred. These compounds can be used alone or in combination of two or more.

[0148] Examples of raw materials containing Sb include Sb, Sb₂S₃, Sb₂O₃, Sb₂O₅, SbCl₃, and SbCl₅. Among these, Sb₂S₃ and SbCl₃ are preferred from the viewpoint of lithium-ion conductivity and water resistance, and Sb₂S₃ is more preferred. These compounds can be used alone or in combination of two or more.

[0149] Examples of raw materials containing the element Ge include Ge, GeO2, GeS, GeS2, and GeCl2. Among these, GeS2 and GeCl2 are preferred from the viewpoint of lithium-ion conductivity, and GeS2 is more preferred. These compounds can be used alone or in combination of two or more.

[0150] Examples of raw materials containing the element Al include Al, Al₂S₃, Al₂O₃, and AlCl₃. Among these, Al₂S₃ and AlCl₃ are preferred from the viewpoint of lithium-ion conductivity and water resistance, and Al₂S₃ is more preferred. These compounds can be used alone or in combination of two or more.

[0151] Examples of raw materials containing element B include B, B₂O₃, and B₂S₃. Among these, B₂O₃ is preferred from the viewpoint of water resistance of glass. These compounds can be used alone or in combination of two or more.

[0152] These raw materials are appropriately combined according to the desired composition of the glass. Specifically, in order to obtain the glass and crystalline glass described in the above-mentioned "Glass" and "Crystallized Glass", the raw materials are mixed in a manner that includes Li, P and S, and at least satisfies the following conditions: Li: 30-42% and P: 5-16%.

[0153] Apart from the above, the preferred methods for obtaining glass and crystal glass are the same as those described in the above-mentioned "Glass" and "Crystal Glass".

[0154] From the viewpoint of shortening the holding time during heating to obtain the melt, 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; therefore, from this viewpoint, a certain degree of small particle size is also preferable. However, the manufacturing method of this embodiment offers excellent composition control. Therefore, even when using raw materials with particle sizes that, for example, might reduce homogeneity in conventional manufacturing methods, the manufacturing method of this embodiment can produce more homogeneous glass.

[0155] 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. Smaller particle size is preferred, but the lower limit is actually around 0.1 μm, and can be greater than 1 μm or greater than 5 μm.

[0156] Furthermore, as described above, according to the manufacturing method of this embodiment, even when using raw materials with larger particle sizes, homogeneous glass can be easily obtained. Considering this, for example from the viewpoint of reducing 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.

[0157] Therefore, 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.

[0158] It should be noted that in this specification, the particle size of each raw material refers to the average particle size (D50) expressed by the median particle size obtained from the volume-based particle size distribution map obtained by measuring the particle size distribution using a Microtrac MT3300EXII laser diffraction particle size distribution analyzer.

[0159] Raw materials can be mixed in various ways, such as using a mortar and pestle, a planetary ball mill, a needle mill, a powder mixer, or an air-jet mixer. Raw materials can be amorphized by mixing before heating.

[0160] There are no particular limitations on the specific method for heating a mixture of raw materials to obtain a melt, except that the heating is carried out under normal pressure.

[0161] The manufacturing method of this embodiment involves heating the raw material mixture under atmospheric pressure to melt it, resulting in a small compositional deviation between the composition of the raw material mixture and the composition of the obtained glass. Furthermore, by performing the above heating in a gas atmosphere containing sulfur, compositional deviations can be further suppressed. It should be noted that in the manufacturing method of this embodiment, the heating for obtaining the melt is performed under a controlled atmosphere at atmospheric pressure, thus eliminating the need for pipe sealing. However, pipe sealing is not excluded.

[0162] Here, the difference between a sealed container and an environment with controlled atmosphere under normal pressure is that a sealed container means that the pressure inside the container is in a vacuum state, that is, less than (gauge pressure - 15 kPa). In contrast, an environment with controlled atmosphere under normal pressure means that the pressure inside the container during heating is within the range of (gauge pressure ± 15 kPa).

[0163] That is, the manufacturing method of this embodiment is carried out under normal pressure conditions (gauge pressure ± 15 kPa) to heat the material to obtain the melt.

[0164] The heating pressure mentioned above 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).

[0165] It should be noted that when heating the raw material mixture, for example, based on the fact that Li is a non-volatile element and P is a volatile element, it is preferable to adjust the addition ratio of Li and P in the raw material mixture in a way that achieves the desired content ratio of Li and P as a glass.

[0166] It should be noted that the manufacturing method of this embodiment can be either batch or continuous.

