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

Abstract

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

Description

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

[0001] The present invention relates to glass, crystallized glass, a sulfide solid electrolyte, an electrode mixture, a solid electrolyte layer, and a lithium ion secondary battery.

[0002] Lithium-ion secondary batteries are widely used in portable electronic devices such as mobile phones and laptop computers, as well as in automobiles. Conventionally, liquid electrolytes have been used in lithium-ion secondary batteries, but concerns about leakage and fire have led to the need for larger casings for safety reasons. Furthermore, improvements have been needed to address the short battery life and narrow operating temperature range.

[0003] In response to this, all-solid-state lithium secondary batteries, which use solid electrolytes as the electrolyte for lithium-ion secondary batteries, are attracting attention because they are expected to offer improved safety, high-speed charging and discharging, and smaller cases.

[0004] Solid electrolytes are broadly classified into sulfide solid electrolytes and oxide solid electrolytes. The sulfide ions that make up sulfide solid electrolytes have higher polarizability and exhibit higher ionic conductivity than the oxide ions that make up oxide solid electrolytes.

[0005] On the other hand, sulfide solid electrolytes are highly reactive with water in the air and are prone to generating hydrogen sulfide. Therefore, Patent Document 1 describes a solid electrolyte having excellent water resistance and high ionic conductivity, which is a Li ２ S / P ２ S ５ Sulfide-based glass in which Li / LiI=63 / 21 / 16 or 52 / 17 / 31, ２ S / P ２ S ５ A sulfide-based glass ceramic solid electrolyte is disclosed in which a sulfide-based glass having a composition of Zn / LiBr=64 / 21 / 14 is partially crystallized.

[0006] Japanese Patent Application Publication No. 2018-049834

[0007] The sulfide-based glass described in Patent Document 1 is produced by a mechanical milling method in which raw materials are mechanically reacted using a ball mill or a bead mill.

[0008] However, the inventors' investigations have revealed that glass obtained by mechanical milling tends to contain residues of excess sulfur and unreacted raw materials, which can cause hydrogen sulfide generation. Furthermore, when glass is used in sulfide solid electrolytes, higher lithium ion conductivity is desired.

[0009] Therefore, an object of the present invention is to provide a glass that exhibits high lithium ion conductivity, suppresses hydrogen sulfide generation, and has excellent water resistance. Another object of the present invention is to provide a partially crystallized glass-ceramic useful as a sulfide solid electrolyte. Further objects of the present invention are to provide a sulfide solid electrolyte, an electrode mixture, a sulfide solid electrolyte layer, and a lithium ion secondary battery containing the glass-ceramic.

[0010] After extensive research, the inventors discovered that by employing techniques such as melting and quenching raw materials or raw material mixtures by heating, vitrification is possible even in compositional ranges where vitrification has traditionally been difficult, and that highly homogeneous glass can be obtained without residue. Therefore, the glass exhibits low hydrogen sulfide generation and excellent water resistance. Furthermore, by producing glass, various anion and cation components can be selected, enabling high lithium ion conductivity.

[0011] That is, the present invention relates to the following items [1] to [8]. [1] Glass containing Li and P as elements constituting cationic components and S as an element constituting anionic components, the composition of which, expressed in atomic %, satisfies the following: Li: 30 to 42% and P: 5 to 16%, the glass transition temperature is 110 to 300°C, and the lithium ion conductivity at 25°C is 2 mS / cm or more. [2] The glass according to item [1] above, further containing at least one element selected from the group consisting of Sn, Sb, Si, Ge, Ga, Al, B, C, Mg, Ca, Sr, and Ba as an element constituting the cationic components. [3] The glass according to item [1] or [2] above, further containing at least one element selected from the group consisting of F, Cl, Br, I, O, Se, N, and C as an element constituting the anionic components. [4] Crystallized glass containing a crystalline phase derived from the glass according to any one of items [1] to [3] above. [5] A sulfide solid electrolyte comprising the crystallized glass described in [4]. [6] An electrode mixture comprising the sulfide solid electrolyte described in [5]. [7] A solid electrolyte layer comprising the sulfide solid electrolyte described in [5]. [8] A lithium ion secondary battery comprising the sulfide solid electrolyte described in [5].

[0012] According to the present invention, a glass exhibiting high lithium ion conductivity and excellent water resistance due to suppression of hydrogen sulfide generation can be obtained. Furthermore, by crystallizing at least a portion of this glass, a glass-ceramic useful as a sulfide solid electrolyte can be obtained. Therefore, by using the solid electrolyte containing the glass-ceramic in a solid electrolyte layer, an electrode mixture, or a lithium ion secondary battery, good battery characteristics can be achieved.

[0013] Fig. 1 is a flow diagram showing a method for producing glass according to the present embodiment. Fig. 2 is a flow diagram showing a method for producing crystallized glass according to the present embodiment.

[0014] The present invention will be described in detail below, but the present invention is not limited to the following embodiments and can be modified as desired without departing from the spirit of the present invention. Furthermore, the term "to" indicating a range of values ​​is used to mean that the values ​​before and after it are included as the lower and upper limits.

[0015] <<Glass>> The glass according to this embodiment contains Li and P as elements constituting cationic components, and S as an element constituting anionic components. The composition of the glass satisfies the following, expressed in atomic %, Li: 30 to 42%, and P: 5 to 16%.

[0016] When a conventional mechanical milling method is applied to a raw material mixture obtained by mixing the raw materials so as to satisfy the above composition, the resulting solid is an amorphous phase but does not have a glass transition point. However, in this embodiment, a glass is obtained by melting the raw material mixture and then rapidly cooling it.

[0017] By producing the glass described above, high homogeneity can be achieved, with no residual sulfur or unreacted raw materials, and high water resistance can be achieved by suppressing the generation of hydrogen sulfide. Furthermore, unlike the mechanical milling method, various anion and cation components can be selected to obtain the desired glass without having to worry about the hardness of the raw materials. This also makes it possible to achieve high lithium-ion conductivity.

[0018] The glass according to this embodiment contains Li and P as elements constituting the cationic component, and may further contain at least one element selected from the group consisting of Sn, Sb, Si, Ge, Ga, Al, B, C, Mg, Ca, Sr, and Ba. Among these, 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.

[0019] The elements constituting the cationic component will be described below. The content of each element in the glass is expressed in atomic %.

[0020] Li is an essential element responsible for ion conduction as a solid electrolyte. The Li content in the glass is 30 to 42%, preferably 33 to 41%. From the viewpoint of lithium ion conductivity, the Li content is 30% or more, preferably 33% or more, and more preferably 35% or more. From the viewpoint of vitrification, the Li content is 42% or less, preferably 41% or less, and more preferably 40% or less.

[0021] P is an essential element that forms the glass network. Among sulfides, P-S bonds are highly resistant to both oxidation and reduction. Therefore, as a solid electrolyte, it has a wide potential window and excellent electrochemical stability. The P content in the glass is 5 to 16%, preferably 6 to 14%. Here, from the viewpoint of vitrification, the content is 5% or more, preferably 6% or more, and more preferably 7% or more. Furthermore, from the viewpoint of lithium ion conductivity, the content is 16% or less, preferably 14% or less, and more preferably 12% or less.

