Solid electrolyte, method for producing solid electrolyte, and electric storage device

Abstract

To provide a solid electrolyte exhibiting high water resistance, a method for producing such a solid electrolyte, and an electric storage device employing such a solid electrolyte.SOLUTION: A solid electrolyte contains, as constituent elements, lithium, phosphorus, sulfur, a halogen, and tin, wherein the content of the tin relative to the content of the phosphorus is 0.2 or less in a molar ratio, and the solid electrolyte has a crystalline structure. An electric storage device 10 is an all-solid-state battery and is a secondary battery in which a positive electrode layer 1 and a negative electrode layer 2 are arranged with a separation layer 3 interposed therebetween. The positive electrode layer 1 includes a positive electrode base material 4 and a positive electrode active material layer 5, and the positive electrode base material 4 constitutes an outermost layer of the positive electrode layer 1. The negative electrode layer 2 includes a negative electrode base material 7 and a negative electrode active material layer 6, and the negative electrode base material 7 constitutes an outermost layer of the negative electrode layer 2.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a solid electrolyte, a method for producing the solid electrolyte, and an electric storage element. [Background technology]

[0002] Due to their high energy density, lithium ion secondary batteries are widely used in electronic devices such as personal computers and communication terminals, automobiles, etc. The lithium ion secondary batteries generally have a pair of electrodes electrically isolated by a separator and a non-aqueous electrolyte interposed between the electrodes, and are configured to charge and discharge by transferring lithium ions between the electrodes. Furthermore, capacitors such as lithium ion capacitors are also widely used as energy storage elements other than lithium ion secondary batteries.

[0003] In recent years, energy storage devices have been proposed that use solid electrolytes such as sulfide solid electrolytes as non-aqueous electrolytes instead of non-aqueous electrolyte solutions in which an electrolyte salt is dissolved in a liquid such as an organic solvent. Patent Document 1 describes one sulfide solid electrolyte material that contains Li, A (A is at least one of P, Si, Ge, Al, and B), X (X is a halogen), and S, is a glass ceramic, and exhibits peaks at 2θ = 20.2° and 23.6° in X-ray diffraction measurement using CuKα radiation. Patent Document 2 also describes the production of a sulfide solid electrolyte having a composition of xLiS-25P2S5-yLi3N using Li2S, P2S5, and Li3N as starting materials. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-016423 [Patent Document 2] Japanese Patent Application Publication No. 2018-041671 Summary of the Invention [Problem to be solved by the invention]

[0005] Sulfide solid electrolytes have the disadvantage of reacting with water in the atmosphere due to their low water resistance. Therefore, even when the sulfide solid electrolyte is left in a dry air atmosphere with a low moisture content, the ionic conductivity decreases due to the reaction with water, and even when the sulfide solid electrolyte is subsequently dried, the ionic conductivity does not fully recover. Here, Patent Document 2 discloses that the water resistance of a sulfide solid electrolyte can be improved by including nitrogen in the sulfide solid electrolyte. However, when LiN is used as a raw material for such a sulfide solid electrolyte, nitrogen is easily discharged outside the system during heat treatment, and the water resistance cannot be sufficiently improved.

[0006] The present invention has been made in light of the above circumstances, and an object of the present invention is to provide a solid electrolyte having high water resistance, a method for producing such a solid electrolyte, and an energy storage element using such a solid electrolyte. [Means for solving the problem]

[0007] One aspect of the present invention, which has been made to solve the above problems, is a solid electrolyte having a crystalline structure and containing lithium, phosphorus, sulfur, a halogen, and tin as constituent elements.

[0008] Another aspect of the present invention is a method for producing a solid electrolyte, comprising: preparing a composition containing lithium, phosphorus, sulfur, a halogen, and tin; reacting the composition to obtain an intermediate; and heating the intermediate.

