Sulfide solid electrolyte, method for producing sulfide solid electrolyte, positive electrode for electricity storage element, and electricity storage element

Abstract

One aspect of the present invention has a crystal structure, and contains at least one element A selected from the group consisting of lithium element, sodium element, and potassium element, phosphorus element, at least one element M selected from the group consisting of aluminum element and boron element, nitrogen element, and at least one halogen element, the molar ratio (A / P) of the content of the element A to the content of the element phosphorus is less than 3.74, and the molar ratio (N / P) of the content of the element nitrogen to the content of the element phosphorus is less than 0.33.

Description

Technical Field

[0001] This invention relates to sulfide solid electrolytes, methods for manufacturing sulfide solid electrolytes, positive electrodes for energy storage devices, and energy storage devices. Background Technology

[0002] Lithium-ion rechargeable batteries are widely used in personal computers, communication terminals, automobiles, and other electronic devices due to their high energy density. These batteries typically consist of a pair of electrodes electrically isolated by a separator and a non-aqueous electrolyte between them. Charging and discharging are achieved through the exchange of lithium ions between the two electrodes. In addition to lithium-ion rechargeable batteries, capacitors, such as lithium-ion capacitors, are also widely used as energy storage components.

[0003] In recent years, the use of solid electrolytes such as sulfide solid electrolytes to replace non-aqueous electrolytes obtained by dissolving electrolyte salts in liquids such as organic solvents has been proposed as energy storage elements for non-aqueous electrolytes.

[0004] Patent Document 1 describes a sulfide solid electrolyte having a crystal structure, which, as constituent elements, contains one or more divalent elements A, one or more halogen elements X, and nitrogen, wherein the divalent element A and the halogen element X are compounds A composed of these elements. 0.5 The combination where the hydration energy of X is greater than that of LiI.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: International Publication No. 2020 / 045634 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] Patent Document 1 describes how the presence of nitrogen in a sulfide solid electrolyte can suppress hydration reactions with low reversibility. However, the inventors have learned that the presence of nitrogen in the sulfide solid electrolyte sometimes leads to a decrease in oxidation resistance.

[0010] The present invention was made based on the above-described circumstances, and its object is to provide a sulfide solid electrolyte with high oxidation resistance, a method for manufacturing such a sulfide solid electrolyte, and a positive electrode and a storage element using such a sulfide solid electrolyte.

[0011] Methods for solving problems

[0012] One aspect of the present invention provides a sulfide solid electrolyte having a crystal structure containing at least one element A selected from the group consisting of lithium, sodium and potassium, phosphorus, at least one element M selected from the group consisting of aluminum and boron, nitrogen, and at least one halogen element, wherein the molar ratio (A / P) of the content of element A to the content of phosphorus is less than 3.74, and the molar ratio (N / P) of the content of nitrogen to the content of phosphorus is less than 0.33.

[0013] Another aspect of the present invention provides a method for manufacturing a sulfide solid electrolyte, comprising the step of processing a composition containing at least one element A selected from the group consisting of lithium, sodium, and potassium, phosphorus, at least one element M selected from the group consisting of aluminum and boron, nitrogen, and at least one halogen element, wherein the molar ratio (A / P) of the content of element A to the content of phosphorus is less than 3.74, and the molar ratio (N / P) of the content of nitrogen to the content of phosphorus is less than 0.33.

[0014] Another aspect of the present invention provides a sulfide solid electrolyte manufactured by another aspect of the present invention.

[0015] Another aspect of the present invention provides an energy storage element whose positive electrode contains a sulfide solid electrolyte of one aspect of the present invention.

[0016] Another aspect of the energy storage element of the present invention contains a sulfide solid electrolyte of one aspect of the present invention.

[0017] Invention Effects

[0018] According to any aspect of the present invention, it is possible to provide a sulfide solid electrolyte with high oxidation resistance, a method for manufacturing such a sulfide solid electrolyte, and a positive electrode and a storage element using such a sulfide solid electrolyte. Attached Figure Description

[0019] [ Figure 1 ] Figure 1 This is a schematic cross-sectional view of an all-solid-state battery as one embodiment of the energy storage element of the present invention.

[0020] [ Figure 2 ] Figure 2 This is a schematic diagram showing an energy storage device constructed by assembling multiple energy storage elements according to one embodiment of the present invention. Detailed Implementation

[0021] First, the sulfide solid electrolyte, the method for manufacturing the sulfide solid electrolyte, and the positive electrode and the energy storage element using such a sulfide solid electrolyte will be described in this specification.

[0022] [1] The sulfide solid electrolyte of one aspect of the present invention has a crystal structure and contains at least one element A selected from the group consisting of lithium, sodium and potassium, phosphorus, at least one element M selected from the group consisting of aluminum and boron, nitrogen, and at least one halogen element, wherein the molar ratio (A / P) of the content of the element A to the content of the phosphorus is less than 3.74, and the molar ratio (N / P) of the content of the nitrogen to the content of the phosphorus is less than 0.33.

[0023] The sulfide solid electrolyte described above [1] has high oxidation resistance. That is, even when the sulfide solid electrolyte described above [1] is used as a positive electrode, the coulombic efficiency of the energy storage element using such a positive electrode is not easily reduced. The reason for this effect is uncertain, but the following reason is speculated. The sulfide solid electrolyte described above [1] contains nitrogen and at least one element M selected from the group consisting of aluminum. Therefore, it is believed that a structure with high oxidation resistance can be formed in the sulfide solid electrolyte described above [1] by the presence of nitrogen and element M. As such a structure, an oxidation-resistant coating (protective layer) containing nitrogen and element M at grain boundaries can be considered, for example. In addition, it is believed that such a structure is difficult to maintain when the content of at least one element A selected from the group consisting of lithium, sodium and potassium or nitrogen is excessive. That is, it is speculated that when the content of nitrogen and element M is contained and the molar ratio of element A to phosphorus (A / P) and the molar ratio of nitrogen to phosphorus (N / P) are within the above range, the oxidation resistance of the sulfide solid electrolyte is improved.

[0024] It should be noted that the presence of a crystalline structure can be confirmed by powder X-ray diffraction. That is, in this invention, "having a crystalline structure" means that, in powder X-ray diffraction, peaks of the crystalline structure from the solid electrolyte are observed in the X-ray diffraction pattern. The sulfide solid electrolyte described above [1] may contain an amorphous portion. The powder X-ray diffraction is performed by the following steps. Under an argon atmosphere with a dew point below -50°C, the sulfide solid electrolyte powder to be measured is filled into a gas-tight X-ray diffraction sample holder. The powder X-ray diffraction is performed using an X-ray diffraction apparatus (Rigaku's "MiniFlex II"). The X-ray source is CuKα rays, the tube voltage is 30kV, the tube current is 15mA, and the diffracted X-rays are detected by a high-speed one-dimensional detector (model: D / teX Ultra 2) after passing through a Kβ filter with a thickness of 30μm. The sampling width is 0.01°, the scanning speed is 5° / min, the divergence slit width is 0.625°, the light-receiving slit width is 13mm (OPEN), and the scattering slit width is 8mm.

[0025] [2] In the sulfide solid electrolyte described in [1] above, the element M may include aluminum.

[0026] [3] In the sulfide solid electrolyte described in [1] or [2] above, the halogen element may include bromine or iodine.

[0027] [4] The sulfide solid electrolyte described in any one of [1] to [3] above can be represented by the following formula (1).

[0028] A a PM b S c N d X e Y f ···(1)

[0029] In equation (1) above, A is at least one element selected from the group consisting of Li, Na, and K. M is at least one element selected from the group consisting of Al and B. X is at least one element selected from the group consisting of F, Cl, Br, and I. Y is at least one element other than A, P, S, M, N, and X. a, b, c, d, e, and f satisfy 2≤a<3.74, 0.01≤b≤1, 2≤c≤6, 0.01≤d<0.33, 0.01≤e≤1, and 0≤f≤1, respectively.

[0030] The sulfide solid electrolytes described in [2] to [4] above are preferred embodiments of the present invention, have higher oxidation resistance, and are useful as sulfide solid electrolytes.

[0031] [5] Another aspect of the method for manufacturing a sulfide solid electrolyte of the present invention includes the step of processing a composition containing at least one element A selected from the group consisting of lithium, sodium and potassium, phosphorus, at least one element M selected from the group consisting of aluminum and boron, nitrogen, and at least one halogen element, wherein the molar ratio (A / P) of the content of the element A to the content of the phosphorus is less than 3.74, and the molar ratio (N / P) of the content of the nitrogen to the content of the phosphorus is less than 0.33.

[0032] According to the manufacturing method of sulfide solid electrolyte described above [5], it is possible to manufacture sulfide solid electrolyte with high oxidation resistance.

[0033] It should be noted that "composition" refers to a mixture of two or more compounds or elements (hereinafter, compounds and elements are also collectively referred to as compounds, etc.). The composition as a whole, that is, any compound contained in the composition, may contain element A, phosphorus, element M, nitrogen, and halogen. Alternatively, the composition may contain compounds that do not contain any one of element A, phosphorus, element M, nitrogen, and halogen.

[0034] [6] In the method for manufacturing the sulfide solid electrolyte described in [5] above, the composition may contain A α M β N represents the compound (where A is element A, M is element M, and α and β are stoichiometric values ​​assigned according to the type of element M).

[0035] In the method for manufacturing the sulfide solid electrolyte described above [6], since the composition contains A α M β The compound represented by N can therefore suppress the release of nitrogen from the composition during the manufacture of sulfide solid electrolytes. Therefore, the nitrogen content in the composition can be controlled with high precision. That is, by including the compound in the composition, the nitrogen content relative to the phosphorus content can be easily controlled within the aforementioned range, thus enabling the reliable and easy manufacture of highly oxidizing sulfide solid electrolytes.