[0022] When the glass according to this embodiment contains Si as an element constituting the cationic component, Si has the effect of increasing the viscosity of the melt and promoting vitrification. The Si content in the glass is preferably 0 to 10%, and when Si is contained, it is more preferably 0.5 to 10%, and even more preferably 2 to 9%. Here, from the viewpoint of optimally obtaining the effects of Si, when Si is contained, the content is preferably 0.5% or more, and more preferably 2% or more. Furthermore, from the viewpoint of electrochemical stability, the Si content is preferably 10% or less, and more preferably 9% or less.

[0023] When the glass according to this embodiment contains Sn as an element constituting the cationic component, Sn has the effect of increasing the viscosity of the melt and promoting vitrification. The Sn content in the glass is preferably 0 to 10%, and when Sn is contained, it is more preferably 0.1 to 10%, and even more preferably 0.5 to 8%. Here, from the viewpoint of optimally obtaining the effects of Sn, when Sn is contained, the content is preferably 0.1% or more, and more preferably 0.5% or more. Furthermore, from the viewpoint of electrochemical stability, the Sn content is preferably 10% or less, and more preferably 8% or less.

[0024] When the glass according to this embodiment contains Sb as an element constituting the cationic component, Sb has the effect of increasing the viscosity of the melt and promoting vitrification. The Sb content in the glass is preferably 0 to 10%, and when Sb is contained, it is more preferably 0.1 to 8%, and even more preferably 1 to 5%. Here, from the viewpoint of optimally obtaining the effects of Sb, when Sb is contained, the content is preferably 0.1% or more, and 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.

[0025] When the glass according to this embodiment contains Ge as an element constituting the cationic component, Ge has the effect of promoting an improvement in lithium ion conductivity. The Ge content in the glass is preferably 0 to 10%, and when Ge is contained, it is more preferably 0.1 to 8%, and even more preferably 1 to 5%. Here, from the viewpoint of optimally obtaining the effects of Ge, when Ge is contained, the content is preferably 0.1% or more, and 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.

[0026] When the glass according to this embodiment contains Ga as an element constituting the cationic component, Ga has the effect of promoting an improvement in lithium ion conductivity. The Ga content in the glass is preferably 0 to 10%, and when Ga is contained, it is more preferably 0.1 to 8%, and even more preferably 1 to 5%. Here, from the viewpoint of optimally obtaining the effects of Ga, when Ga is contained, the content is preferably 0.1% or more, and 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.

[0027] When the glass according to this embodiment contains Al as an element constituting the cationic component, Al has the effect of increasing the viscosity of the melt and promoting vitrification. The Al content in the glass is preferably 0 to 10%, and when Al is contained, it is more preferably 0.1 to 8%, and even more preferably 1 to 5%. Here, from the viewpoint of optimally obtaining the effects of Al, when Al is contained, the content is preferably 0.1% or more, and 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.

[0028] When the glass according to this embodiment contains B as an element constituting the cationic component, B has the effect of increasing the viscosity of the melt and promoting vitrification. The content of B in the glass is preferably 0 to 10%, and when B is contained, it is more preferably 0.1 to 8%, and even more preferably 1 to 5%. Here, from the viewpoint of optimally obtaining the effects of B, when B is contained, the content is preferably 0.1% or more, and 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.

[0029] When the glass according to this embodiment contains C as an element constituting the cationic component, C has the effect of enhancing glass-forming ability. The C content in the glass is preferably 0 to 10%, and when C is contained, it is more preferably 0.1 to 8%, and even more preferably 1 to 5%. Here, from the viewpoint of optimally obtaining the effects of C, when C is contained, the content is preferably 0.1% or more, and 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.

[0030] When the glass according to this embodiment contains alkaline earth metal elements as elements constituting the cation components, the alkaline earth metal elements have the effect of improving glass-forming ability. Examples of alkaline earth metal elements include one or more elements selected from the group consisting of Mg, Ca, Sr, and Ba. The content of each alkaline earth metal element in the glass is preferably 0 to 10%, and when alkaline earth metal elements are included, the content is more preferably 0.1 to 8%, and even more preferably 1 to 5%. Here, from the viewpoint of optimally obtaining the effects of the alkaline earth metal elements, when alkaline earth metal elements are included, the content is preferably 0.1% or more, and even 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. Furthermore, the total content of alkaline earth metal elements in the glass is preferably 0 to 20%, and when alkaline earth metal elements are included, the content is more preferably 0.2 to 18%, and even more preferably 1 to 15%. Here, the total content is preferably 0.2% or more, more preferably 1% or more, and is preferably 20% or less, more preferably 18% or less, and even more preferably 15% or less.

[0031] The glass according to this embodiment contains S as an element constituting an anion component, but may further contain at least one element selected from the group consisting of F, Cl, Br, I, O, Se, N, and C. Among these, from the viewpoint of improving ionic conductivity, it preferably contains at least one element selected from the group consisting of F, Cl, Br, and I, more preferably contains at least one element selected from the group consisting of Cl, Br, and I, and even more preferably contains I. Furthermore, from the viewpoint of improving vitrification ability, it preferably contains at least one element selected from the group consisting of O, Se, N, and C.

[0032] The elements constituting the anion component will be described below. The content of each element in the glass is expressed in atomic %.

[0033] S is an element that forms P-S bonds together with P and is an essential element for forming a glass phase. The content of S in the glass is preferably 30 to 60%, more preferably 33 to 55%, and even more preferably 37 to 50%. From the viewpoint of vitrification, the 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 content is preferably 60% or less, more preferably 55% or less, and even more preferably 50% or less.

[0034] When the glass according to this embodiment contains a halogen element (X) as an element constituting an anion component, X is an element that contributes to high lithium ion conductivity. The total content of X in the glass is preferably 0 to 20%. When X is included, it is more preferably 1 to 20%, more preferably 1 to 12%, or even 2 to 10%. Here, from the viewpoint of optimally obtaining the effects of X, when X is included, the total content is preferably 1% or more, more preferably 2% or more, even more preferably 3% or more, and particularly preferably 6% or more. Furthermore, from the viewpoint of preventing precipitation of lithium halide crystals, the total content of X is preferably 20% or less, more preferably 19% or less, and even more preferably 17% or less. It has been considered that vitrification is particularly difficult in a composition range with a high X content using the conventional mechanical milling method. However, the inventors' investigations have newly discovered that vitrification is possible even in this composition range and high lithium ion conductivity can be achieved by employing techniques such as melting by heating and rapid cooling of raw materials or raw material mixtures obtained by mixing them. Therefore, vitrification is possible even with a composition having a total content of about 20% of X. However, in the glass according to this embodiment, when lithium halide crystals are likely to precipitate, the total content of X may be 12% or less, or even 10% or less.