[0167] Examples of heat-resistant containers for holding raw material mixtures include carbon-based heat-resistant containers, heat-resistant containers containing oxides such as quartz, quartz glass, borosilicate glass, aluminosilicate glass, alumina, zirconium oxide, and mullite, heat-resistant containers containing nitrides such as silicon nitride and boron nitride, and heat-resistant containers containing carbides such as silicon carbide. Furthermore, these heat-resistant containers can be formed as a single unit from the aforementioned materials, or they can be containers with layers of carbon, oxides, nitrides, and carbides, such as carbon-coated quartz tubes.

[0168] The heating temperature for obtaining the melt of 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 heating 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 component volatilization, the above-mentioned heating temperature is preferably 950°C or lower, more preferably 850°C or lower, and even more preferably 750°C or lower.

[0169] The heating 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 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 time is preferably 10 hours or less, more preferably 9.5 hours or less, and even more preferably 9 hours or less.

[0170] The atmosphere inside the container during heating 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.

[0171] 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 the raw material mixture, sulfur-containing gas is preferred.

[0172] Alternatively, as a gas containing sulfur, it can be introduced by adding elemental sulfur powder and heating it to vaporize the powder. 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, if the elemental sulfur powder is added together with the raw materials when obtaining the raw material mixture, the mass of the resulting raw material mixture does not include the mass of the elemental sulfur powder.

[0173] As a gas containing sulfur, a gas containing sulfur by adding elemental sulfur powder can be introduced at the same time as the aforementioned sulfur gas, hydrogen sulfide gas, sulfur dioxide gas, etc.

[0174] 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 introduced relative to the mass of the raw material mixture is at a desired value.

[0175] Examples of inert gases mentioned above include nitrogen, argon, and helium. These gases can be used alone or in combination of two or more.

[0176] The dew point during heating is preferably below -20°C, with no particular lower limit, typically around -80°C. The oxygen concentration is preferably below 1000 ppm by volume.

[0177] In step 1, the melting of the raw material mixture can be confirmed by the absence of peaks originating from crystals in high-temperature X-ray diffraction measurements. Alternatively, its fluidity can be confirmed by heating it at a specified temperature and tilting the melt.

[0178] <Process 2>

[0179] In this embodiment, step S2 is step 2, which involves cooling and solidifying the molten material obtained in step 1 to obtain glass.

[0180] Cooling and curing are carried out under normal pressure conditions. Here, normal pressure conditions, as mentioned above, refer to an atmosphere at a pressure of approximately (gauge pressure ± 15 kPa).

[0181] 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).

[0182] The cooling rate during cooling and solidification is 100°C / second or higher, preferably 100 to 100,000°C / second, more preferably 200 to 50,000°C / second, and even more preferably 300 to 10,000°C / second. Here, it has been found that by using ultra-rapid cooling at a rate of 100°C / second or higher, which is faster than before, even compositions that previously precipitated crystals can be solidified into glass. This significantly increases the freedom of composition selection, allowing for the selection of compositions exhibiting high lithium-ion conductivity.

[0183] Furthermore, by performing the aforementioned cooling and solidification in a manner that uniformly cools the melt without thermal unevenness, a higher lithium-ion conductivity than conventional glass can be achieved. Consequently, the lithium-ion conductivity of the crystalline glass obtained by heat-treating this glass can also be improved. Additionally, by performing the aforementioned cooling and solidification under normal pressure, the compositional deviation between the raw material mixture and the obtained glass can be reduced.

[0184] The cooling rate is 100°C / second or higher, and from the viewpoint of ease of glass formation, it is preferably 200°C / second or higher, more preferably 300°C / second or higher. Furthermore, there is no particular upper limit to the cooling rate; from the viewpoint of equipment capacity, 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.

[0185] The ultra-rapid cooling described above can be achieved, for example, by using a rapid cooling twin roller.

[0186] The glass obtained above can be used directly as a sulfide solid electrolyte without undergoing crystallization in step 3. Furthermore, the sulfide solid electrolyte can be further used in sulfide solid electrolyte layers, electrode mixtures, and lithium-ion secondary batteries. Additionally, the glass described above can be glass that has undergone crushing, drying, etc., depending on its intended use.

[0187] <Process 3>

[0188] Step S3 in this embodiment is a process 3 in which the glass obtained above is subjected to heat treatment to crystallize at least a portion of it to obtain crystallized glass.

[0189] The resulting crystalline glass can be used as a sulfide solid electrolyte, and further used in sulfide solid electrolyte layers, electrode mixtures, and lithium-ion secondary batteries. Alternatively, crystalline glass can be obtained by crushing, drying, etc., depending on the intended application.

[0190] The temperature in the above heat treatment can be determined based on the crystallization temperature of the glass.