[0009] Another embodiment of the present invention is an energy storage element including the solid electrolyte according to one embodiment of the present invention. [Effects of the Invention]

[0010] According to one embodiment of the present invention, it is possible to provide a solid electrolyte having high water resistance, a method for manufacturing such a solid electrolyte, and an energy storage element using such a solid electrolyte. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic cross-sectional view of an all-solid-state battery, which is one embodiment of the energy storage element of the present invention. [Figure 2] FIG. 2 is a schematic diagram showing an energy storage device configured by assembling a plurality of energy storage elements according to one embodiment of the present invention. [Figure 3] FIG. 3 is an X-ray diffraction diagram of each of the solid electrolytes of Examples 1, 3, 3′, and 5 and Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0012] First, an outline of the solid electrolyte, the method for producing the solid electrolyte, and the energy storage element disclosed in this specification will be described.

[0013] A solid electrolyte according to one embodiment of the present invention is a solid electrolyte containing lithium, phosphorus, sulfur, a halogen, and tin as constituent elements and having a crystalline structure.

[0014] The solid electrolyte has high water resistance. Therefore, the ionic conductivity of the solid electrolyte is less likely to decrease when left in a dry air atmosphere, and the recovery rate of the ionic conductivity when dried thereafter is also high. The reason why the solid electrolyte exhibits such effects is not clear, but the following reasons are presumed. The solid electrolyte further contains tin in addition to conventional sulfide solid electrolytes that contain lithium, phosphorus, sulfur, and halogens and have a crystalline structure. According to the HSAB (Hard and Soft Acids and Bases) rule, hard anions (O 2- ) is a hard cation (P 5+ ), which is a soft cation. Therefore, in conventional sulfide solid electrolytes, reactions between water molecules in the atmosphere and phosphorus in the sulfide solid electrolyte tend to occur. In contrast, the solid electrolyte according to one embodiment of the present invention is characterized by its ability to bond with tin (Sn 4+ ) reduces the areas that are easily bonded with oxygen, which is thought to result in increased water resistance.

[0015] The presence of a crystalline structure can be confirmed by powder X-ray diffraction measurement. Specifically, "having a crystalline structure" means that peaks attributable to the crystalline structure of the solid electrolyte are observed in the X-ray diffraction pattern in powder X-ray diffraction measurement. The solid electrolyte may contain amorphous portions. Powder X-ray diffraction measurement is performed as follows: A gastight sample holder for X-ray diffraction measurement is filled with the solid electrolyte powder to be measured under an argon atmosphere with a dew point of -50°C or less. Powder X-ray diffraction measurement is performed using an X-ray diffractometer (MiniFlex II, manufactured by Rigaku). The radiation source is CuKα radiation, the tube voltage is 30 kV, and the tube current is 15 mA. The diffracted X-rays are passed through a 30 μm-thick Kβ filter and detected by a high-speed one-dimensional detector (model number: D / teX Ultra 2). The sampling width is 0.01°, the scan speed is 5° / min, the divergence slit width is 0.625°, the receiving slit width is 13 mm (OPEN), and the scattering slit width is 8 mm.

[0016] The crystalline structure of the solid electrolyte preferably has diffraction peaks in the range of 20.2°±0.5° and 23.6°±0.5° in an X-ray diffraction diagram using CuKα radiation. HICP (High Ion Conduction Phase), a highly Li-ion conductive crystalline phase, has diffraction peaks in the range of 20.2°±0.5° and 23.6°±0.5° in an X-ray diffraction diagram using CuKα radiation. Therefore, when such diffraction peaks appear in the solid electrolyte, it can be said that HICP is sufficiently formed, and high ionic conductivity can be exhibited. The "X-ray diffraction diagram using CuKα radiation" is obtained by the powder X-ray diffraction measurement described above.

[0017] The crystalline structure of the solid electrolyte preferably has a diffraction peak in the range of 25.6°±0.5° in an X-ray diffraction pattern using CuKα radiation. 4 / 3 Sn 1 / 3 S 4 / 3The (LSS) phase has a diffraction peak in the range of 25.6°±0.5° in an X-ray diffraction diagram using CuKα radiation. Therefore, when such a diffraction peak appears in the solid electrolyte, it can be said that the LSS phase is sufficiently formed, and water resistance tends to be improved. Furthermore, the ionic conductivity of LSS is higher in a glass-ceramic state having a crystalline structure than in an amorphous state (glass state). Therefore, in the solid electrolyte, even if it has the same elemental composition, if it has a diffraction peak in the range of 25.6°±0.5° in an X-ray diffraction diagram using CuKα radiation, the ionic conductivity tends to be higher.