[0036] [7] Another aspect of the present invention, the sulfide solid electrolyte, can be manufactured by the manufacturing method of the sulfide solid electrolyte described in [5] or [6] above.

[0037] The sulfide solid electrolyte described above [7] has high oxidation resistance.

[0038] [8] In another aspect of the present invention, the positive electrode of the energy storage element contains the sulfide solid electrolyte described in any one of [1] to [4] and [7] above.

[0039] The positive electrode for the energy storage element described above [8] contains a sulfide solid electrolyte with high oxidation resistance, which can improve the performance of the energy storage element using the positive electrode for the energy storage element described above [8].

[0040] [9] Another aspect of the energy storage element of the present invention contains the sulfide solid electrolyte described in any one of [1] to [4] and [7] above.

[0041] The energy storage element described above [9] uses a sulfide solid electrolyte with high oxidation resistance, thus enabling it to perform well.

[0042] The following describes in detail one embodiment of the present invention: a sulfide solid electrolyte, a method for manufacturing a sulfide solid electrolyte, a positive electrode for a storage element, a storage element, a method for manufacturing a storage element, a storage device, and other embodiments. It should be noted that the names of the constituent components (elements) used in each embodiment sometimes differ from the names of the constituent components (elements) used in the prior art. Furthermore, element names are sometimes represented by element symbols.

[0043] <Sulfide Solid Electrolytes>

[0044] The sulfide solid electrolyte of one embodiment of the present invention has a crystalline structure. Furthermore, the sulfide solid electrolyte has a predetermined elemental composition as described later. The sulfide solid electrolyte exhibits high oxidation resistance. The sulfide solid electrolyte typically possesses lithium-ion conductivity, sodium-ion conductivity, or potassium-ion conductivity. The sulfide solid electrolyte preferably possesses lithium-ion conductivity. The sulfide solid electrolyte can also exhibit high ionic conductivity.

[0045] (Crystal Structure)

[0046] The sulfide solid electrolyte preferably contains a high ionic conductivity phase (HICP) as its crystal structure. HICP is a specific crystal structure exhibiting diffraction peaks in the range of 19.9°±0.5° and 29.3°±0.5° in CuKα X-ray diffraction patterns. When this sulfide solid electrolyte possesses diffraction peaks from HICP, it exhibits good ionic conductivity.

[0047] One embodiment of the sulfide solid electrolyte of the present invention may have a crystal structure other than HICP. Examples of other crystal structures include LGPS type, argentite-germanium sulfide type, and Li7P3S.11 Thio-LISICON series, etc. This sulfide solid electrolyte can also have an amorphous portion.

[0048] (composition)

[0049] This sulfide solid electrolyte contains at least one element A selected from the group consisting of lithium, sodium, and potassium; phosphorus; at least one element M selected from the group consisting of aluminum and boron; nitrogen; and at least one halogen element X. Additionally, this sulfide solid electrolyte contains sulfur as a constituent element. The constituent elements are described below.

[0050] Element A is at least one selected from the group consisting of lithium, sodium, and potassium. Element A preferably includes lithium, and more preferably lithium.

[0051] The upper limit of the molar ratio (A / P) of element A relative to phosphorus content is less than 3.74, preferably 3.72, more preferably 3.70, and even more preferably 3.68. The lower limit of the molar ratio (A / P) is preferably 3.00, more preferably 3.20, even more preferably 3.40, and even more preferably 3.60. The molar ratio (A / P) can be a range formed by combining any of the above lower limits and any of the above upper limits. By setting the molar ratio (A / P) to the above range, oxidation resistance can be improved.

[0052] Element M is selected from at least one element chosen from the group consisting of aluminum and boron. It is believed that this sulfide solid electrolyte, by including element M along with nitrogen, forms a structure with high oxidation resistance. Element M preferably includes aluminum, and more preferably aluminum.

[0053] The lower limit of the molar ratio (M / P) of element M relative to phosphorus is preferably 0.01, more preferably 0.02, and even more preferably 0.03. The upper limit of the molar ratio (M / P) is preferably 0.15, more preferably 0.10, and even more preferably 0.05. By making the molar ratio (M / P) below the above-mentioned upper limit, the ionic conductivity of the sulfide solid electrolyte can be improved. The molar ratio (M / P) can be a range formed by combining any of the above-mentioned lower limit and any of the above-mentioned upper limit.

[0054] The upper limit of the molar ratio (N / P) of nitrogen to phosphorus is less than 0.33, preferably 0.30, more preferably 0.25, further preferably 0.20, even more preferably 0.15, and particularly preferably 0.10. The lower limit of the molar ratio (N / P) is preferably 0.01, more preferably 0.02, further preferably 0.04, and even more preferably 0.06. The molar ratio (N / P) can be a range formed by combining any of the above lower limits and any of the above upper limits. By setting the molar ratio (N / P) to the above range, oxidation resistance can be improved. Furthermore, because the portion of the sulfide solid electrolyte in contact with water becomes alkaline, the generation of hydrogen sulfide is easily suppressed.

[0055] Examples of halogen elements X include fluorine, chlorine, bromine, and iodine. Halogen element X preferably includes bromine or iodine, more preferably includes both bromine and iodine, and even more preferably includes both bromine and iodine.

[0056] The lower limit of the molar ratio (X / P) of halogen element X to phosphorus element is preferably 5.20, more preferably 0.56, further preferably 0.60, and even more preferably 0.64. The upper limit of the molar ratio (X / P) is preferably 0.82, more preferably 0.78, further preferably 0.74, and even more preferably 0.70. The molar ratio (X / P) can be a range formed by combining any of the above lower limits and any of the above upper limits.

[0057] The molar ratio ((Br+I) / X) of the total content of bromine and iodine relative to the total content of halogen element X is preferably 0.5 or more, more preferably 0.7 or more, and even more preferably 0.9 or more. The molar ratio ((Br+I) / X) can substantially be 1.0.

[0058] The lower limit of the molar ratio (Br / P) of bromine content relative to phosphorus content is preferably 0.32, more preferably 0.34, further preferably 0.36, and even more preferably 0.38. The upper limit of the molar ratio (Br / P) is preferably 0.48, more preferably 0.46, further preferably 0.44, and even more preferably 0.42. The molar ratio (Br / P) can be a range formed by combining any of the above lower limits and any of the above upper limits.

[0059] The lower limit of the molar ratio (I / P) of iodine to phosphorus is preferably 0.20, more preferably 0.22, further preferably 0.24, and even more preferably 0.26. The upper limit of the molar ratio (I / P) is preferably 0.34, more preferably 0.32, further preferably 0.30, and even more preferably 0.28. The molar ratio (I / P) can be a range formed by combining any of the above lower limits and any of the above upper limits.

[0060] The lower limit of the molar ratio (S / P) of sulfur content relative to phosphorus content is preferably 3.20, more preferably 3.40, further preferably 3.60, and even more preferably 3.80. The upper limit of the molar ratio (S / P) is preferably 4.80, more preferably 4.60, further preferably 4.40, and even more preferably 4.20. The molar ratio (S / P) can be a range formed by combining any of the above lower limits and any of the above upper limits.

[0061] In one embodiment of the present invention, the sulfide solid electrolyte may further contain element Y other than element A, phosphorus, element M, nitrogen, halogen element X, and sulfur. Examples of other element Y include oxygen. The molar ratio (Y / P) of the content of the aforementioned other element Y in the sulfide solid electrolyte relative to the content of phosphorus is sometimes preferably 0 or more and 1 or less, sometimes more preferably 0.1 or less, and further more preferably 0.01 or less.

[0062] The composition of the sulfide solid electrolyte according to one embodiment of the present invention is preferably a combination of lithium, phosphorus, element M, nitrogen as element A, bromine and sulfur as halogen element X; a combination of lithium, phosphorus, element M, nitrogen as element A, iodine and sulfur as halogen element X; and any one of the following: lithium, phosphorus, element M, nitrogen as element A, bromine and iodine as halogen element X, and sulfur. More preferably, it is a combination of lithium, phosphorus, element M, nitrogen as element A, bromine and iodine as halogen element X, and sulfur. In addition to the above-described element combinations, the sulfide solid electrolyte may also contain any other element Y. The preferred content of each element in the sulfide solid electrolyte having the above-described element combinations is also the same as described above.

[0063] The sulfide solid electrolyte of one embodiment of the present invention is preferably represented by the following formula (1).

[0064] A a PM b S c N d X e Yf ···(1)

[0065] In the above formula (1), A is at least one element selected from the group consisting of Li, Na, and K. M is at least one element selected from the group consisting of Al and B. X is at least one element selected from the group consisting of F, Cl, Br, and I. Y is at least one element other than A, P, S, M, N, and X, and a, b, c, d, e, and f satisfy 2≤a<3.74, 0.01≤b≤1, 2≤c≤6, 0.01≤d<0.33, 0.01≤e≤1, and 0≤f≤1, respectively.

[0066] In one embodiment of the present invention, the sulfide solid electrolyte has the composition represented by the above formula (1), and the oxidation resistance is further improved. In the above formula (1), A preferably contains Li, more preferably Li. M preferably contains Al, more preferably Al. X preferably contains Br and I, more preferably Br and I. The preferred ranges of a, b, c, d, e, and f are the same as the preferred ranges of the molar ratio of the content of each element to the content of the above phosphorus element. That is, the preferred range of a is the same as the preferred range of the above molar ratio (A / P), the preferred range of b is the same as the preferred range of the above molar ratio (M / P), the preferred range of c is the same as the preferred range of the above molar ratio (S / P), the preferred range of d is the same as the preferred range of the above molar ratio (N / P), the preferred range of e is the same as the preferred range of the above molar ratio (X / P), and the preferred range of f is the same as the preferred range of the above molar ratio (Y / P).

[0067] (Physical properties, uses, etc.)