[0191] Specifically, from the viewpoint of effectively promoting crystallization, the temperature in the above-mentioned heat treatment is preferably a temperature of (crystallization temperature - 15°C) or higher, which can be a temperature of (crystallization temperature - 10°C) or higher, a temperature of (crystallization temperature) or higher, or a temperature of (crystallization temperature + 1°C) or higher. Furthermore, from the viewpoint of preventing the precipitation of crystals other than the desired crystalline phase during heating at high temperatures, the crystallization temperature is preferably, for example, a temperature of (crystallization temperature + 20°C) or lower, and more preferably a temperature of (crystallization temperature + 15°C) or lower.

[0192] It should be noted that the crystallization temperature in this specification refers to the temperature of the peak of the heating peak observed when the glass obtained in step 2 is heated at a rate of 10°C / minute using differential scanning calorimetry (DSC).

[0193] 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.

[0194] By adjusting the heating temperature and time during crystallization, the proportion of crystalline phases in the crystal glass can be adjusted.

[0195] Examples of heating atmospheres during crystallization include vacuum, nitrogen, argon, and dry air. Among these, nitrogen and argon atmospheres are preferred from the viewpoint of not impairing lithium-ion conductivity.

[0196] The dew point during crystallization is preferably below -30°C.

[0197] In addition, the oxygen concentration during crystallization can be in a dry air environment, and from a safety point of view, it is preferably 5% by volume or less.

[0198] After heating, the glass is cooled to room temperature at a rate of, for example, 1 to 10,000 °C / min, thereby obtaining the crystal glass of this embodiment.

[0199] The crystalline glass obtained above is suitable for use as a sulfide solid electrolyte. Furthermore, the sulfide solid electrolyte can be further used in sulfide solid electrolyte layers, electrode mixtures, and lithium-ion secondary batteries. Additionally, the crystalline glass can be a crystalline glass that has undergone crushing, drying, etc., depending on its intended use.

[0200] Example

[0201] The following examples illustrate the present invention in detail, but the present invention is not limited thereto.

[0202] Examples 1 to 5 and Examples 9 to 17 are examples, Examples 6 to 8 are comparative examples, and Example 18 is a reference example.

[0203] Experimental Examples

[0204] 〈Example 1~Example 17〉

[0205] Under a dry nitrogen atmosphere, lithium sulfide powder (Albemarle, 99.9% purity) and phosphorus pentasulfide powder (Perimeter, 95-100% purity), as well as any SiS2 powder (Mitsuwa Chemicals, 99% purity), SnS2 powder (Mitsuwa Chemicals, 99.5% purity), lithium chloride powder (Sigma-Aldrich, 99.995% purity), lithium bromide powder (Sigma-Aldrich, 99.995% purity), and lithium iodide powder (Tokyo Chemical Industry, 99.9% purity) were weighed separately in the composition ratios listed in Table 1, and mixed in a mortar to obtain a raw material mixture.

[0206] The obtained raw material mixture was placed in a carbon container under a nitrogen atmosphere containing sulfur powder (Sigma-Aldrich, purity 99.998%) as the sulfur source and with a dew point below -50°C. The container was then placed in an electric furnace inside a glove box and heated for 1 hour at a pressure of gauge pressure +1 kPa and a temperature of 750°C to obtain a melt (step 1).

[0207] Next, the front end of the container is heated to melt it, and the molten material is flowed out onto the double rollers at a rate that does not produce uneven temperature. It is then cooled to room temperature at a cooling rate of 500°C / second to obtain glass (step 2). The pressure at this time is (gauge pressure + 1 kPa), and the cooling rate is adjusted by the outflow rate of the molten material, the gap between the double rollers, and the rotation speed.

[0208] 〈Example 18〉

[0209] Lithium sulfide powder (Albemarle, 99.9% purity), phosphorus pentasulfide powder (Perimeter, 95-100% purity), SiS2 powder (Mitsuwa Chemicals, 99% purity), and lithium chloride powder (Sigma-Aldrich, 99.995% purity) were weighed separately according to the composition ratios listed in Table 1, and mixed in a mortar to obtain a raw material mixture. In a nitrogen-atmospheric glove box, 1 g of the above raw material mixture was placed together with 500 φ4 mm zirconia balls into a zirconia jar, which was then completely sealed. The mixture was mechanically ground using a planetary ball mill (Fritsch, P-7) at 510 rpm for 20 hours to obtain the sample of Example 18.

[0210] "evaluate"

[0211] <Glass Composition>

[0212] The obtained glass was weighed in a glove box and dissolved in an alkaline aqueous solution, and the composition of each element was analyzed.