[0018] In the solid electrolyte, the molar ratio of the tin content to the phosphorus content is preferably 0.05 to 1.0. When the tin content is within the above range, both water resistance and ionic conductivity can be improved in a balanced manner.

[0019] The solid electrolyte further contains nitrogen and an element M as constituent elements, and the element M is preferably at least one element selected from the group consisting of aluminum, tantalum, silicon, scandium, magnesium, niobium, boron, hafnium, carbon, zirconium, and titanium.

[0020] In the case of such a solid electrolyte, the discharge of nitrogen, an element that enhances the water resistance as described above, out of the system is suppressed during the manufacturing process of the solid electrolyte, thereby further enhancing water resistance. The reason for this is not clear, but the following reason is presumed. In the manufacturing method of a sulfide solid electrolyte using Li3N disclosed in Patent Document 2, the nitrogen defect formation energy of Li3N is small, and nitrogen gas is easily generated. In contrast, when a raw material compound containing nitrogen and element M is used, the nitrogen defect formation energy is large, and nitrogen defects are unlikely to be generated during the synthesis process, and therefore nitrogen gas is unlikely to be generated. Therefore, the discharge of nitrogen out of the system during the manufacturing process can be suppressed. Note that element M is either A, calculated by first-principles calculations described below. α M βN (A is at least one element selected from the group consisting of lithium, sodium, and potassium; M is the element M; α and β are values ​​that give a stoichiometric ratio depending on the type of element M) is an element having a nitrogen defect formation energy of 4.00 eV or more. The definition of the nitrogen defect formation energy will be described later.

[0021] The solid electrolyte preferably contains at least one halogen selected from bromine and iodine, which can further increase the ionic conductivity of the solid electrolyte.

[0022] A method for producing a solid electrolyte according to one embodiment of the present invention includes preparing a composition containing lithium, phosphorus, sulfur, a halogen, and tin, reacting the composition to obtain an intermediate, and heating the intermediate.

[0023] According to this manufacturing method, a solid electrolyte having high water resistance can be manufactured.

[0024] The term "composition" refers to a mixture of two or more compounds or simple substances (hereinafter, compounds and simple substances are collectively referred to as "compounds, etc."). The entire composition, i.e., any compound, etc. contained in the composition may contain lithium, phosphorus, sulfur, halogen, and tin.

[0025] The composition preferably contains a compound containing lithium, sulfur, and tin. A solid electrolyte having higher water resistance and ionic conductivity can be produced by preparing or synthesizing such a compound in advance, reacting a composition containing this compound to obtain an intermediate, and heating this intermediate.

[0026] An electric storage element according to one embodiment of the present invention is an electric storage element containing the solid electrolyte. Because the electric storage element uses a highly water-resistant solid electrolyte, even if the solid electrolyte is temporarily placed in an atmospheric environment during the manufacturing process, the reaction of the solid electrolyte with water is suppressed, and the electric storage element exhibits good performance.

[0027] A solid electrolyte, a method for producing the solid electrolyte, and an energy storage device according to one embodiment of the present invention will be described in detail below.

[0028] <Solid electrolyte> (composition) A solid electrolyte according to one embodiment of the present invention contains lithium, phosphorus, sulfur, a halogen, and tin as constituent elements. Examples of the halogen include chlorine, bromine, and iodine, with bromine and iodine being preferred. When the halogen contains at least one selected from bromine and iodine, the ionic conductivity of the solid electrolyte can be further improved. One or more halogens may be contained.