[0068] As an embodiment of the present invention, the lower limit of the ionic conductivity of the sulfide solid electrolyte at 25°C is preferably 1 mS / cm, more preferably 2 mS / cm, further preferably 3 mS / cm, even more preferably 4 mS / cm, and particularly preferably 5 mS / cm or 6 mS / cm. By ensuring that the ionic conductivity of the sulfide solid electrolyte at 25°C is above the aforementioned lower limit, the charge and discharge performance of the energy storage element incorporating the sulfide solid electrolyte can be improved. The upper limit of the aforementioned ionic conductivity is not particularly limited; for example, it can be 20 mS / cm, or it can be 10 mS / cm.

[0069] The ionic conductivity of the sulfide solid electrolyte according to one embodiment of the present invention is determined by measuring AC impedance using the following method. Under an argon atmosphere with a dew point below -50°C, 120 mg of sample powder is added to a powder forming apparatus with an inner diameter of 10 mm, and then uniaxially pressurized at a pressure below 50 MPa using a hydraulic press. After pressure release, 120 mg of SUS316L powder, serving as a current collector, is added to the upper surface of the sample, and uniaxial pressing is performed again at a pressure below 50 MPa using a hydraulic press. Next, 120 mg of SUS316L powder, serving as a current collector, is added to the lower surface of the sample, and uniaxial pressing is performed at 360 MPa for 5 minutes, thereby obtaining particles for ionic conductivity measurement. These particles are inserted into an HS cell manufactured by Hosen Chemical Co., Ltd., and AC impedance is measured at a predetermined temperature. The measurement conditions are set as follows: applied voltage amplitude 20 mV, frequency range 1 MHz to 100 mHz, and measurement temperature 25°C.

[0070] The shape of the sulfide solid electrolyte in one embodiment of the present invention is not particularly limited, and it is usually granular, blocky, etc. This sulfide solid electrolyte is suitable for use as an electrolyte in energy storage devices such as lithium-ion secondary batteries, especially lithium-ion energy storage devices. It is particularly suitable for use as an electrolyte in all-solid-state batteries. It should be noted that this sulfide solid electrolyte can be used as a positive electrode, separator, negative electrode, etc., in energy storage devices. As described above, this sulfide solid electrolyte is suitable for use as a sulfide solid electrolyte for positive electrodes due to its high oxidation resistance.

[0071] <Methods for Manufacturing Sulfide Solid Electrolytes>

[0072] A method for manufacturing a sulfide solid electrolyte according to one embodiment of the present invention includes a step of processing a composition containing at least one element A selected from the group consisting of lithium, sodium, and potassium, phosphorus, at least one element M selected from the group consisting of aluminum and boron, nitrogen, and at least one halogen element X. It should be noted that the above composition typically also contains sulfur. According to this method for manufacturing a sulfide solid electrolyte, a sulfide solid electrolyte with high oxidation resistance can be manufactured. The sulfide solid electrolyte manufactured by this method is the same as the sulfide solid electrolyte of one embodiment of the present invention described above.

[0073] (Composition)

[0074] In a method for manufacturing a sulfide solid electrolyte according to one embodiment of the present invention, the composition used as a raw material typically includes sulfur in addition to element A, phosphorus, element M, nitrogen, and halogen element X. The composition is typically a mixture of two or more compounds containing at least one of element A, phosphorus, element M, nitrogen, halogen element X, and sulfur. Any compound contained in the composition (mixture) may contain element A, phosphorus, element M, nitrogen, halogen element X, and sulfur. A single compound may contain two or more of element A, phosphorus, element M, nitrogen, halogen element X, and sulfur. For example, Li₂S (described later) can be a compound containing lithium (element A) and sulfur, and P₂S₅ (described later) can be a compound containing phosphorus and sulfur. The composition may also contain compounds that do not contain any of element A, phosphorus, element M, nitrogen, halogen element X, and sulfur.

[0075] In the above composition, the molar ratio (A / P) of element A to phosphorus is less than 3.74. Furthermore, the molar ratio (N / P) of nitrogen to phosphorus is less than 0.33. The preferred contents of each element in the above composition are the same as the preferred contents of each element in the sulfide solid electrolyte of one embodiment of the present invention.

[0076] Examples of compounds containing phosphorus include P2S3, P2S5, P2O5, P3N5, and elemental phosphorus. Among these, P2S3 and P2S5 are preferred, and P2S5 is more preferred. A single phosphorus-containing compound may be used, or two or more may be used in combination.

[0077] Examples of compounds containing halogen element X include compounds of element A, sulfur, phosphorus, etc., with halogen element X being preferred, and compounds of element A and halogen element X being more preferred. Examples of compounds of lithium and halogen element X include LiF, LiCl, LiBr, and LiI. A single compound containing halogen element X may be used, or two or more may be used in combination.

[0078] As compounds containing nitrogen, compounds containing nitrogen and element M are preferred, and compounds containing A are even more preferred. α M β N represents a compound (where A is element A, M is element M, and α and β are stoichiometric values ​​assigned based on the type of element M). From A α M βThe compound represented by N can suppress the release of nitrogen from the above composition during the processing steps described later. This is believed to be because, for example, as described in Patent Document 1, when using a raw material compound containing nitrogen and element M, the nitrogen defect formation energy is high, making it difficult to generate nitrogen defects and nitrogen gas during synthesis. Therefore, the nitrogen content in the above composition can be controlled with high precision. That is, by including A in the above composition... α M β The compounds represented by N can easily control the molar ratio (N / P) of nitrogen to phosphorus within the above range, thus enabling the reliable and easy manufacture of sulfide solid electrolytes with high oxidation resistance.

[0079] As a result of A α M β Compounds represented by N can include those containing lithium, nitrogen, and nitrogen (hereinafter also referred to as Li-MN compounds). Li-MN compounds can be manufactured according to the following steps: First, prepare Li3N and a nitride of nitrogen, and mix them using a mortar and pestle. Next, prepare particles of the mixed raw material compound. Then, heat-treat the particles to produce the Li-MN compound. It should be noted that the method for preparing Li-MN compounds is not limited to this; other methods can also be used. For example, the raw materials for Li-MN compounds can be any two or more compounds containing any one of lithium, nitrogen, or nitrogen. Li-MN compounds can also be produced by mechanical grinding. Li-MN compounds can also be prepared as substances for industrial manufacture and sale.

[0080] As a Li-MN-containing compound, a lithium complex nitride containing element M is preferred. Examples of lithium complex nitrides containing element M include Li 1.5 Al 0.5 N, Li 1.5 B 0.5 Lithium complex nitrides such as N are preferred. The lithium complex nitrides described above have a lower lithium content relative to nitrogen content, for example, than Li3N described later. Therefore, from the viewpoint of controlling the molar ratio (A / P) of nitrogen content to phosphorus content within the aforementioned range, the composition preferably includes the lithium complex nitride. Furthermore, by including the lithium complex nitride in the composition, a sulfide solid electrolyte in which hydrogen sulfide generation is suppressed can be produced. This is because, by including the lithium complex nitride in the composition, the resulting sulfide solid electrolyte reliably and readily contains a sufficient amount of nitrogen, making the contact portion with water alkaline, thereby preventing the generation of hydrogen sulfide. Among the lithium complex nitrides described above, Li is preferred. 1.5Al 0.5 N.

[0081] Other compounds containing nitrogen include, for example, Li3N, PN, P3N5, S4N4, S2N2, and S4N2. A single nitrogen-containing compound can be used alone, or two or more can be used in combination.

[0082] As compounds containing element M, compounds containing nitrogen and element M are preferred, and compounds containing A are even more preferred. α M β Compounds represented by N. Other compounds containing element M include oxides of element M, sulfides of element M, nitrides of element M, and alloys of atoms of element M and lithium atoms. Examples of sulfides of element M include Al₂S₃. Examples of nitrides of element M include AlN and BN. Compounds containing element M can be used alone or in combination of two or more.

[0083] Examples of compounds containing element A include halides of element A (such as LiF, LiCl, LiBr, LiI, etc.) and compounds containing element A. α M β N represents compounds (Li 1.5 Al 0.5 The following substances are preferred: N, Li₂S, Li₂O, Li₃N, Li₂CO₃, lithium metal, Na₂S, Na₂O, Na₃N, Na₂CO₃, sodium metal, K₂S, K₂O, K₃N, K₂CO₃, potassium metal, etc. Among these, Li₂S and Li₂O are preferred. 1.5 Al 0.5 N, LiBr, and LiI. Compounds containing element A can be used alone or in combination with two or more.

[0084] Examples of compounds containing sulfur include Li₂S, P₂S₃, P₂S₅, Al₂S₃, and elemental sulfur. Among these, Li₂S, P₂S₃, and P₂S₅ are preferred, and Li₂S and P₂S₅ are more preferred. A single sulfur-containing compound may be used, or two or more may be used in combination.

[0085] For example, as one embodiment, the above composition may contain Li2S, P2S5, and Li 1.5 Al 0.5 A combination of N, LiBr, and LiI, or a combination of Li2S, P2S5, and Li 1.5 Al 0.5 A composition consisting of N, LiBr and LiI.

[0086] (Processing steps)

[0087] In a method for manufacturing a sulfide solid electrolyte according to one embodiment of the present invention, the above-described composition is processed to obtain a sulfide solid electrolyte. Examples of such processing include obtaining an intermediate by mechanical grinding and then heating the intermediate. It should be noted that the method for obtaining the intermediate is not limited to this; methods other than mechanical grinding, such as melt quenching, may also be used.

[0088] Mechanical grinding can be either dry or wet, but wet grinding is preferred for more uniform mixing of raw materials such as compounds. Examples of mechanical grinding include container-driven mills, media-stirred mills, high-speed rotary mills, roller mills, and jet mills. Examples of container-driven mills include rotary mills, vibratory mills, and planetary mills. Examples of media-stirred mills include grinding mills and bead mills. Examples of high-speed rotary mills include hammer mills and disc mills. Among these, container-driven mills are preferred, and planetary mills are particularly preferred.