[0035] In particular, the total content of Br and I preferably accounts for 50% or more, more preferably 70% or more, and may even be 100%, i.e., consist of only Br and I, of the total content of X. Furthermore, the content ratio represented by 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, this does not in any way exclude the inclusion of only Cl as X.

[0036] When the glass according to this embodiment contains F as an element constituting an anion component, the F content in the glass is preferably 0.1 to 20%, may be 0.1 to 10%, or may be 0.5 to 5%. Here, the F content is preferably 0.1% or more, more preferably 0.5% or more, even more preferably 3% or more, and particularly preferably 6% or more. Furthermore, the F content is preferably 20% or less, more preferably 19% or less, and even more preferably 17% or less. When lithium fluoride crystals are likely to precipitate, the F content may be 10% or less, or may be 5% or less.

[0037] When the glass according to this embodiment contains Cl as an element constituting an anion component, the Cl content in the glass is preferably 0.1 to 20%, may be 0.1 to 10%, or may be 0.5 to 5%. Here, the Cl content is preferably 0.1% or more, more preferably 0.5% or more, even more 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 even more preferably 17% or less. When lithium chloride crystals are likely to precipitate, the Cl content may be 10% or less, or may be 5% or less.

[0038] When the glass according to this embodiment contains Br as an element constituting an anion component, the Br content in the glass is preferably 0.1 to 20%, alternatively 0.1 to 10%, or alternatively 1 to 8%. Here, the Br content is preferably 0.1% or more, more preferably 1% or more, even more 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 even more preferably 17% or less. When lithium bromide crystals are likely to precipitate, the Br content may be 10% or less, or alternatively 8% or less.

[0039] When the glass according to this embodiment contains I as an element constituting an anion component, I is preferred because I particularly contributes to improving ionic conductivity. The I content in the glass is preferably 0.1 to 20%, may be 0.1 to 10%, may be 1 to 8%, or may be 2 to 6%. Here, the I content is preferably 0.1% or more, more preferably 1% or more, even more preferably 2% or more, even more preferably 3% or more, and particularly preferably 6% or more. Furthermore, the 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 are likely to precipitate or from the viewpoint of improving vitrification, the I content may be 10% or less, may be 8% or less, or may be 6% or less.

[0040] When the glass according to this embodiment contains O as an element constituting an anion component, O has the effect of improving ionic conductivity. The O content in the glass is preferably 0 to 5%, and when O is contained, it is more preferably 0.1 to 4%, and even more preferably 0.5 to 3%. Here, from the viewpoint of optimally obtaining the effects of O, when O is contained, the content is preferably 0.1% or more, and more preferably 0.5% or more. Furthermore, from the viewpoint of water resistance, the O content is preferably 5% or less, more preferably 4% or less, and even more preferably 3% or less.

[0041] When the glass according to this embodiment contains Se as an element constituting an anion component, Se has the effect of improving ionic conductivity. The Se content in the glass is preferably 0 to 5%, and when Se is included, it is more preferably 0.1 to 4%, and even more preferably 0.5 to 3%. Here, from the viewpoint of optimally obtaining the effects of Se, when Se is included, the content is preferably 0.1% or more, and 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.

[0042] When the glass according to this embodiment contains N as an element constituting an anion component, N has the effect of improving ionic conductivity. The N content in the glass is preferably 0 to 5%, and when N is contained, it is more preferably 0.1 to 4%, and even more preferably 0.5 to 3%. Here, from the viewpoint of optimally obtaining the effects of N, when N is contained, the content is preferably 0.1% or more, and 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.

[0043] When the glass according to this embodiment contains C as an element constituting an anionic component, C has the effect of improving ionic conductivity. The C content in the glass is preferably 0 to 5%, and when C is contained, it is more preferably 0.1 to 4%, and even more preferably 0.5 to 3%. Here, from the viewpoint of optimally obtaining the effects of C, when C is contained, the content is preferably 0.1% or more, and 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. Note that C may be an element constituting a cationic component or an element constituting an anionic component. When sulfur (S) is in excess relative to the glass, C can be determined to be an element constituting a cationic component, and when sulfur is deficient, C can be determined to be an element constituting an anionic component.

[0044] The glass according to this embodiment may contain other elements in addition to the elements constituting the cation component or anion component, such as Na, K, Y, Zr, Cr, Zn, Fe, Co, Ti, and Mn, within the scope of the present invention.

[0045] The total content of the other elements in the glass according to this embodiment may be, for example, 0 to 5% in atomic %, or may be 0.1 to 4% or 0.5 to 3% when other elements are included. Here, the total content may be 0.1% or more, 0.5%, or 4% or less, or 3% or less.

[0046] The composition of the glass according to this embodiment, expressed in atomic %, may be 30-42% Li and 5-16% P. In addition, it is preferable that one or more of the following be satisfied: 30-60% S, 1-20% X, 1-10% Si, and 0.1-10% Sn. It is also preferable that two or more, and even more preferable that three or more are satisfied. Furthermore, when the above X: 1-20% is satisfied, it is more preferable that at least one of 0.1-19% Br and 0.1-19% I is satisfied. The composition of the glass according to this embodiment may be one or more of the following: 30-60% S, 1-12% X, 1-10% Si, and 0.1-10% Sn. It may also be two or more, or even three or more. Furthermore, when the above X: 1-12% is satisfied, it may also be one or more of 0.1-10% Br and 0.1-10% I.

[0047] The constituent elements of the glass according to this embodiment and the methods for determining their respective contents (composition ratios) vary depending on the element. For example, P, S, Sn, Sb, Si, Ge, Ga, Al, Mg, Ca, Sr, Ba, and Se can be determined by ICP atomic emission spectroscopy, Li and B by atomic absorption spectroscopy, X by ion chromatography, and C, O, and N by XPS (X-ray photoelectron spectroscopy). Details of each analysis will be described later in the Examples section.

[0048] The glass according to this embodiment has a glass transition point of 110 to 300°C, preferably 130 to 300°C, more preferably 140 to 290°C, and particularly preferably 150 to 280°C. In this embodiment, a glass having a glass transition point can be obtained by melting a raw material mixture and rapidly cooling it. From the viewpoint of formability, which improves the stability of the 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. The glass transition point in this specification is the temperature at the first inflection point in a DSC chart obtained by differential scanning calorimetry (DSC), and can be adjusted by the glass composition and the cooling rate from the melt.

[0049] The crystallization temperature of the glass according to this embodiment is not particularly limited, but is preferably 130 to 400° C., more preferably 140 to 400° C., and particularly preferably 150 to 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. From the viewpoint of glass stability, the crystallization temperature is preferably 400° C. or lower, and more preferably 370° C. or lower.

[0050] When the glass transition temperature of the glass according to this embodiment is Tg and the crystallization temperature is Tc, the temperature difference represented by (Tc-Tg) is preferably 10 to 200°C, more preferably 20 to 180°C. From the viewpoint of glass stability, the difference is preferably 10°C or more, more preferably 20°C or more. Furthermore, from the viewpoint of productivity, the difference is preferably 200°C or less, more preferably 180°C or less.