[0029] In one embodiment of the present invention, the ratio of the tin content to the phosphorus content (Sn / P) may be, for example, 0.01 or more and 2 or less in molar ratio, but may be preferably 0.05 or more and 1.0 or less, more preferably 0.1 or more and 0.6 or less, and even more preferably 0.4 or less, 0.2 or less, or 0.15 or less. By setting the content ratio (Sn / P) to the above-mentioned lower limit or more, it is possible to incorporate a sufficient amount of tin into the solid electrolyte, thereby further improving water resistance. On the other hand, by setting the content ratio (Sn / P) to the above-mentioned upper limit or less, ionic conductivity tends to be increased.

[0030] The ratio of the lithium content to the phosphorus content (Li / P) is preferably 3 or more and 10 or less, more preferably 3.4 or more and 8 or less, even more preferably 3.8 or more and 6 or less, and in some cases even more preferably 5 or less or 4.5 or less. By setting the content ratio (Li / P) within the above range, the composition of the solid electrolyte is more optimized, and the water resistance, ionic conductivity, etc. are further improved.

[0031] The ratio of the sulfur content to the phosphorus content (S / P) is preferably 2 or more and 10 or less, more preferably 3 or more and 8 or less, even more preferably 3.5 or more and 6 or less, and in some cases even more preferably 5 or less. By setting the content ratio (S / P) within the above range, the composition of the solid electrolyte is more optimized, and the water resistance, ionic conductivity, etc. are further improved.

[0032] The ratio (X / P) of the halogen (X) content to the phosphorus content is preferably 0.1 or more and 1 or less, more preferably 0.2 or more and 0.8 or less, and even more preferably 0.3 or more and 0.6 or less, in terms of molar ratio. By setting the content ratio (X / P) to the above lower limit or more, HICPs may be more likely to precipitate, and ionic conductivity may be increased. On the other hand, by setting the content ratio (X / P) to the above upper limit or less, a lithium halide crystalline phase may be less likely to remain, and ionic conductivity may be increased.

[0033] The solid electrolyte further contains nitrogen and element M as constituent elements, and the element M is preferably at least one selected from the group consisting of aluminum, tantalum, silicon, scandium, magnesium, niobium, boron, hafnium, carbon, zirconium, and titanium. The element M is more preferably at least one selected from the group consisting of aluminum, tantalum, silicon, scandium, magnesium, niobium, and boron. When the solid electrolyte further contains such an element, its water resistance is further improved.

[0034] The ratio (N / P) of the nitrogen (N) content to the phosphorus content is preferably 0.01 or more and 1.2 or less, more preferably 0.1 or more and 1.0 or less, and even more preferably 0.2 or more and 0.6 or less, in molar ratio. By setting the content ratio (N / P) to the above lower limit or more, water resistance can be further improved. On the other hand, by setting the content ratio (N / P) to the above upper limit or less, ionic conductivity and the like are improved.

[0035] The ratio of the content of element M to the content of phosphorus (M / P) is preferably 0.01 to 1 in molar ratio, more preferably 0.05 to 0.6 in molar ratio, and even more preferably 0.1 to 0.4 in molar ratio. By setting the content ratio (M / P) to the above lower limit or more, the discharge of nitrogen to the outside of the system can be more sufficiently suppressed, and water resistance can be further improved. On the other hand, by setting the content ratio (M / P) to the above upper limit or less, ionic conductivity and the like can be further improved.

[0036] The ratio of the content of element M to the content of nitrogen (M / N) is preferably 0.1 or more and 2 or less, more preferably 0.3 or more and 1 or less, in molar ratio, by which the ratio of the contents (M / N) is within the above range, thereby making it possible to further improve the water resistance, ionic conductivity, etc.

[0037] The solid electrolyte may further contain other elements other than lithium, phosphorus, sulfur, halogen, tin, nitrogen, and element M. However, the ratio of the content of the other elements to the content of phosphorus in the solid electrolyte may preferably be, for example, less than 0.1 in molar ratio, more preferably less than 0.01, and may not be substantially contained.