[0089] Intermediates obtained through mechanical grinding and other processes can have a crystalline structure, but are preferably so-called sulfide glasses. "Sulfide glass" refers to sulfide solid electrolytes containing amorphous structures. If the intermediate is a sulfide glass, sulfide solid electrolytes with few unstable crystalline phases such as Li2S and high elemental dispersion can be obtained.

[0090] Regarding heating, the intermediate obtained through mechanical grinding or the like is heated (heat treatment). This results in at least a portion of the intermediate crystallizing, preferably at least a portion crystallizing, into the aforementioned HICP sulfide solid electrolyte. Heating (heat treatment) can be performed under reduced pressure or under an inactive gas atmosphere. The preferred heating temperature range is, for example, 150°C or higher and 250°C or lower, more preferably 170°C or higher and 240°C or lower, and even more preferably 180°C or higher and 230°C or lower. By setting the heating temperature above the aforementioned lower limit, a sulfide solid electrolyte with sufficiently high crystallization and oxidation resistance can be obtained. Furthermore, by setting the heating temperature below the aforementioned upper limit, the precipitation of the low ionic conductivity phase (LICP) is suppressed, resulting in a sulfide solid electrolyte with high ionic conductivity. It should be noted that LICP is a specific crystal structure that has diffraction peaks in the range of diffraction angle 2θ in the range of 21.0°±0.5° and 28.0°±0.5° in the X-ray diffraction pattern using CuKα rays.

[0091] Positive electrode for energy storage components

[0092] The positive electrode (hereinafter also referred to as "positive electrode") for an energy storage element according to one embodiment of the present invention contains a sulfide solid electrolyte according to one embodiment of the present invention. This positive electrode contains a sulfide solid electrolyte according to one embodiment of the present invention with high oxidation resistance, thus improving the charge and discharge efficiency of the energy storage element when used in an energy storage element. The positive electrode includes a positive electrode substrate and a positive electrode active material layer disposed directly or through an intermediate layer on the positive electrode substrate. The positive electrode may have an intermediate layer between the positive electrode substrate and the positive electrode active material layer.

[0093] Other solid electrolytes besides the sulfide solid electrolyte of one embodiment of the present invention may also be used simultaneously at the positive electrode. Examples of other solid electrolytes include sulfide solid electrolytes, oxide solid electrolytes, dry polymer electrolytes, gel polymer electrolytes, quasi-solid electrolytes, etc., in addition to the sulfide solid electrolyte of one embodiment of the present invention, with sulfide solid electrolytes being preferred.

[0094] Examples of sulfide solid electrolytes other than sulfide solid electrolytes as one embodiment of the present invention include Li2S-P2S5, Li2S-P2S5-LiI, Li2S-P2S5-LiCl, Li2S-P2S5-LiBr, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-P2S5-Li3N, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, and Li2S-P2S5-Z. m S 2n (Where m and n are positive numbers, and Z is any one of Ge, Zn, and Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li x MO y (Where x and y are positive numbers, and M is any one of P, Si, Ge, B, Al, Ga, and In), Li6PS5Cl, Li 10 GeP2S 12 etc. Among them, the sulfide solid electrolyte other than the sulfide solid electrolyte in one embodiment of the present invention can preferably be a sulfide-germanium ore type solid electrolyte such as Li6PS5Cl.

[0095] The positive electrode substrate is conductive. Regarding whether it possesses "conductivity," the volume resistivity measured according to JIS-H-0505 (1975) is used as a metric to determine conductivity. -2The threshold value (Ω·cm) is used for determination. The material used as the positive electrode substrate is metal such as aluminum, titanium, tantalum, stainless steel, or their alloys. Among these, aluminum or aluminum alloys are preferred from the viewpoints of high potential resistance, high conductivity, and cost. Examples of positive electrode substrates include foil, vapor-deposited film, mesh, and porous materials; from a cost perspective, foil is preferred. Therefore, aluminum foil or aluminum alloy foil is preferred as the positive electrode substrate. Examples of aluminum or aluminum alloys include A1085, A3003, and AlN30 as specified in JIS-H-4000 (2014) or JIS-H-4160 (2006).

[0096] The average thickness of the positive electrode substrate is preferably 3 μm or more and 50 μm or less, more preferably 5 μm or more and 40 μm or less, even more preferably 8 μm or more and 30 μm or less, and particularly preferably 10 μm or more and 25 μm or less. By setting the average thickness of the positive electrode substrate within the above range, the strength of the positive electrode substrate can be improved, and the energy density per unit volume of the energy storage element can be increased. "Average thickness" is defined as the average value of the thickness measured at any 5 locations (hereinafter, the same applies to average thickness).

[0097] The interlayer is a layer disposed between the positive electrode substrate and the positive electrode active material layer. The interlayer reduces the contact resistance between the positive electrode substrate and the positive electrode active material layer by including conductive agents such as carbon particles. The composition of the interlayer is not particularly limited; for example, it may include a binder and a conductive agent.

[0098] The positive electrode active material layer comprises a positive electrode active material and a sulfide solid electrolyte. The positive electrode active material layer can be formed from a so-called positive electrode compound containing both the positive electrode active material and the sulfide solid electrolyte. The positive electrode active material layer may contain a mixture or composite comprising the positive electrode active material and the sulfide solid electrolyte, etc. The positive electrode active material layer may, as needed, contain any components such as conductive agents, binders, thickeners, and fillers. One or more of these arbitrary components may be substantially absent from the positive electrode active material layer.

[0099] As the positive electrode active material, it can be appropriately selected from known positive electrode active materials. For positive electrode active materials used in lithium-ion secondary batteries, materials capable of absorbing and releasing lithium ions are typically used. Examples of positive electrode active materials include lithium transition metal composite oxides with an α-NaFeO2-type crystal structure, lithium transition metal composite oxides with a spinel-type crystal structure, polyanionic compounds, chalcogenides, and sulfur. For example, Li[Li] can be used as a lithium transition metal composite oxide with an α-NaFeO2-type crystal structure. x Ni (1-x) O2 (0≤x<0.5), Li[Li x Ni γ Co (1-x-γ)]O2(0≤x<0.5, 0<γ<1, 0<1-x-γ), Li[Li x Co (1-x) O2 (0≤x<0.5), Li[Li x Ni γ Mn (1-x-γ) ]O2(0≤x<0.5, 0<γ<1, 0<1-x-γ), Li[Li x Ni γ Mn β Co (1-x-γ-β) ]O2(0≤x<0.5, 0<γ, 0<β, 0.5<γ+β<1, 0<1-x-γ-β), Li[Li x Ni γ Co β Al (1-x-γ-β) O2 (0≤x<0.5, 0<γ, 0<β, 0.5<γ+β<1, 0<1-x-γ-β), etc. As a lithium transition metal composite oxide with a spinel-type crystal structure, Li can be cited as an example. x Mn2O4, Li x Ni γ Mn (2-γ) Examples of polyanionic compounds include O4, LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4, Li3V2(PO4)3, Li2MnSiO4, and Li2CoPO4F. Examples of chalcogenides include titanium disulfide, molybdenum disulfide, and molybdenum dioxide. Atoms or polyanions in these materials can be partially replaced by atoms or anions composed of other elements. The surface of these materials can also be coated with other materials (e.g., LiNbO3). In the positive electrode active material layer, one of these materials can be used alone, or two or more can be used in combination.

[0100] As the positive electrode active material, a lithium transition metal composite oxide is preferred; more preferably, a lithium transition metal composite oxide containing at least one of nickel, cobalt, and manganese is preferred; even more preferably, a lithium transition metal composite oxide containing at least two of nickel, cobalt, and manganese is preferred; and still more preferably, a lithium transition metal composite oxide containing nickel, cobalt, and manganese is preferred. This lithium transition metal composite oxide preferably has an α-NaFeO2 type crystal structure. By using such a lithium transition metal composite oxide, energy density and other properties can be improved.

[0101] The positive electrode active material is typically in the form of particles (powder). The average particle size of the positive electrode active material is preferably 0.1 μm or more and 20 μm or less. By setting the average particle size of the positive electrode active material to the lower limit mentioned above, the manufacture or processing of the positive electrode active material becomes easier. By setting the average particle size of the positive electrode active material to the upper limit mentioned above, the electronic conductivity of the positive electrode active material layer is improved. It should be noted that when using a composite of the positive electrode active material and other materials, the average particle size of the composite is used as the average particle size of the positive electrode active material. "Average particle size" refers to the value where the cumulative distribution based on the volumetric standard calculated according to JIS-Z-8819-2 (2001) is 50%, determined by laser diffraction scattering based on the particle size distribution obtained by diluting particles with solvent according to JIS-Z-8825 (2013).

[0102] To obtain powder with a predetermined particle size, pulverizers, classifiers, etc., can be used. Examples of pulverizing methods include using mortars, ball mills, sand mills, vibratory ball mills, planetary ball mills, jet mills, reverse jet mills, cyclone jet mills, or sieves. Wet pulverization, which involves the coexistence of water or organic solvents such as hexane, can also be used. As for classification methods, sieves, air classifiers, etc., can be used in both dry and wet processes as needed.

[0103] The content of the positive electrode active material in the positive electrode active material layer is preferably 10% by mass or more and 95% by mass or less, more preferably 30% by mass or more and 90% by mass or less, even more preferably 50% by mass or more and 85% by mass or less, and the lower limit is more preferably 60% by mass, and even more preferably 70% by mass. By setting the content of the positive electrode active material within the above range, the discharge capacity of the energy storage element can be increased.