[0051] When the glass according to this embodiment is compressed at 380 MPa, the lithium ion conductivity at 25°C is 2 mS / cm or more, preferably 3 mS / cm or more, and the higher the better. The lithium ion conductivity in this specification is determined by AC impedance measurement using a measurement sample obtained by compressing a powder sample at 380 MPa. Specifically, the AC impedance of the measurement 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, and the value obtained from the resulting Nyquist plot is taken as the lithium ion conductivity.

[0052] The lithium ion conductivity can be adjusted by the glass composition, reducing thermal unevenness during quenching of the molten raw material mixture, and adjusting the cooling rate. In particular, the glass according to this embodiment is obtained by melting and quenching the raw material mixture, rather than by conventional mechanical milling. This broadens the range that can be vitrified, making it easier to incorporate multiple desired anion and cation components. As a result, it becomes possible to adopt a composition that can achieve high lithium ion conductivity.

[0053] The glass according to this embodiment was exposed to the atmosphere at a dew point of −30° C. for 1 hour. ２ The amount of sulfur generated is preferably 10 mL / g or less, more preferably 4 mL / g or less, even more preferably 1 mL / g or less, and particularly preferably 0.1 mL / g or less, and the smaller the amount the better. ２ More specific conditions for measuring the amount of sulfur generated are as follows: First, a sample is passed through a 100 μm mesh to obtain powder with an average particle size of 10 to 20 μm. Then, 10 mg of this powder is exposed to the atmosphere with a humidity controlled to a dew point of -30°C for 1 hour, and the amount of hydrogen sulfide (H ２ S) Monitor the amount of generation and calculate the total amount as H ２ This is the amount of S generated.

[0054] <<Crystalline Glass>> The crystallized glass according to this embodiment is obtained by heat-treating the glass described in the above <<Glass>> to crystallize at least a portion of it. That is, the crystallized glass according to this embodiment contains a crystalline phase derived from the glass described in the above <<Glass>>. Optionally, the crystallized glass may further contain an amorphous phase, and in this case, the amorphous phase contains a phase consisting of the glass described in the above <<Glass>>.

[0055] Here, the phase derived from the glass means a crystalline phase obtained by crystallizing the glass by heat treatment. Except for the case where the crystallized glass is composed only of a crystalline phase with a crystallinity of 100%, the glass from which the crystalline phase originates can be estimated from the crystal structure and mass ratio of the crystalline phase and the composition of the entire crystallized glass.

[0056] Specifically, the XRD pattern obtained by powder X-ray diffraction (XRD) measurement of crystalline phase is subjected to Rietveld analysis etc., to calculate the crystalline structure and mass ratio of crystalline phase.On the other hand, the composition of the whole crystallized glass is similar to the method of determining the constituent elements of glass and their respective contents (composition ratio) as described above, and according to the type of element, can be determined by ICP emission spectroscopy, atomic absorption spectroscopy analysis, ion chromatography analysis, XPS analysis etc.Then, by subtracting the composition of crystalline phase by its mass ratio from the composition of the whole crystallized glass, the composition and amount of amorphous phase can be calculated.The composition of this amorphous phase is regarded as the glass composition before crystallization, and if it corresponds to the glass according to the present embodiment described in above "Glass", this crystallized glass can be judged to correspond to the crystallized glass according to the present embodiment.

[0057] The glass composition before crystallization to obtain crystallized glass is called the matrix composition, and the matrix composition of the crystallized glass according to this embodiment is the same as the composition described in the above "Glass". That is, the composition of the amorphous phase of the crystallized glass according to this embodiment can be said to be the same as the matrix composition.

[0058] Furthermore, the composition of the crystalline phase in this embodiment differs from the above-mentioned base composition by at most about 30%, and there is a tendency for P to decrease. The above-mentioned crystalline phase can have a thiosilicon region II type or LGPS type crystal structure.

[0059] If the crystallized glass according to this embodiment exhibits a lithium ion conductivity higher than the known lithium ion conductivity when the crystal structure of the crystal phase is adopted, it can be assumed that the glass is a crystallized product of the above-mentioned "glass" obtained by melting and rapidly cooling the raw material mixture, rather than by the conventional mechanical milling method.

[0060] The proportion of the crystalline phase (crystallinity) in the crystallized glass according to 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. From the viewpoint of lithium ion conductivity, the crystallinity is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more. From the viewpoint of productivity, the crystallinity is preferably 100% by mass or less, more preferably 90% by mass or less, and even more preferably 80% by mass or less. The crystallized glass according to this embodiment may have a crystallinity of 100% by mass and consist solely of a crystalline phase. The crystallinity is determined by powdering the crystallized glass, performing powder X-ray diffraction (XRD) measurement together with a crystal powder serving as an internal standard, determining the proportion of crystals, and then subtracting this from 100% by mass to perform Rietveld analysis.

[0061] Since the glass before crystallization in this embodiment has high lithium ion conductivity, the lithium ion conductivity of the crystallized glass according to this embodiment is also high, and it is suitable for use as a solid electrolyte. That is, when the crystallized glass according to this embodiment is compressed under 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.

[0062] <Sulfide Solid Electrolyte> The sulfide solid electrolyte according to this embodiment includes the crystallized glass described above in <<Crystalline Glass>>. The constituent elements and composition ratios of the crystallized glass are considered to be substantially the same as the constituent elements and composition ratios of the sulfide solid electrolyte according to this embodiment. Therefore, preferred aspects of the constituent elements and composition ratios of the sulfide solid electrolyte can be interpreted as preferred aspects of the constituent elements and composition ratios of the crystallized glass. However, the sulfide solid electrolyte according to this embodiment may also include phases other than the crystallized glass.

[0063] The average particle size (D50) of the sulfide solid electrolyte according to this embodiment is preferably 0.5 to 100 μm, more preferably 0.8 to 80 μm, and even more preferably 1 to 50 μm. From the viewpoint of reducing the load of the pulverization process when using the sulfide solid electrolyte in a secondary battery, the 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 handling, the 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. The average particle size (D50) can be adjusted by subjecting the obtained sulfide solid electrolyte to coarse pulverization. Conventional methods for coarse pulverization can be used, including, for example, a cutter mill, a planetary ball mill, a bead mill, and a jet mill. Wet pulverization is preferred when performing coarse pulverization.

[0064] The sulfide solid electrolyte according to this embodiment is suitable as an electrolyte for a lithium ion secondary battery. When used in a lithium ion secondary battery, the sulfide solid electrolyte forms a solid electrolyte layer together with other components such as a binder, as necessary. That is, the solid electrolyte layer according to this embodiment contains the sulfide solid electrolyte. Conventionally known binders and other components constituting the solid electrolyte layer can be used.

[0065] The content of the sulfide solid electrolyte according to this embodiment is preferably 80 mass % or more, and more preferably 90 mass % or more, relative to the entire solid electrolyte layer.