[0038] In one embodiment of the present invention, the solid electrolyte may be represented by the following formula 1: (100-d)((1-c)((1-b)(aLi2S·(1-a)P2S5)·bLi α M β N)·cLiX)·dLi 4 / 3 Sn 1 / 3 S 4 / 3 ·eY ···1 In the above formula 1, X is a halogen. M is the above element M. Y is one or more elements other than Li, P, S, X (halogen), N, and M (element M). a is a number of 0.5 or more and 0.8 or less. b is a number of more than 0 and 0.5 or less. c is a number of 0.04 or more and 0.4 or less. d is a number of more than 0 and 60 or less. e is a number of 0 or more and 25 or less.

[0039] The above formula 1 indicates the content ratio of each element Li, P, S, N, M, X, and Y in the solid electrolyte (composition formula), and does not specify the raw material compound.

[0040] Specific examples and preferred examples of the above X (halogen), M (element M), etc. are as described above. The above Z and the above M may each be two or more elements.

[0041] The above-mentioned a is preferably 0.6 or more and 0.78 or less, and more preferably 0.67 or more and 0.76 or less. The above b is preferably 0.05 or more and 0.4 or less, and more preferably 0.1 or more and 0.3 or less. The above c is preferably 0.1 or more and 0.35 or less. The above d is preferably 1 or more and 50 or less, more preferably 5 or more and 40 or less, and may be even more preferably 30 or less or 20 or less. The above e may be 0 or more and 5 or less, 0 or more and 1 or less, or may be 0.

[0042] When the solid electrolyte has such a composition, the water resistance, ionic conductivity, and the like are further improved.

[0043] (crystal structure) The solid electrolyte has a crystalline structure. The crystalline structure of the solid electrolyte is HICP, LGPS type, argyrodite type, Li 4 / 3 Sn 1 / 3 S 4 / 3 (LSS), Li7P3S 11 , β-Li3PS4, Thio-LISICON, etc. Among these, the solid electrolyte preferably contains HICP as a crystalline structure, since it can exhibit high ionic conductivity. That is, the solid electrolyte preferably has diffraction peaks at diffraction angles 2θ derived from HICP in the ranges of 20.2°±0.5° and 23.6°±0.5° in an X-ray diffraction diagram using CuKα radiation.

[0044] This solid electrolyte has a crystalline structure of Li, which provides better water resistance and ionic conductivity. 4 / 3 Sn 1 / 3 S 4 / 3 It is preferable that the solid electrolyte contains a (LSS) phase. That is, it is preferable that the solid electrolyte has a diffraction peak at a diffraction angle 2θ of 25.6°±0.5° due to the LSS phase in an X-ray diffraction pattern using CuKα radiation.

[0045] (Physical properties, uses, etc.) The lower limit of the ionic conductivity of the solid electrolyte at 25°C is preferably 0.2 mS / cm, more preferably 0.5 mS / cm, even more preferably 1 mS / cm, and even more preferably 2 mS / cm. When the ionic conductivity of the solid electrolyte at 25°C is equal to or greater than the lower limit, the charge / discharge performance of the energy storage device can be improved. The upper limit of the ionic conductivity is, for example, 50 mS / cm, and may be 25 mS / cm.

[0046] The ionic conductivity of the solid electrolyte was determined by measuring AC impedance using the following method. In an argon atmosphere with a dew point of -50°C or lower, 120 mg of sample powder was placed in a powder molder with an inner diameter of 10 mm and then uniaxially pressed at 50 MPa or lower using a hydraulic press. After releasing the pressure, 120 mg of SUS316L powder was placed on the top surface of the sample as a current collector and then uniaxially pressed at 50 MPa or lower using a hydraulic press. Next, 120 mg of SUS316L powder was placed on the bottom surface of the sample as a current collector and then uniaxially pressed at 360 MPa for 5 minutes to obtain a pellet for ionic conductivity measurement. This pellet for ionic conductivity measurement was inserted into a Hohsen HS cell, and AC impedance measurement was performed at a specified temperature. The measurement conditions were an applied voltage amplitude of 20 mV, a frequency range of 1 MHz to 100 mHz, and a measurement temperature of 25°C.