[0104] The content of all solid electrolytes in the positive electrode active material layer is preferably 5% by mass or more and 50% by mass or less, more preferably 10% by mass or more and 40% by mass or less, and even more preferably 15% by mass or more and 30% by mass or less. As an embodiment of the present invention, the content of the sulfide solid electrolyte relative to all solid electrolytes in the positive electrode active material layer is preferably 5% by mass or more and 100% by mass or less, more preferably 10% by mass or more and 100% by mass or less, and even more preferably 20% by mass or more and 100% by mass or less. By setting the content of solid electrolytes within the above ranges, the discharge capacity of the energy storage element can be increased, etc.

[0105] Examples of composites consisting of a positive electrode active material and a solid electrolyte include composites in which the positive electrode active material and the solid electrolyte are chemically or physically bonded, and composites formed by mechanically combining the positive electrode active material and the solid electrolyte. These composites may contain both the positive electrode active material and the solid electrolyte within a single particle; examples include composites in which the positive electrode active material and the solid electrolyte are in a condensed state, and composites in which at least a portion of the surface of the positive electrode active material has a film containing the solid electrolyte.

[0106] A composite (composite particle) formed by coating at least a portion of the surface of positive electrode active material particles with a sulfide solid electrolyte according to one embodiment of the present invention is also a preferred embodiment of the present invention. By coating at least a portion of the surface of the positive electrode active material particles with the sulfide solid electrolyte according to one embodiment of the present invention, good ion conductivity can be achieved. Furthermore, the sulfide solid electrolyte according to one embodiment of the present invention is particularly useful as a solid electrolyte for coating positive electrode active materials due to its good oxidation resistance. The content of the sulfide solid electrolyte in this composite is preferably, for example, 1% by mass or more and 20% by mass or less, more preferably 3% by mass or more and 10% by mass or less. The content of this composite in the positive electrode active material layer is preferably, for example, 60% by mass or more and 95% by mass or less, more preferably 70% by mass or more and 90% by mass or less, and even more preferably 75% by mass or more and 85% by mass or less.

[0107] This composite (composite particles) can be manufactured, for example, by mixing particulate or powdered positive electrode active material and solid electrolyte while applying impact, compression, and shear forces. At this time, components other than the positive electrode active material and solid electrolyte can be further mixed to achieve composite formation. This composite formation process can be performed, for example, using a device equipped with a vortex (also known as a rotating blade, impeller, etc.). Specifically, the above process uses a mechanical mixing method that applies impact, compression, and shear forces to the mixture of positive electrode active material and solid electrolyte between the turbine and the wall of the container by rotating a turbine inside the container. The above process can be carried out in a dry or wet manner. Before performing the above process using a turbine-equipped device, the positive electrode active material and solid electrolyte can be premixed. Alternatively, the positive electrode active material and solid electrolyte can be separately introduced into the turbine-equipped device.

[0108] The positive electrode active material layer may comprise the composite (composite particles), other solid electrolytes, conductive agents, and binders. In this manner, the solid electrolyte constituting the composite and the other solid electrolytes may be sulfide solid electrolytes according to one embodiment of the present invention. Alternatively, the other solid electrolytes may be solid electrolytes other than sulfide solid electrolytes according to one embodiment of the present invention. For example, sulfide solid electrolytes other than those exemplified above and conventionally known sulfide solid electrolytes according to one embodiment of the present invention may be preferred.

[0109] There are no particular limitations on conductive agents, as long as they are materials with electrical conductivity. Examples of such conductive agents include carbon materials, metals, and conductive ceramics. Examples of carbon materials include graphite, non-graphite carbon, and graphene-based carbon. Examples of non-graphite carbon include carbon nanofibers, pitch-based carbon fibers, and carbon black. Examples of carbon black include furnace black, acetylene black, and Ketjen black. Examples of graphene-based carbon include graphene, carbon nanotubes, and fullerenes. Examples of conductive agents can be in powder or fibrous form. Conductive agents can be used alone or in combination with two or more materials. Furthermore, these materials can be combined. For example, a material formed by combining carbon black and carbon nanotubes can be used.

[0110] The content of the conductive agent in the positive electrode active material layer is preferably 0.5% by mass or more and 10% by mass or less, more preferably 1% by mass or more and 6% by mass or less, and the upper limit of the above-mentioned conductive agent content can be 5% by mass, 4% by mass or 3% by mass. By setting the content of the conductive agent within the above range, the energy density of the energy storage element can be improved.

[0111] Examples of adhesives include fluoropolymers (such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF)), thermoplastic resins such as polyethylene, polypropylene, polyacrylic acid, and polyimide; elastomers such as ethylene-propylene-diene rubber (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), and fluororubber; and polysaccharide polymers.

[0112] The binder content in the positive electrode active material layer is preferably 0.5% by mass or more and 10% by mass or less, more preferably 1% by mass or more and 6% by mass or less, and the upper limit of the binder content can be 5% by mass, 4% by mass or 3% by mass. By setting the binder content within the above range, the positive electrode active material can be stably maintained.

[0113] Examples of thickeners include polysaccharide polymers such as carboxymethyl cellulose (CMC) and methyl cellulose. When the thickener has functional groups that react with lithium, these functional groups can be deactivated beforehand through methylation or the like. In one embodiment of the present invention, the content of the thickener in the positive electrode active material layer may be less than 1% by mass, less than 0.1% by mass, or may be substantially free of thickener.

[0114] The filler is not particularly limited. Examples of fillers include polyolefins such as polypropylene and polyethylene; inorganic oxides such as silica, alumina, titanium dioxide, calcium oxide, strontium oxide, barium oxide, magnesium oxide, and aluminosilicates; hydroxides such as magnesium hydroxide, calcium hydroxide, and aluminum hydroxide; carbonates such as calcium carbonate; sparingly soluble ionic crystals such as calcium fluoride, barium fluoride, and barium sulfate; nitrides such as aluminum nitride and silicon nitride; talc, montmorillonite, boehmite, zeolite, apatite, kaolin, mullite, spinel, olivine, sericite, bentonite, and mica; and other mineral-derived materials or their synthetic forms. In one embodiment of the present invention, the filler content in the positive electrode active material layer may be less than 1% by mass, less than 0.1% by mass, or substantially no filler.

[0115] The positive electrode active material layer may also contain typical non-metallic elements such as B, N, P, F, Cl, Br, I, typical metallic elements such as Li, Na, Mg, Al, K, Ca, Zn, Ga, Ge, Sn, Sr, Ba, and transition metal elements such as Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, Nb, W as components other than the positive electrode active material, solid electrolyte, conductive agent, binder, thickener, and filler.

[0116] The average thickness of the positive electrode active material layer is preferably 30 μm or more and 1,000 μm or less, more preferably 60 μm or more and 500 μm or less. By making the average thickness of the positive electrode active material layer at or above the above lower limit, an energy storage device with high energy density can be obtained. By making the average thickness of the positive electrode active material layer at or below the above upper limit, miniaturization of the energy storage device can be achieved.

[0117] <Electronic Storage Components>

[0118] One embodiment of the energy storage element of the present invention contains a sulfide solid electrolyte of one embodiment of the present invention. As an example of an energy storage element according to one embodiment of the present invention, an all-solid-state battery will be described below. Figure 1The energy storage element 10 is an all-solid-state battery, a secondary battery consisting of a positive electrode 1 and a negative electrode 2 separated by an insulating layer 3. The positive electrode 1 has a positive electrode substrate 4 and a positive electrode active material layer 5, with the positive electrode substrate 4 forming the outermost layer of the positive electrode 1. The negative electrode 2 has a negative electrode substrate 7 and a negative electrode active material layer 6, with the negative electrode substrate 7 forming the outermost layer of the negative electrode 2. Figure 1 In the energy storage element 10 shown, a negative electrode active material layer 6, an isolation layer 3, a positive electrode active material layer 5, and a positive electrode substrate 4 are sequentially stacked on the negative electrode substrate 7.

[0119] The energy storage element 10 contains a sulfide solid electrolyte according to one embodiment of the present invention in at least one of the positive electrode 1, the negative electrode 2, and the isolation layer 3. More specifically, it contains a sulfide solid electrolyte according to one embodiment of the present invention in at least one of the positive electrode active material layer 5, the negative electrode active material layer 6, and the isolation layer 3. When the positive electrode 1 contains a sulfide solid electrolyte according to one embodiment of the present invention, the positive electrode 1 is the positive electrode for the energy storage element according to one embodiment of the present invention. Because the energy storage element 10 uses a sulfide solid electrolyte with high oxidation resistance, it can improve the performance of the energy storage element, such as charge and discharge efficiency and capacity retention rate.

[0120] The energy storage element 10 may also use other solid electrolytes besides the sulfide solid electrolyte of one embodiment of the present invention. Examples of other solid electrolytes include the solid electrolyte exemplified in the description of the positive electrode for the energy storage element of one embodiment of the present invention, with a sulfide solid electrolyte being preferred. Furthermore, one layer of the energy storage element 10 may contain multiple different solid electrolytes, or each layer may contain a different solid electrolyte.

[0121] (positive electrode)

[0122] The positive electrode 1 includes a positive electrode substrate 4 and a positive electrode active material layer 5 disposed directly on or separated from the positive electrode substrate 4 by an intermediate layer. In one embodiment of the present invention, the positive electrode 1 uses a positive electrode for an energy storage device according to an embodiment of the present invention.

[0123] (negative electrode)

[0124] The negative electrode 2 has a negative electrode substrate 7 and a negative electrode active material layer 6 disposed directly on the negative electrode substrate 7 or separated from it by an intermediate layer. The composition of the intermediate layer is not particularly limited, and can be selected from, for example, the composition exemplified by the positive electrode of an energy storage element according to one embodiment of the present invention.