[0066] The sulfide solid electrolyte according to this embodiment may be mixed with a positive electrode active material or a negative electrode active material and used as an electrode mixture for a positive electrode layer or a negative electrode layer. That is, the electrode mixture according to this embodiment contains the sulfide solid electrolyte. 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 may be conventionally known materials.

[0067] The lithium ion secondary battery according to this embodiment includes a positive electrode layer, a solid electrolyte layer, and a negative electrode layer, and it is preferable that at least one layer selected from the group consisting of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer contains the sulfide solid electrolyte according to this embodiment. That is, the lithium ion secondary battery according to this embodiment includes the sulfide solid electrolyte.

[0068] The lithium ion secondary battery may have any of a variety of shapes, including a coin shape, a sheet shape (film shape), a folded shape, a wound bottomed cylindrical shape, and a button shape, and may be appropriately selected depending on the intended use.

[0069] <<Method for Producing Glass and Crystallized Glass>> The method for producing glass according to this embodiment includes the following steps 1 and 2 in order as steps S1 and S2, as shown in Fig. 1. Step S1: Step 1: Heating a raw material mixture containing raw materials containing Li, P, and S to obtain a melt. Step S2: Step 2: Cooling and solidifying the melt obtained in step 1 to obtain glass.

[0070] The method for producing crystallized glass according to this embodiment includes the following steps 1 to 3 in order, as steps S1 to S3, as shown in Figure 2. Steps S1 and S2 are the same as steps S1 and S2 in the method for producing glass according to this embodiment. Step S1: Step 1, in which a raw material mixture containing Li, P, and S is heated to obtain a melt. Step S2: Step 2, in which the melt obtained in step 1 is cooled and solidified to obtain glass. Step S3: Step 3, in which the glass obtained in step 2 is heat-treated and a portion of it is crystallized to obtain crystallized glass.

[0071] The heating in step 1 and the cooling in step 2 are carried out under atmospheric pressure conditions, and the cooling rate during cooling and solidification is 100°C / sec or more. During cooling, the molten material is cooled evenly and is cooled to prevent uneven heating. This eliminates residues such as residual sulfur and unreacted raw materials, resulting in a homogeneous material and achieving good water resistance. Furthermore, the wide range in which vitrification can occur and the increased freedom in composition allow for high lithium ion conductivity. Note that, in this specification, "under atmospheric pressure conditions" refers to a pressure range of approximately (gauge pressure ±15 kPa).

[0072] In the above step 1, the raw materials are mixed so that the resulting glass contains Li and P as elements constituting the cation component and S as an element constituting the anion component, and the composition satisfies, in atomic %, Li: 30 to 42% and P: 5 to 16%.

[0073] Each step will be explained below.

[0074] <Step 1> Step S1 in this embodiment is step 1 in which raw materials are mixed to obtain a raw material mixture containing Li, P, and S, and the obtained mixture is heated. 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, when 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 material containing Li, the raw material containing P, and the raw material containing S, to obtain a raw material mixture containing Li, P, S, and X. Here, the X element is at least one element selected from the group consisting of F, Cl, Br, and I.

[0075] Examples of raw materials containing Li include lithium sulfide (Li ２ S), lithium carbonate (Li ２ CO ３ ), lithium sulfate (Li ２ SO ４ ), lithium oxide (Li ２ Examples of the raw material containing Li include lithium compounds such as lithium ion (LiO), lithium hydroxide (LiOH), and metallic lithium. One type of raw material containing Li may be used, or two or more types may be used in combination.

[0076] From the viewpoint of obtaining a sulfide-based glass, it is preferable to use lithium sulfide as the raw material containing Li element. Furthermore, when the glass to be obtained contains a halogen element, lithium halide (LiX, where X is a halogen element) is also preferable as the raw material containing Li element. Lithium halide will be described later.

[0077] As a raw material containing P element, for example, diphosphorus pentasulfide (P ２ S ５ ), diphosphorus trisulfide (P ２ S ３ ) and other phosphorus sulfides, sodium phosphate (Na ３ P.O. ４ The raw material containing P may be used alone or in combination of two or more.

[0078] The raw material containing the P element is preferably phosphorus sulfide, and more preferably diphosphorus pentasulfide (P ２ S ５ When the above-mentioned elemental phosphorus is used as the raw material containing the P element, examples thereof include yellow phosphorus, red phosphorus, purple phosphorus, and black phosphorus.

[0079] Examples of raw materials containing S element include lithium sulfide (Li ２ S), diphosphorus trisulfide (P ２ S ３ ), diphosphorus pentasulfide (P ２ S ５ ), other sulfur compounds containing phosphorus, and compounds containing sulfur. ２ S, CS ２ , iron sulfide (FeS, Fe ２ S ３ , FeS ２ , Fe １－ｘ S, etc.), bismuth sulfide (Bi ２ S ３ ), copper sulfide (CuS, Cu ２ S, Cu １－ｘ The raw material containing the S element may be used alone or in combination of two or more.

[0080] The raw material containing the S element is preferably lithium sulfide or phosphorus sulfide from the viewpoint of preventing the inclusion of elements other than those constituting the target glass. As the phosphorus sulfide, diphosphorus pentasulfide (P ２ S ５ Lithium sulfide is a compound that serves as both a raw material containing Li and a raw material containing S, and phosphorus sulfide is a compound that serves as both a raw material containing S and a raw material containing P.

[0081] Examples of raw materials containing an X element include lithium halides such as lithium fluoride (LiF), lithium chloride (LiCl), lithium bromide (LiBr), and lithium iodide (LiI), phosphorus halides, phosphoryl halides, sulfur halides, sodium halides, and boron halides. One type of raw material containing an X element may be used, or two or more types may be used in combination.

[0082] From the viewpoint of reactivity, the raw material containing the X element is preferably a lithium halide, more preferably LiCl, LiBr, or LiI, and even more preferably LiBr or LiI.

[0083] Other raw materials may be further mixed to obtain a raw material mixture according to the desired glass composition. For example, when the glass further contains at least one element selected from the group consisting of Sn, Sb, Si, Ge, Ga, Al, B, C, Mg, Ca, Sr, and Ba as an element constituting a cationic component, a raw material containing the element may be further used. The raw material is not limited to a compound, and may be a simple metal.

[0084] When the glass further contains, as an element constituting an anion component, at least one element selected from the group consisting of O, Se, N, and C in addition to the above-mentioned X, a raw material containing such an element may be further used. The raw material is not limited to a compound, and may be a simple metal.

[0085] When the glass further contains other elements as described above, raw materials containing Na, K, Y, Zr, Cr, Zn, Fe, Co, Ti, Mn, etc. may also be used. Note that Si, B, Ge, Al, Sn, and Sb are elements that can occupy the position of P when the obtained glass is further made into crystallized glass.