[0047] The shape of the solid electrolyte is not particularly limited, and is usually granular, blocky, or the like. The solid electrolyte can be suitably used as an electrolyte for a storage element such as a lithium ion secondary battery, particularly a lithium ion storage element. In particular, it can be suitably used as an electrolyte for an all-solid-state battery. The solid electrolyte can be used in any of a positive electrode layer, a separator layer, a negative electrode layer, or the like in a storage element.

[0048] <Solid electrolyte manufacturing method> Although the method for producing a solid electrolyte according to one embodiment of the present invention is not particularly limited, the following method is preferred: That is, the method for producing a solid electrolyte according to one embodiment of the present invention includes preparing a composition containing lithium, phosphorus, sulfur, a halogen, and tin (preparation step), reacting the composition to obtain an intermediate (reaction step), and heating the intermediate (heating step).

[0049] (preparation process) In this process, a composition containing lithium, phosphorus, sulfur, a halogen, and tin is prepared. The composition is usually a mixture of two or more compounds containing at least one element selected from the group consisting of lithium, phosphorus, sulfur, a halogen, and tin. The composition (mixture) may contain the elements lithium, phosphorus, sulfur, a halogen, and tin. Two or more elements selected from the group consisting of lithium, phosphorus, sulfur, a halogen, and tin may be contained in one compound. The composition may also contain a compound containing none of the elements lithium, phosphorus, sulfur, a halogen, and tin.

[0050] Examples of the lithium-containing compound include Li2S, Li2O, Li3N, Li2CO3, LiX (X is a halogen), metallic lithium, etc. In addition, the Li-Sn-S-containing compound and the Li-MN-containing compound described below are also lithium-containing compounds. Among these, Li2S is preferred. The lithium-containing compound may be used alone or in combination of two or more.

[0051] 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. One type of phosphorus-containing compound may be used alone, or two or more types may be used in combination.

[0052] Examples of compounds containing sulfur include Li2S, P2S3, P2S5, Al2S3, SiS2, SnS2, and Li 4 / 3 Sn 1 / 3 S 4 / 3 Among these, Li2S, P2S3, P2S5, SnS2 and Li 4 / 3 Sn 1 / 3 S 4 / 3 The sulfur-containing compounds may be used alone or in combination of two or more.

[0053] Examples of compounds containing halogen include metal halides such as LiX (X is a halogen, specifically LiCl, LiBr, LiI, etc.), MgCl, MgBr, MgI, CaCl, CaBr, CaI, and tin halides (SnCl, SnI, etc.). Among these, LiX is preferred, and LiBr and LiI are more preferred. One type of compound containing halogen may be used alone, or two or more types may be used in combination.

[0054] Compounds containing tin include SnS, SnS2, SnO2, tin halides (SnCl2, SnI2, etc.), Li 4 / 3 Sn 1 / 3 S 4 / 3 The tin-containing compounds may be used singly or in combination of two or more.

[0055] (Li-Sn-S containing compound) Among the compounds containing tin, Li 4 / 3 Sn 1 / 3 S 4 / 3Compounds containing lithium, tin, and sulfur (hereinafter also referred to as Li-Sn-S-containing compounds), such as Li-Sn-S-containing compounds, can be suitably used. By subjecting a composition containing the Li-Sn-S-containing compound to a reaction step and a heating step, a solid electrolyte with higher water resistance and ion conductivity can be produced. The Li-Sn-S-containing compound used may have a crystalline structure or may be glassy.

[0056] The Li-Sn-S containing compound can be produced, for example, by preparing a lithium-containing compound, a tin-containing compound, and a sulfur-containing compound, mixing them in a mortar or the like, and then subjecting them to mechanical milling. The raw material compound can be a compound containing two of the elements lithium, tin, and sulfur. For example, by using Li2S and SnS2 and subjecting them to mechanical milling, Li 4 / 3 Sn 1 / 3 S 4 / 3 By performing mechanical milling, a glassy Li-Sn-S-containing compound can be efficiently obtained. However, the Li-Sn-S-containing compound may also be synthesized by a method other than mechanical milling.