[0125] The negative electrode substrate 7 is conductive. The material used for the negative electrode substrate 7 includes metals such as copper, nickel, stainless steel, nickel-plated steel, and aluminum, or their alloys, and carbonaceous materials. Copper or copper alloys are preferred. Examples of materials that can be used for the negative electrode substrate 7 include foil, vapor-deposited film, mesh, and porous materials; from a cost perspective, foil is preferred. Therefore, copper foil or copper alloy foil is preferred as the negative electrode substrate 7. Examples of copper foil include rolled copper foil and electrolytic copper foil.

[0126] The average thickness of the negative electrode substrate 7 is preferably 2 μm or more and 35 μm or less, more preferably 3 μm or more and 30 μm or less, even more preferably 4 μm or more and 25 μm or less, and particularly preferably 5 μm or more and 20 μm or less. By setting the average thickness of the negative electrode substrate 7 within the above range, the strength of the negative electrode substrate 7 can be improved, and the energy density per unit volume of the energy storage element 10 can be increased.

[0127] The negative electrode active material layer 6 contains a negative electrode active material. The negative electrode active material layer 6 can be formed from a so-called negative electrode compound containing the negative electrode active material. The negative electrode active material layer 6 can contain a solid electrolyte, or a mixture or complex of the negative electrode active material and a solid electrolyte, etc. The negative electrode active material layer 6 may, as needed, contain any components such as conductive agents, binders, thickeners, and fillers. The types and preferred contents of these components in the negative electrode active material layer 6 are the same as those of the components in the positive electrode active material layer 5 described above. One or more of these components may be substantially absent from the negative electrode active material layer 6.

[0128] The negative electrode active material layer 6 may also contain typical non-metallic elements such as B, N, P, F, Cl, Br, I, typical metallic elements such as Li, Na, Mg, Al, K, Ca, Zn, Ga, Ge, Sn, Sr, Ba, and transition metal elements such as Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, Ta, Hf, Nb, W as components other than the negative electrode active material, solid electrolyte, conductive agent, binder, thickener, and filler.

[0129] As the negative electrode active material, an appropriate selection can be made from known negative electrode active materials. For lithium-ion secondary batteries, materials capable of absorbing and releasing lithium ions are typically used. Examples of negative electrode active materials include metallic lithium; metals or half-metals such as Si and Sn; metal oxides or half-metal oxides such as Si oxide, Ti oxide, and Sn oxide; and Li₄Ti₅O₅. 12 LiTiO 2、Titanium oxides such as TiNb2O7; polyphosphate compounds; carbon materials such as silicon carbide, graphite, and non-graphite carbon (easily graphitized carbon or difficult-to-graphitize carbon). Among these materials, graphite and non-graphite carbon are preferred. In the negative electrode active material layer 6, one of these materials can be used alone, or two or more can be used in combination.

[0130] "Graphite" refers to the average lattice spacing (d) of the (002) plane determined by X-ray diffraction before or during charging and discharging. 002 Carbon materials with a wavelength greater than 0.33 nm and less than 0.34 nm are preferred. Examples of graphite include natural graphite and synthetic graphite. From the perspective of obtaining materials with stable physical properties, synthetic graphite is preferred.

[0131] "Non-graphite carbon" refers to the average lattice spacing (d) of the (002) plane determined by X-ray diffraction before or during charging and discharging. 002 Carbon materials are those with a wavelength of 0.34 nm or more and 0.42 nm or less. Examples of non-graphitic carbon include difficult-to-graphitize carbon and easily-graphitize carbon. Examples of non-graphitic carbon include materials derived from resins, petroleum asphalt or materials derived from petroleum asphalt, petroleum coke or materials derived from petroleum coke, plant materials, and materials derived from alcohols.

[0132] Here, "discharge state" refers to the state in which the carbon material, which serves as the negative electrode active material, is discharged in such a way that lithium ions that can be absorbed and released during charging and discharging are fully released. For example, in a half-cell that uses a negative electrode containing carbon material as the negative electrode active material as the working electrode and uses metallic lithium as the counter electrode, it is a state in which the open-circuit voltage is 0.7V or higher.

[0133] "Difficult-to-graphitize carbon" refers to the aforementioned d 002 Carbon materials with a wavelength of 0.36 nm or more and 0.42 nm or less.

[0134] "Easily graphitizable carbon" refers to the aforementioned d 002 It is a carbon material with a wavelength greater than 0.34 nm and less than 0.36 nm.

[0135] The negative electrode active material is typically in the form of particles (powder). The average particle size of the negative electrode active material can be, for example, set to 1 nm or more and 100 μm or less. When the negative electrode active material is a carbon material, a titanium oxide, or a polyphosphate compound, its average particle size can be 1 μm or more and 100 μm or less. When the negative electrode active material is Si, Sn, Si oxide, or Sn oxide, its average particle size can be 1 nm or more and 1 μm or less. By setting the average particle size of the negative electrode active material to the lower limit or above, the manufacturing or processing of the negative electrode active material becomes easier. By setting the average particle size of the negative electrode active material to the upper limit or below, the electronic conductivity of the negative electrode active material layer 6 is improved. To obtain powder with a predetermined particle size, a pulverizer, classifier, etc., can be used. The pulverizing method and classification method can be selected, for example, from the method exemplified in the positive electrode of a storage element according to one embodiment of the present invention. When the negative electrode active material is a metal such as lithium metal, the negative electrode active material layer 6 can be in foil form.

[0136] The content of the negative electrode active material in the negative electrode active material layer 6 is preferably 10% by mass or more and 100% by mass or less, more preferably 30% by mass or more and 95% by mass or less, and the lower limit is more preferably 50% by mass, and even more preferably 70% by mass. When the negative electrode active material is a metal such as lithium, the lower limit of the content of the negative electrode active material in the negative electrode active material layer 6 can be 95% by mass or 99% by mass. By setting the content of the negative electrode active material within the above range, the discharge capacity of the energy storage element 10 can be increased.

[0137] When the negative electrode active material layer 6 contains a solid electrolyte, the content of the solid electrolyte is preferably 5% by mass or more and 90% by mass or less, more preferably 20% by mass or more and 70% by mass or less, and there is also a case where the upper limit is more preferably 50% by mass. By setting the content of the solid electrolyte within the above range, the discharge capacity of the energy storage element 10 can be increased. When the negative electrode active material layer 6 uses a sulfide solid electrolyte according to one embodiment of the present invention, the content of the sulfide solid electrolyte according to one embodiment of the present invention relative to all solid electrolytes in the negative electrode active material layer 6 is preferably 50% by mass or more, more preferably 70% by mass or more, more preferably 90% by mass or more, and even more preferably substantially 100% by mass.

[0138] Regarding mixtures or complexes of negative electrode active materials and solid electrolytes, the positive electrode active material can be replaced with a negative electrode active material in the aforementioned mixtures or complexes of positive electrode active materials and solid electrolytes.

[0139] The average thickness of the negative electrode active material layer 6 is preferably 30 μm or more and 1,000 μm or less, more preferably 60 μm or more and 500 μm or less. By making the average thickness of the negative electrode active material layer 6 at or above the aforementioned lower limit, an energy storage element 10 with high energy density can be obtained. By making the average thickness of the negative electrode active material layer 6 at or below the aforementioned upper limit, miniaturization of the energy storage element 10 can be achieved.

[0140] (Isolation layer)

[0141] The isolation layer 3 contains a solid electrolyte. Examples of solid electrolytes include a sulfide solid electrolyte according to one embodiment of the present invention and the solid electrolyte exemplified in the description of the positive electrode for a storage element according to one embodiment of the present invention. The content of the solid electrolyte in the isolation layer 3 is preferably 70% by mass or more, more preferably 90% by mass or more, further preferably 99% by mass or more, and sometimes even more preferably substantially 100% by mass. When the isolation layer 3 uses a sulfide solid electrolyte according to one embodiment of the present invention, the content of the sulfide solid electrolyte according to one embodiment of the present invention relative to the total solid electrolyte in the isolation layer 3 is preferably 50% by mass or more, more preferably 70% by mass or more, further preferably 90% by mass or more, and even more preferably substantially 100% by mass.

[0142] The insulating layer 3 may contain any components such as phosphoric acid compounds like Li3PO4, oxides, halogen compounds, binders, thickeners, and fillers. The binders, thickeners, fillers, and other components may be selected from the materials exemplified in the positive electrode of the energy storage element according to one embodiment of the present invention.

[0143] The average thickness of the insulating layer 3 is preferably 1 μm or more and 50 μm or less, more preferably 3 μm or more and 20 μm or less. By setting the average thickness of the insulating layer 3 to the lower limit or above, the positive electrode 1 and the negative electrode 2 can be reliably insulated. By setting the average thickness of the insulating layer 3 to the upper limit or below, the energy density of the energy storage element 10 can be improved.

[0144] <Electronic Storage Devices>

[0145] The energy storage element of this embodiment can be mounted as an energy storage unit (battery module) composed of multiple energy storage elements in vehicles such as electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs), as well as in electronic devices such as personal computers and communication terminals, or as a power source for energy storage. In this case, the technology of the present invention only needs to be applied to at least one energy storage element included in the energy storage unit.

[0146] Figure 2This illustrates an example of an energy storage device 30 that further incorporates energy storage units 20, which are composed of two or more electrically connected energy storage elements 10. The energy storage device 30 may also include a busbar (not shown) electrically connecting two or more energy storage elements 10, or a busbar (not shown) electrically connecting two or more energy storage units 20. The energy storage unit 20 or the energy storage device 30 may also include a status monitoring device (not shown) for monitoring the status of one or more energy storage elements 10.

[0147] <Manufacturing Methods of Energy Storage Components>

[0148] The method for manufacturing an energy storage element according to one embodiment of the present invention can be carried out by generally known methods, except that it uses the sulfide solid electrolyte of one embodiment of the present invention as part or all of the solid electrolyte. Specifically, the manufacturing method includes, for example, a step of preparing a positive electrode mixture, a step of preparing a material for an insulating layer, a step of preparing a negative electrode mixture, and a step of stacking a positive electrode, an insulating layer, and a negative electrode. Hereinafter, each step will be described in detail.