[0086] These other raw materials can be conventionally known. For example, the raw material containing Si element is Si, SiO ２ , SiS ２ Among them, from the viewpoint of lithium ion conductivity, SiO ２ These compounds may be used alone or in combination of two or more. The raw material containing Sn element is Sn, SnS, SnS ２ , SnO, SnO ２ , SnCl ２ Among them, from the viewpoint of lithium ion conductivity, SnS ２ , SnCl ２ is preferred, and SnS ２ These compounds may be used alone or in combination of two or more. Examples of raw materials containing Sb include Sb, Sb ２ S ３ , Sb ２ O ３ , Sb ２ O ５ , SbCl ３ , SbCl ５ Among them, from the viewpoint of lithium ion conductivity and water resistance, Sb ２ S ３ , SbCl ３ is preferred, and Sb ２ S ３ These compounds may be used alone or in combination of two or more. The raw material containing Ge element is Ge, GeO ２ , GeS, GeS ２ , GeCl ２ Among them, from the viewpoint of lithium ion conductivity, GeS ２ , GeCl ２ is preferred, and GeS ２ These compounds may be used alone or in combination of two or more. Examples of raw materials containing Al element include Al, Al ２ S ３ , Al ２ O ３ , AlCl ３Among them, Al is the most suitable from the viewpoint of lithium ion conductivity and water resistance. ２ S ３ , AlCl ３ is preferred, and Al ２ S ３ These compounds may be used alone or in combination of two or more. Examples of raw materials containing B element include B, B ２ O ３ , B ２ S ３ Among them, from the viewpoint of water resistance of glass, B ２ O ３ These compounds may be used alone or in combination of two or more.

[0087] These raw materials are blended appropriately according to the composition of the glass to be obtained. Specifically, to obtain the glass and crystallized glass described in the above "Glass" and "Crystalline Glass," the raw materials are mixed so as to contain Li, P, and S and to satisfy at least the following ratios: Li: 30 to 42% and P: 5 to 16%. In addition to the above, preferred embodiments of the resulting glass and crystallized glass are the same as those described in the above "Glass" and "Crystalline Glass," respectively.

[0088] It is preferable that each raw material has a small particle size in order to shorten the holding time during heating to obtain a melt. Furthermore, if the particle size of the raw materials is too large, it may affect the homogeneity of the glass, so from this perspective, it is preferable that the particle size of the raw materials is relatively small. However, the manufacturing method according to this embodiment has excellent composition controllability. Therefore, even if raw materials with particle sizes that may reduce homogeneity in conventional manufacturing methods are used, the manufacturing method according to this embodiment can produce more homogeneous glass.

[0089] From the above viewpoint, specifically, the particle size of each raw material is preferably 1 mm or less, more preferably 500 μm or less, even more preferably 250 μm or less, even more preferably 100 μm or less, and particularly preferably 50 μm or less. Smaller particle sizes are preferable, but a practical lower limit is about 0.1 μm, and the particle size may be 1 μm or more, or even 5 μm or more. Furthermore, as described above, according to the manufacturing method of this embodiment, homogeneous glass can be easily obtained even when raw materials with relatively large particle sizes are used. Taking this into consideration, for example, from the viewpoint of reducing manufacturing costs, the particle size of each raw material may be 10 μm or more, 100 μm or more, or 250 μm or more.

[0090] From 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 production costs, 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. In this specification, the particle size of each raw material refers to the average particle size (D50) expressed as the median diameter obtained from a volume-based particle size distribution chart obtained by measuring the particle size distribution using a laser diffraction particle size distribution analyzer MT3300EXII manufactured by Microtrac.

[0091] The raw materials can be mixed, for example, in a mortar, mixed using a media such as a planetary ball mill, or mixed without media such as a pin mill, a powder mixer, or airflow mixing. The raw materials may be made amorphous by mixing before heating.

[0092] The specific method for heating the raw material mixture to obtain a melt is not particularly limited, except that the heating is performed under atmospheric pressure. In the production method according to this embodiment, the heating to melt the raw material mixture is performed under atmospheric pressure, thereby reducing the compositional difference between the composition of the raw material mixture and the composition of the resulting glass. Furthermore, by performing the heating under a gas atmosphere containing the S element, the compositional difference can be further suppressed. Note that in the production method according to this embodiment, the heating to obtain a melt is performed in an atmosphere-controlled environment under atmospheric pressure, and does not need to be performed in a sealed tube. However, this does not in any way exclude the use of a sealed tube.

[0093] Here, the difference between a sealed tube and an environment in which the atmosphere is controlled under normal pressure conditions is that in the sealed tube, the pressure inside the container is a vacuum, i.e., less than (gauge pressure -15 kPa), whereas in the environment in which the atmosphere is controlled under normal pressure conditions, the pressure inside the container during heating is within the range of (gauge pressure ±15 kPa).

[0094] That is, in the production method according to this embodiment, heating to obtain a melt is carried out under normal pressure conditions (gauge pressure ±15 kPa).

[0095] The pressure during the heating may be under normal pressure conditions of (gauge pressure ±15 kPa), preferably (gauge pressure ±10 kPa), more preferably (gauge pressure ±5 kPa), and even more preferably (gauge pressure ±2 kPa).

[0096] When the raw material mixture is heated, it is preferable to adjust the proportions of Li and P added in the raw material mixture so as to achieve the desired content ratios of Li and P in the glass, taking into account that Li is a volatile element and P is a volatile element, for example. The production method according to this embodiment may be a batch method or a continuous method.

[0097] Examples of heat-resistant containers for containing the raw material mixture include heat-resistant containers made of carbon, heat-resistant containers containing oxides such as quartz, quartz glass, borosilicate glass, aluminosilicate glass, alumina, zirconia, and mullite, heat-resistant containers containing nitrides such as silicon nitride and boron nitride, and heat-resistant containers containing carbides such as silicon carbide. These heat-resistant containers may be formed in bulk from the above-mentioned materials, or may be containers on which a layer of carbon, oxide, nitride, carbide, or the like is formed, such as a carbon-coated quartz tube.

[0098] The heating temperature when obtaining a melt of the raw material mixture varies depending on the raw materials used and the composition of the raw material mixture, but is, for example, preferably 600 to 950°C, more preferably 630 to 850°C, and even more preferably 650 to 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. Furthermore, from the viewpoint of suppressing composition deviation due to volatilization of components, the heating temperature is preferably 950°C or lower, more preferably 850°C or lower, and even more preferably 750°C or lower.

[0099] The heating time varies depending on the scale, but is preferably 10 minutes to 10 hours, more preferably 30 minutes to 9.5 hours, even more preferably 45 minutes to 9 hours, and particularly preferably 1 to 9 hours. From the viewpoint of smoothly progressing the 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. 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.

[0100] The atmosphere in the container during heating is not particularly limited. For example, it may be a nitrogen atmosphere, an argon atmosphere, or a gas atmosphere containing an S element. Among these, a gas atmosphere containing an S element is preferred from the viewpoint of more suitably suppressing composition deviation.