[0213] Specifically, ICP emission spectroscopy analysis was performed on P, S, Sn, Sb, Si, Ge, Ga, Al, Mg, Ca, Sr, Ba, and Se (device: Hitachi High-Tech Science, model PS3520UVDDII).

[0214] Li was analyzed using atomic absorption spectrometry (apparatus: Hitachi High-Tech Corporation, model ZA3300, CsCl was added at a solution concentration of 0.1% during Li determination).

[0215] Cl, Br, and I were analyzed using 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).

[0216] The results are shown in Table 1, “Glass Composition (Atomic %)”. It should be noted that in all examples, the composition of the obtained glass did not deviate significantly from that of the raw material mixture.

[0217] <Physical Property: Lithium-ion Conductivity>

[0218] The obtained glass was crushed in a mortar 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.

[0219] The above sample was pressed into powder at 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 the "σ" section of the "Physical Properties" item in Table 1. 25 (mS / cm)

[0220] <Material Properties: Glass Transition Point>

[0221] The obtained glass was measured using differential scanning calorimetry (DSC) at 10 °C / min. The temperature at the first inflection point of the obtained DSC graph was determined as the glass transition point. The results are shown in the "Tg (°C)" section of Table 1 under "Physical Properties". It should be noted that this measurement was also performed on the sample of Example 18, and the results showed that it did not have a glass transition point.

[0222] <Physical Properties: H2S Production>

[0223] The obtained glass was pulverized in a mortar and then passed through a 100 μm sieve to prepare a powder with an average particle size (D50) of 10–20 μm, which was used as a sample. The amount of hydrogen sulfide (H2S) produced was then monitored by exposing 10 mg of this sample to an atmosphere conditioned to a dew point of -30°C for 1 hour. The amount produced per 1 g of sample was calculated as the H2S production amount (mL / g). The results are shown in the "H2S Production Amount (mL / g)" section of Table 1 under "Physical Properties". In Table 1, a "-" for the "H2S Production Amount (mL / g)" result indicates that it was not measured.

[0224] [Table 1]

[0225]

[0226] Based on the above results, the glass of this embodiment becomes glass even when it is composed of crystals through conventional mechanical polishing methods.

[0227] Furthermore, the glass of this embodiment can achieve a high lithium-ion conductivity of over 2 mS / cm while in a glassy state.

[0228] This invention demonstrates that by increasing the content of I, the glass of this embodiment can achieve a higher lithium-ion conductivity.

[0229] Furthermore, it is known that the glass of this embodiment produces low amounts of H2S when exposed to an atmosphere with a dew point of -30°C for 1 hour, and also exhibits high water resistance. For the glasses of Examples 5 and 17, whose water resistance was not evaluated, high homogeneity without residues such as residual sulfur or unreacted raw materials can also be achieved by melting and rapidly cooling the raw material mixture, thus demonstrating similarly high water resistance.

[0230] The various embodiments have been described above, but the present invention is certainly not limited to the examples described above. It is obvious that those skilled in the art will conceive of various modifications or alterations within the scope of the patent claims, and these should be understood to fall within the technical scope of the present invention. Furthermore, the constituent elements of the above embodiments can be combined arbitrarily without departing from the spirit of the invention.

[0231] It should be noted that this application is based on Japanese patent applications filed on September 28, 2023 (Japanese Patent Application No. 2023-168392), September 28, 2023 (Japanese Patent Application No. 2023-168395), and March 29, 2024 (Japanese Patent Application No. 2024-057517), the contents of which are incorporated herein by reference.

Claims

1. A glass comprising Li and P as elements constituting a cationic component, It contains sulfur (S) as an element constituting the anion. The composition, expressed in atomic percent, satisfies: Li: 30-42%, and P：5～16％； The glass transition point is 110–300℃. The lithium-ion conductivity at 25℃ is above 2 mS / cm.

2. The glass according to claim 1, wherein, It further includes at least one element selected from Sn, Sb, Si, Ge, Ga, Al, B, C, Mg, Ca, Sr and Ba as a constituent element of the cation.

3. The glass according to claim 1, wherein, It further includes at least one element selected from F, Cl, Br, I, O, Se, N and C as constituting the anionic component.

4. A crystalline glass comprising a crystalline phase derived from the glass of any one of claims 1 to 3.

5. A sulfide solid electrolyte comprising the crystalline glass of claim 4.

6. An electrode mixture comprising the sulfide solid electrolyte of claim 5.

7. A solid electrolyte layer comprising the sulfide solid electrolyte of claim 5.

8. A lithium-ion secondary battery comprising the sulfide solid electrolyte of claim 5.

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