[0149] (1) Preparation process of positive electrode mixture

[0150] In this process, a positive electrode mixture is typically prepared to form the positive electrode (positive electrode active material layer). There are no particular limitations on the method for preparing the positive electrode mixture, and it can be appropriately selected depending on the purpose. For example, the positive electrode mixture can be prepared by mixing the positive electrode active material and a solid electrolyte using methods such as mechanical grinding. Alternatively, a mixture or composite of the positive electrode active material and the solid electrolyte can be pre-prepared using the methods described above, and then the resulting mixture or composite can be mixed with other components.

[0151] (2) Preparation process of materials for the isolation layer

[0152] In this process, a material for forming the separator layer is typically prepared. In the case of an all-solid-state battery, the separator layer material can be a solid electrolyte. The solid electrolyte used as the separator layer material can be prepared using conventionally known methods. For example, it can be obtained by mechanically grinding a predetermined material. Alternatively, the separator layer material can be prepared by heating the predetermined material to above its melting temperature, melting and mixing the two materials in a predetermined ratio, and then rapidly cooling them. Other methods for synthesizing separator layer materials include, for example, a solid-phase method involving depressurization and sintering, a liquid-phase method such as dissolution and precipitation, a gas-phase method, and sintering under an argon atmosphere after mechanical grinding.

[0153] (3) Negative electrode preparation process

[0154] In this process, a negative electrode additive is typically prepared to form the negative electrode (negative electrode active material layer). The specific preparation method for the negative electrode additive is the same as that for the positive electrode additive. Alternatively, lithium foil or similar materials can be used to form the negative electrode active material layer instead of the negative electrode additive.

[0155] (4) Lamination process

[0156] In this process, for example, a positive electrode having a positive electrode substrate and a positive electrode active material layer, an isolation layer, and a negative electrode having a negative electrode substrate and a negative electrode active material layer are stacked. In this process, the positive electrode, isolation layer, and negative electrode can be formed sequentially, or vice versa; the order of formation of each layer is not particularly limited. The positive electrode is formed, for example, by press molding a positive electrode substrate and a positive electrode agent; the isolation layer is formed by press molding an isolation layer material; and the negative electrode is formed by press molding a negative electrode substrate and a negative electrode agent. Alternatively, the positive electrode substrate, positive electrode agent, isolation layer material, negative electrode agent, and negative electrode substrate can be stacked by press molding them all at once. The positive and negative electrodes can also be pre-formed separately and then stacked with the isolation layer by press molding. Each layer can also be formed by coating or the like.

[0157] <Other Implementation Methods>

[0158] It should be noted that the sulfide solid electrolyte, the method for manufacturing the sulfide solid electrolyte, the positive electrode for the energy storage element, and the energy storage element of the present invention are not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, the configuration of other embodiments can be added to the configuration of a certain embodiment; in addition, a part of the configuration of a certain embodiment can be replaced with the configuration of other embodiments or known technology. Furthermore, a part of the configuration of a certain embodiment can be deleted. In addition, known technology can be added to the configuration of a certain embodiment.

[0159] For example, the energy storage element of the present invention may also include layers other than the positive electrode, the insulating layer, and the negative electrode. The present invention can also be applied to energy storage elements having bipolar electrodes. Furthermore, the energy storage element of the present invention may also contain a liquid. Examples of such energy storage elements include those in which the gaps between the positive electrode active material layer 5, the insulating layer 3, and the negative electrode active material layer 6 in the above-described energy storage element 10 are filled with a non-aqueous electrolyte containing an ionic liquid. In addition to being used as a secondary battery, the energy storage element of the present invention can also be a capacitor.

[0160] <Example>

[0161] The present invention will be described in more detail below through embodiments, but the present invention is not limited to the following embodiments.

[0162] [Example 1]

[0163] The following process synthesizes Li 3.67 PAl 0.03 S 3.95 N 0.06 Br 0.40 I 0.27 This refers to a sulfide solid electrolyte.

[0164] Li₃N and AlN were weighed in a molar ratio of 1.2:1, mixed in a mortar, and then granulated. Next, the mixture was heat-treated at 750°C for 1 hour to prepare Li₃N. 1.5 Al 0.5 N. The Li produced 1.5 Al 0.5 X-ray diffraction analysis confirmed that the main phase was Li. 1.5 Al 0.5 N.

[0165] In a glove box with an argon atmosphere at a dew point below -50°C, Li₂S (99.98%, Aldrich), P₂S₅ (99%, Aldrich), and Li₂S₅ were subjected to... 1.5 Al 0.5 N, LiBr (99.999%, Aldrich) and LiI (99.999%, Aldrich) were weighed in a molar ratio of 54.1:18.6:2.3:15.0:10.0 and mixed in a mortar to prepare a composition containing lithium (element A), phosphorus (element A), bromine and iodine (element B and C) (halogen elements), nitrogen (element M), aluminum (element M), and sulfur.

[0166] The above composition was placed into a sealed 80 mL zirconia jar containing 160 g of zirconia balls with a diameter of 4 mm. The mixture was mechanically ground using a planetary ball mill (FRITSCH, Premium line PL-7) at a revolution speed of 510 rpm for 45 hours to obtain an intermediate.

[0167] The above intermediate was heated at 220°C for 2 hours (heat treatment) to obtain the sulfide solid electrolyte of Example 1. This heating temperature was set near the crystallization temperature, i.e., within ±50°C of the crystallization temperature. The crystallization temperature was determined by taking a portion of the mechanically ground intermediate and performing DSC analysis. The DSC analysis was performed under the following conditions: using a DSC apparatus (Rigaku, Thermo Plus DSC 8230), a sealed SUS container, and heating from room temperature to 400°C at a rate of 10°C / min.

[0168] [Examples 2, 4, 5; Comparative Examples 1, 3-8]

[0169] The amounts of raw material compounds were adjusted according to the elemental ratios and composition formulas of the sulfide solid electrolytes as shown in Table 1, and the heating temperature (HT) was set as shown in Table 1. Otherwise, the same procedure as in Example 1 was followed to obtain the sulfide solid electrolytes of Examples 2, 4, 5 and Comparative Examples 1, 3-8. Each heating temperature was within ±50°C of the crystallization temperature determined in the same manner as in Example 1.

[0170] [Example 3]

[0171] The following process synthesizes Li 3.67 PB 0.02 S 3.97 N 0.04 Br 0.40 I 0.27 This refers to a sulfide solid electrolyte.

[0172] Li₃N and BN were weighed in a molar ratio of 1.1:1, mixed in a mortar, and then granulated. Next, a heat treatment was performed at 800°C for 10 minutes to prepare Li₃N. 1.5 B 0.5 N. The Li produced 1.5 B 0.5 X-ray diffraction analysis confirmed that the main phase was Li. 1.5 B 0.5 N.

[0173] In a glove box with an argon atmosphere at a dew point below -50°C, Li₂S (99.98%, Aldrich), P₂S₅ (99%, Aldrich), and Li₂S₅ were subjected to... 1.5 B 0.5 N, LiBr (99.999%, Aldrich) and LiI (99.999%, Aldrich) were weighed in a molar ratio of 54.8:18.7:1.5:15.0:10.0 and mixed in a mortar to prepare a composition containing lithium (as element A), phosphorus (as halogen elements), bromine and iodine (as halogen elements), nitrogen (as element M), boron (as element M), and sulfur.

[0174] The above composition was placed into a sealed 80 mL zirconia jar containing 160 g of zirconia balls with a diameter of 4 mm. The mixture was mechanically ground using a planetary ball mill (FRITSCH, Premium line PL-7) at a revolution speed of 510 rpm for 45 hours to obtain an intermediate.

[0175] The above intermediate was heated at 180°C for 2 hours (heat treatment) to obtain the sulfide solid electrolyte of Example 3. This heating temperature is within ±50°C of the crystallization temperature determined in the same manner as in Example 1.

[0176] [Comparative Example 2]

[0177] The following process synthesizes Li 3.67 PSi 0.01 S 3.97 N 0.04 Br 0.40 I 0.27 This refers to a sulfide solid electrolyte.

[0178] Li3N and Si3N4 were weighed at a molar ratio of 5.1:1, mixed in a mortar, and then granulated. Next, a heat treatment was performed at 800℃ for 10 minutes to prepare Li... 1.67 Si 0.33 N. Li made 1.67 Si 0.33 X-ray diffraction analysis confirmed that the main phase was Li. 1.67 Si 0.33 N.

[0179] In a glove box with an argon atmosphere at a dew point below -50°C, Li₂S (99.98%, Aldrich), P₂S₅ (99%, Aldrich), and Li₂S₅ were subjected to... 1.67 Si 0.33 N, LiBr (99.999%, Aldrich) and LiI (99.999%, Aldrich) were weighed in a molar ratio of 54.8:18.7:1.5:15.0:10.0 and mixed in a mortar to prepare a composition containing lithium (as element A), phosphorus, bromine and iodine (as halogen elements), nitrogen, silicon and sulfur.

[0180] The above composition was placed into a sealed 80 mL zirconia jar containing 160 g of zirconia balls with a diameter of 4 mm. The mixture was mechanically ground using a planetary ball mill (FRITSCH, Premium line PL-7) at a revolution speed of 510 rpm for 45 hours to obtain an intermediate.

[0181] The above intermediate was heated at 180°C for 2 hours (heat treatment) to obtain the sulfide solid electrolyte of Comparative Example 2. This heating temperature is within ±50°C of the crystallization temperature determined in the same manner as in Example 1 above.