[0101] When the gas atmosphere contains S element, examples of the S element source include sulfur gas, hydrogen sulfide gas, sulfur dioxide gas, etc., and sulfur gas is preferred from the viewpoint of reactivity with the raw material mixture. Alternatively, the gas containing S element may be introduced by adding elemental sulfur powder and vaporizing the elemental sulfur powder by heating. The elemental sulfur powder may be added together with the raw materials when mixing the raw materials to obtain the raw material mixture, or may be added separately after the raw material mixture is obtained. 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 elemental sulfur powder. The gas containing S element may be introduced by adding the above-mentioned sulfur gas, hydrogen sulfide gas, sulfur dioxide gas, etc., and the gas containing S element resulting from the addition of elemental sulfur powder.

[0102] The gas containing the S element is preferably used as a mixed gas with, for example, an inert gas, such as the S element source gas. The mixing ratio with the inert gas is arbitrary and is not particularly limited as long as the cumulative amount of S element introduced relative to the mass of the raw material mixture can be set to a desired value.

[0103] Examples of the inert gas include nitrogen gas, argon gas, and helium gas, and these may be used alone or in combination of two or more.

[0104] The dew point during heating is preferably −20° C. or lower, and although there is no particular lower limit, it is usually about −80° C. The oxygen concentration is preferably 1000 ppm by volume or lower.

[0105] In step 1, whether the molten mixture of raw materials is dissolved can be confirmed by the absence of peaks derived from crystals in high-temperature X-ray diffraction measurement. It can also be confirmed by heating the molten mixture at a predetermined temperature and checking for fluidity by tilting the molten mixture.

[0106] <Step 2> Step S2 in this embodiment is step 2 in which the melt obtained in step 1 is cooled and solidified to obtain glass.

[0107] Cooling and solidification are carried out under atmospheric pressure conditions. As mentioned above, atmospheric pressure conditions refer to an atmosphere under a pressure of approximately (gauge pressure ±15 kPa). The pressure during cooling and solidification may be atmospheric pressure conditions of (gauge pressure ±15 kPa), preferably (gauge pressure ±10 kPa), more preferably (gauge pressure ±5 kPa), and even more preferably (gauge pressure ±2 kPa).

[0108] The cooling rate during cooling and solidification is 100°C / sec or more, preferably 100 to 100,000°C / sec, more preferably 200 to 50,000°C / sec, and even more preferably 300 to 10,000°C / sec. Here, it has been discovered that by using an ultra-rapid cooling rate of 100°C / sec or more, which is faster than conventional rates, even compositions that would previously have precipitated into crystals can be solidified as glass. This significantly increases the degree of freedom in the composition, allowing the selection of compositions that exhibit high lithium ion conductivity.

[0109] Furthermore, by performing the cooling and solidification process so that the melt is cooled evenly and there is no uneven heating, a higher lithium ion conductivity can be achieved compared to conventional glasses. As a result, the lithium ion conductivity of the glass-ceramics obtained by heat-treating the glass can also be increased. Furthermore, by performing the cooling and solidification process under normal pressure conditions, the compositional difference between the composition of the raw material mixture and the composition of the resulting glass can be reduced.

[0110] The cooling rate is 100°C / sec or more, but from the viewpoint of ease of glass formation, it is preferably 200°C / sec or more, more preferably 300°C / sec or more. The upper limit of the cooling rate is not particularly limited, but from the viewpoint of equipment capacity, it is preferably 100,000°C / sec or less, more preferably 50,000°C / sec or less, and even more preferably 10,000°C / sec or less. The above-mentioned ultra-rapid cooling can be achieved, for example, by using a rapid-cooling twin roll.

[0111] The glass obtained as described above may be used as a sulfide solid electrolyte as it is without being crystallized in step 3. The sulfide solid electrolyte may also be used as a sulfide solid electrolyte layer, an electrode mixture, or a lithium ion secondary battery. The glass may be crushed, dried, or the like depending on the intended use.

[0112] <Step 3> In this embodiment, step S3 is step 3 in which the glass obtained above is heat-treated to crystallize at least a portion of it to obtain crystallized glass. The crystallized glass thus obtained may be used as a sulfide solid electrolyte, and may also be used in a sulfide solid electrolyte layer, an electrode mixture, or a lithium-ion secondary battery. Furthermore, the crystallized glass may be crushed, dried, or the like depending on the intended use.

[0113] The temperature in the heat treatment can be determined depending on the crystallization temperature of the glass. Specifically, from the viewpoint of effectively promoting crystallization, the temperature in the heat treatment is preferably (crystallization temperature - 15°C) or higher, may be (crystallization temperature - 10°C) or higher, may be a temperature higher than the crystallization temperature, or may be (crystallization temperature + 1°C) or higher. Furthermore, from the viewpoint of preventing the precipitation of crystals other than the desired crystalline phase when heated at a high temperature, the crystallization temperature is preferably, for example, (crystallization temperature + 20°C) or lower, and more preferably (crystallization temperature + 15°C) or lower.

[0114] The crystallization temperature in this specification means the temperature at the top of the exothermic peak observed when the glass obtained in step 2 is subjected to differential scanning calorimetry (DSC) and heated at a heating rate of 10°C / min.

[0115] 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, even more preferably 5 minutes to 2 hours, and even more preferably 10 minutes to 100 minutes. Here, from the viewpoint of quality stability, the 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 heating time is preferably 6 hours or less, more preferably 3 hours or less, even more preferably 2 hours or less, and even more preferably 100 minutes or less. By adjusting the heating temperature and heating time during crystallization, the content ratio of the crystalline phase in the crystallized glass can be adjusted.

[0116] The heating atmosphere during crystallization may be a vacuum atmosphere, a nitrogen atmosphere, an argon atmosphere, a dry air atmosphere, etc. Among these, a nitrogen atmosphere or an argon atmosphere is preferred from the viewpoint of not impairing the lithium ion conductivity.

[0117] The dew point during crystallization is preferably −30° C. or lower. The oxygen concentration during crystallization may be a dry air environment, but from the viewpoint of safety, it is preferably 5% by volume or lower.

[0118] After heating, the glass is cooled to room temperature at a rate of, for example, 1 to 10,000° C. / min, thereby obtaining the crystallized glass according to this embodiment.

[0119] The crystallized glass obtained above can be suitably used as a sulfide solid electrolyte. The sulfide solid electrolyte may also be used as a sulfide solid electrolyte layer, an electrode mixture, or a lithium-ion secondary battery. The crystallized glass may be crushed, dried, or otherwise processed depending on the intended use.

[0120] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these. Examples 1 to 5 and 9 to 17 are working examples, Examples 6 to 8 are comparative examples, and Example 18 is a reference example.