[0182] [Confirmation of crystal structure]

[0183] Powder X-ray diffraction (PXRD) measurements were performed on the sulfide solid electrolytes of Examples 1-5 and Comparative Examples 1-8 using the methods described above. It should be noted that the gas-tight X-ray diffraction sample holder used was manufactured by Rigaku Corporation, trade name "General Atmosphere Isolator". In the X-ray diffraction patterns of the sulfide solid electrolytes of the Examples and Comparative Examples, diffraction peaks were observed in the ranges of 2θ = 19.9° ± 0.5° and 2θ = 29.3° ± 0.5° from HICP, confirming the presence of a crystalline structure.

[0184] [Determination of Ion Conductivity]

[0185] The AC impedance was measured using a Bio-Logic VMP-300 microscope according to the above method, and the ionic conductivity (σ) of each sulfide solid electrolyte in Examples 1, 2, 4, 5 and Comparative Examples 1, 3-8 at 25°C was determined. 25 The measurement results are shown in Table 1.

[0186] [Determination of hydrogen sulfide production]

[0187] For each sulfide solid electrolyte of Example 1 and Comparative Examples 4 and 5, the amount of hydrogen sulfide (H2S) produced was determined according to the following steps. A desiccator was placed in a drying oven with a dry air atmosphere at a dew point of -35°C. Then, the solid electrolyte powder (500 mg) was placed in a sealed desiccator (actual volume 2300 cm³). 3 The internal configuration was set for 1 hour, and the amount of hydrogen sulfide produced was measured using a hydrogen sulfide sensor (PGM-1860). The measurement results are shown in Table 1.

[0188] [Evaluation of Oxidation Resistance]

[0189] The following test batteries were prepared using the sulfide solid electrolytes of Examples 1-5 and Comparative Examples 1-8, and their oxidation resistance was evaluated by square wave voltammetry (SWV).

[0190] Under an argon atmosphere with a dew point below -50°C, 80 mg of sample powder (the solid electrolyte being tested) was added to a powder forming apparatus with an inner diameter of 10 mm, and then uniaxially pressurized at a pressure below 50 MPa using a hydraulic press. After pressure release, graphite powder was added to the upper surface of the sample, and uniaxial pressing was performed again at 360 MPa for 5 minutes using a hydraulic press. Next, a metal foil obtained by bonding a lithium foil to an indium foil was placed on the lower surface of the sample, and then uniaxial pressing was performed at a pressure below 50 MPa to obtain a granular test cell. SWV was measured under the following test conditions while the test cell was pressed with a clamp at a torque of 50 cNm.

[0191] (SWV measurement conditions)

[0192] Voltage amplitude: 20mV

[0193] Relaxation time: 50ms

[0194] Step voltage: 1mV

[0195] Voltage range: OCV to 4.5V

[0196] Measurement temperature: 50℃

[0197] The measured peak current I MAX As shown in Table 1. At the peak current I... MAX If the size decreases, it can be interpreted as an improvement in oxidation resistance.

[0198] [Making of Energy Storage Components]

[0199] Using the sulfide solid electrolytes of Example 1 and Comparative Examples 4 and 5, energy storage elements were fabricated according to the following steps.

[0200] Positive electrode active material used in LiNi 0.5 Co 0.2 Mn 0.3 The surface of O2 particles is coated with LiNbO3. The above-mentioned positive electrode active material, each sulfide solid electrolyte, and fibrous carbon as a conductive agent are weighed at a predetermined mass ratio. Next, a binder (SBR) and butyl butyrate as a solvent are added to the mixture at a solid content ratio of 60% by mass, and the mixture is kneaded using a mixer to obtain the positive electrode mixture. A YBA type BAKER coater is used on an aluminum foil (average thickness 20 μm) serving as the positive electrode substrate to achieve a surface area weight of 15 mg·cm³. -2 Above and 25 mg·cm -2 The obtained positive electrode mixture was coated as follows: It was dried in an argon atmosphere dryer at a solvent evaporation temperature set to 100°C for 20 minutes under normal pressure, followed by drying under reduced pressure for 15 minutes, thereby forming a positive electrode active material layer on the positive electrode substrate. This was then stamped into a 10mm diameter circle for evaluation purposes.

[0201] A solid-state battery was fabricated using the aforementioned positive electrode. In a powder forming apparatus with an inner diameter of 10 mm, 80 mg of a sulfide solid electrolyte of the silver-germanium sulfide type, represented by Li6PS5Cl, was added as the separator material. The mixture was then pressurized at 100 MPa for several seconds at room temperature using uniaxial pressing to form the separator layer. After pressure release, the fabricated positive electrode was placed onto one side of the separator layer and pressurized at 160°C and 400 MPa for 5 minutes using uniaxial pressing. After pressure release, on the side of the positive electrode opposite to the bonding surface, indium foil and lithium foil as the negative electrode, and SUS316L foil as the negative electrode substrate, were added and bonded at 50 MPa for several seconds at room temperature using uniaxial pressing. The mixture was then removed from the ceramic powder forming apparatus, thus obtaining the energy storage element (solid-state battery).

[0202] [Charge / Discharge Test]

[0203] For each obtained energy storage element, charge and discharge tests were conducted at 50°C according to the following procedure: Constant current and constant voltage charging was performed at a current of 0.1C with a charging termination voltage of 3.75V. The charging was terminated when the current reached 0.025C. Then, a 10-minute pause was set. Next, constant current discharging was performed at a current of 0.1C with a discharging termination voltage of 2.25V. The ratio of the discharge capacity to the initial charge capacity was calculated as the initial charge-discharge efficiency.

[0204] Next, for each energy storage element, a charge-discharge cycle test was conducted at 50°C according to the following procedure: Constant current and constant voltage charging was performed at a current of 0.2C with a charging termination voltage of 3.75V. The charging was terminated when the current reached 0.05C. Then, a 10-minute pause was set. Next, constant current discharging was performed at a current of 0.2C with a discharging termination voltage of 2.25V. Then, a 10-minute pause was set. This charge-discharge cycle was performed for 30 cycles. The ratio of the discharge capacity of the 30th cycle to the discharge capacity of the 1st cycle was calculated as the capacity retention rate.

[0205] The results of the initial charge / discharge efficiency and capacity retention are shown in Table 1.

[0206] [Table 1]

[0207]

[0208] As shown in Table 1, in Comparative Examples 1, 2, 5, and 6 (which do not contain nitrogen or element M), Comparative Examples 3 and 4 (where the molar ratio of nitrogen to phosphorus content (N / P) is 0.33 or higher), and Comparative Examples 7 and 8 (where the molar ratio of lithium (element A) to phosphorus content (A / P) is 3.74 or higher), the peak current I... MAXIts value is above 11.2, indicating low oxidation resistance.

[0209] In contrast, in the sulfide solid electrolytes of Examples 1-5, which contain nitrogen and element M, have a nitrogen content to phosphorus content molar ratio (N / P) of less than 0.33 and a lithium content (element A) to phosphorus content molar ratio (A / P) of less than 3.74, the peak current I, as an indicator of oxidation resistance, is... MAX The value is less than 11.2, indicating high oxidation resistance. Furthermore, the energy storage element using the sulfide solid electrolyte of Example 1, which exhibits high oxidation resistance, demonstrates higher initial charge / discharge efficiency and capacity retention compared to the energy storage elements using the sulfide solid electrolytes of Comparative Examples 4 and 5, which have low oxidation resistance.

[0210] Industrial availability

[0211] The sulfide solid electrolyte of the present invention is suitable for use as a solid electrolyte in energy storage devices such as all-solid-state batteries.

[0212] Explanation of reference numerals in the attached figures

[0213] 1: Positive electrode, 2: Negative electrode, 3: Separator layer, 4: Positive electrode substrate, 5: Positive electrode active material layer, 6: Negative electrode active material layer, 7: Negative electrode substrate, 10: Energy storage element (all-solid-state battery), 20: Energy storage unit, 30: Energy storage device.

Claims

1. A sulfide solid electrolyte having a crystalline structure and containing at least one element A selected from the group consisting of lithium, sodium, and potassium, phosphorus, at least one element M selected from the group consisting of aluminum and boron, nitrogen, and at least one halogen element. The molar ratio of element A to phosphorus, i.e., A / P, is less than 3.

74. The molar ratio of nitrogen content to phosphorus content, i.e., N / P, is less than 0.

33.

2. The sulfide solid electrolyte according to claim 1, wherein, The element M contains aluminum.

3. The sulfide solid electrolyte according to claim 1 or 2, wherein, The halogen element includes bromine or iodine.

4. The sulfide solid electrolyte according to claim 1 or 2, which is represented by the following formula (1), TO a P.M b S c N d X e AND f ···(1) In the above formula (1), A is at least one selected from the group consisting of Li, Na and K, M is at least one selected from the group consisting of Al and B, X is at least one selected from the group consisting of F, Cl, Br and I, Y is at least one element other than A, P, S, M, N and X, and a, b, c, d, e and f satisfy 2≤a<3.74, 0.01≤b≤1, 2≤c≤6, 0.01≤d<0.33, 0.01≤e≤1 and 0≤f≤1 respectively.

5. A method for manufacturing a sulfide solid electrolyte, comprising a step of processing a composition, The composition contains at least one element A selected from the group consisting of lithium, sodium and potassium, phosphorus, at least one element M selected from the group consisting of aluminum and boron, nitrogen, and at least one halogen element, wherein the molar ratio of element A to phosphorus (A / P) is less than 3.74, and the molar ratio of nitrogen to phosphorus (N / P) is less than 0.

33.

6. The method for manufacturing a sulfide solid electrolyte according to claim 5, wherein, The composition contains A α M β The compound represented by N, where A is element A, M is element M, and α and β are stoichiometric values ​​assigned according to the type of element M.

7. A sulfide solid electrolyte, which is manufactured by the method for manufacturing a sulfide solid electrolyte according to claim 5 or 6.

8. A positive electrode for an energy storage element, comprising a sulfide solid electrolyte as described in claim 1 or 2.

9. An energy storage element comprising a sulfide solid electrolyte as described in claim 1 or 2.

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