[0121] Test Examples Examples 1 to 17 Lithium sulfide powder (manufactured by Albemarle, purity 99.9%), diphosphorus pentasulfide powder (manufactured by Perimeter, purity 95 to 100%), and optionally SiS were mixed in a dry nitrogen gas atmosphere to obtain the composition ratios shown in Table 1. ２ Powder (Mitsuwa Chemical Co., Ltd., purity 99%), SnS ２A raw material mixture was obtained by weighing lithium chloride powder (manufactured by Mitsuwa Chemical Co., Ltd., purity 99.5%), lithium bromide powder (manufactured by Sigma-Aldrich, purity 99.995%), lithium iodide powder (manufactured by Tokyo Chemical Industry Co., Ltd., purity 99.9%), and mixing them in a mortar. The obtained raw material mixture was placed in a carbon container under a nitrogen atmosphere containing sulfur element (manufactured by Sigma-Aldrich, purity 99.998%) as an S element source and having a dew point of −50° C. or less, and then placed in an electric furnace inside a glove box and heated at a pressure of gauge pressure +1 kPa and a temperature of 750° C. for 1 hour to obtain a molten material (Step 1). Next, the tip of the vessel was heated to melt the melt, and the molten material was poured onto twin rolls at an outflow rate that did not cause temperature unevenness, and cooled to room temperature at a cooling rate of 500°C / sec to obtain glass (Step 2). The pressure at this time was (gauge pressure + 1 kPa), and the cooling rate was adjusted by the outflow rate of the melt, the roll gap of the twin rolls, and the rotation speed.

[0122] Example 18: Lithium sulfide powder (manufactured by Albemarle, purity 99.9%), diphosphorus pentasulfide powder (manufactured by Perimeter, purity 95 to 100%), and SiS were mixed together in the composition ratio shown in Table 1. ２ A raw material mixture was obtained by weighing lithium chloride powder (manufactured by Mitsuwa Chemical Co., Ltd., purity 99%) and lithium chloride powder (manufactured by Sigma-Aldrich, purity 99.995%) and mixing them in a mortar. 1 g of the raw material mixture was placed in a zirconia pot together with 500 zirconia balls having a diameter of 4 mm in a nitrogen atmosphere glove box, and the pot was completely sealed. Mechanical milling was performed for 20 hours in a planetary ball mill (manufactured by Fritsch, P-7) at a rotation speed of 510 rpm, and a sample of Example 18 was obtained.

[0123] <Evaluation> <Glass Composition> The obtained glass was weighed in a glove box and dissolved in an alkaline aqueous solution, and composition analysis was performed for each element. Specifically, P, S, Sn, Sb, Si, Ge, Ga, Al, Mg, Ca, Sr, Ba, and Se were analyzed by ICP atomic emission spectroscopy (apparatus: Hitachi High-Tech Science Corporation, model PS3520UVDDII). Li was analyzed by atomic absorption spectroscopy (apparatus: Hitachi High-Tech Corporation, model ZA3300; when measuring Li, CsCl was added to the solution to make the concentration 0.1%). Cl, Br, and I were analyzed by ion chromatography (apparatus: Thermo Fisher Scientific, model ICS-2100 (column: AS11HC), H ２ O ２ A small amount of the solution was added, diluted with ultrapure water, and then the measurement was carried out.

[0124] The results are shown in "Glass composition (atomic %)" in Table 1. In all examples, the composition of the obtained glass did not deviate significantly from the composition of the raw material mixture.

[0125] <Physical Properties: Lithium Ion Conductivity> The obtained glass was crushed in a mortar and then passed through a 100 μm sieve to obtain a powder with an average particle size (D50) of approximately 20 μm, which was used as a sample. The sample was compressed under a pressure of 380 MPa to prepare a measurement sample, and measured using an AC impedance measuring device (potentiostat / galvanostat VSP, manufactured by Bio-Logic Sciences Instruments). The measurement conditions were a measurement frequency of 100 Hz to 1 MHz, a measurement voltage of 100 mV, and a measurement temperature of 25°C, and the lithium ion conductivity was calculated from the obtained Nyquist plot. The results are shown in the "σ" column in the "Physical Properties" section of Table 1. ２５ (mS / cm)".

[0126] <Physical Properties: Glass Transition Point> The obtained glass was measured using differential scanning calorimetry (DSC) at a rate of 10°C / min. The temperature at the first inflection point in the obtained DSC chart was determined as the glass transition point. The results are shown in "Tg (°C)" in the "Physical Properties" section of Table 1. Note that the same measurement was also performed on the sample of Example 18, and it was found that it did not have a glass transition point.

[0127] <Physical properties: H ２ The obtained glass was crushed in a mortar and then passed through a 100 μm sieve to obtain a powder with an average particle size (D50) of 10 to 20 μm, which was used as a sample. 10 mg of the sample was exposed to the atmosphere with a humidity controlled to a dew point of −30° C. for 1 hour, and the amount of hydrogen sulfide (H ２ S) The amount of generation was monitored, and the amount of generation per 1 g of sample was calculated as H ２ The amount of sulfur generated was calculated as (mL / g). The results are shown in Table 1 under "Physical Properties" under "H ２ In Table 1, "H ２ The "-" in the result of "Amount of S generated (mL / g)" indicates that it was not measured.

[0128]

[0129] From the above results, it was found that the glass according to this embodiment became glass even when the composition was such that crystals would be formed by conventional mechanical milling. Furthermore, the glass according to this embodiment was able to achieve a high lithium ion conductivity of 2 mS / cm or more while in a glassy state. In particular, it was suggested that the glass according to this embodiment can achieve a higher lithium ion conductivity by increasing the content of I. Furthermore, the glass according to this embodiment exhibited a high H ２ It was found that the amount of sulfur generated was small and that the glasses also had high water resistance. It was also suggested that the glasses of Examples 5 and 17, for which water resistance was not evaluated, had similarly high water resistance because high homogeneity was achieved without residues such as residual sulfur or unreacted raw materials by melting the raw material mixture and then quenching it.

[0130] Although various embodiments have been described above, it goes without saying that the present invention is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present invention. Furthermore, the components of the above embodiments may be combined in any manner as long as they do not deviate from the spirit of the invention.

[0131] In addition, this application is a Japanese patent application filed on September 28, 2023 (Patent Application No. 2023-168392), a Japanese patent application filed on September 28, 2023 (Patent Application No. 2023-168395), and a Japanese patent application filed on March 29, 2024 (Patent Application No. 2024-057517), the contents of which are incorporated by reference into this application.

Claims

1. A glass containing Li and P as elements constituting a cationic component, and S as an element constituting an anionic component, with a composition, expressed in atomic %, of Li: 30-42% and P: 5-16%, having a glass transition point of 110-300°C, and a lithium ion conductivity at 25°C of 2 mS / cm or more.

2. The glass according to claim 1, further comprising at least one element selected from the group consisting of Sn, Sb, Si, Ge, Ga, Al, B, C, Mg, Ca, Sr, and Ba as an element constituting the cationic component.

3. The glass according to claim 1, further comprising at least one element selected from the group consisting of F, Cl, Br, I, O, Se, N, and C as an element constituting the anion component.

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

5. A sulfide solid electrolyte comprising the crystallized glass according to claim 4.

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

7. A solid electrolyte layer comprising the sulfide solid electrolyte according to claim 5.

8. A lithium ion secondary battery comprising the sulfide solid electrolyte according to claim 5.

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