[0057] Mechanical milling may be either dry or wet. Examples of mechanical milling include a container-driven mill, a media-agitating mill, milling using a high-speed rotary grinder, a roller mill, a jet mill, etc. Examples of container-driven mills include a rotary mill, a vibration mill, a planetary mill, etc. Examples of media-agitating mills include an attritor, a bead mill, etc. Examples of milling using a high-speed rotary grinder include a hammer mill, a pin mill, etc. Among these, a container-driven mill is preferred, and a planetary mill is particularly preferred.

[0058] (Li-MN containing compound) The composition preferably further contains nitrogen and the element M, more preferably contains a compound containing nitrogen and the element M, and A α M βIt is more preferable that the compound contains a compound represented by the formula N (A is at least one element selected from the group consisting of Li, Na, and K; M is the element M; α and β are values ​​that provide a stoichiometric ratio depending on the type of element M). Examples of such compounds include raw material compounds containing lithium, nitrogen, and element M (hereinafter also referred to as Li-MN-containing compounds). The Li-MN-containing compound can be produced by the following procedure. First, LiN and a nitride of element M are prepared and mixed in a mortar or the like. Next, pellets of the mixed raw material compounds are produced. Next, the pellets are heat-treated to produce the Li-MN-containing compound. Note that the method for preparing the Li-MN-containing compound is not limited to this, and other methods may also be used. For example, the raw materials for the Li-MN-containing compound may be two or more compounds containing any of lithium, element M, and nitrogen. The Li-MN-containing compound may be produced by mechanical milling. An industrially produced and commercially available Li-MN-containing compound may also be prepared.

[0059] As the Li-MN-containing compound, a lithium composite nitride of element M is preferably used. Examples of the lithium composite nitride of element M include Li 3 / 2 Al 1 / 2 N, Li 3 / 2 B 1 / 2 N, Li 5 / 3 Si 1 / 3 N, Li 9 / 5 Si 3 / 10 N, LiMgN, LiHf 1 / 2 N, Li 3 / 2 Sc 1 / 2 N, LiZr 1 / 2 N, Li 5 / 3 Ti 1 / 3 N, Li 4 / 3 Ta 1 / 3 N, Li 7 / 4 Ta 1 / 4 N, Li 7 / 4 Nb 1 / 4 N, LiC 1 / 2 Among these, Lithium nitrides such as LiN are the most popular because they are easily available. 3 / 2 Al 1 / 2 N, Li 3 / 2B 1 / 2 N, and Li 5 / 3 Si 1 / 3 N is preferred. From the viewpoint of suppressing the precipitation of Li2S, Li 3 / 2 Al 1 / 2 N is particularly preferred, and Li is preferred from the viewpoint of improving the thermal stability of HICP. 3 / 2 B 1 / 2 N and Li 5 / 3 Si 1 / 3 N is particularly preferred. From the viewpoint of suppressing the emission of nitrogen out of the system during the production process of the solid electrolyte, Li 3 / 2 Al 1 / 2 N and Li 3 / 2 B 1 / 2 N is particularly preferred.

[0060] The composition may contain a compound containing element M and a compound containing nitrogen. Examples of compounds containing element M include oxides of element M, sulfides of element M, nitrides of element M, and alloys of element M and lithium. Examples of sulfides of element M include Al2S3 and SiS2. Examples of nitrides of element M include AlN, Si3N4, BN, and Mg3N2. One compound containing element M may be used alone, or two or more compounds may be used in combination.

[0061] The element M in this production method is not particularly limited as long as it is at least one element selected from the group consisting of aluminum, tantalum, silicon, scandium, magnesium, niobium, boron, hafnium, carbon, zirconium, and titanium. Among these, from the viewpoint of more reliably suppressing the emission of nitrogen to the outside of the system in the production process of the solid electrolyte, the element M is preferably any one of aluminum, tantalum, silicon, scandium, magnesium, niobium, boron, hafnium, and carbon, and more preferably any one of aluminum, tantalum, silicon, scandium, magnesium, niobium, and boron. Furthermore, because of ease of availability, the element M is even more preferably any one of aluminum, silicon, and boron. In particular, the element M may be aluminum.

[0062] In addition to the Li-MN-containing compounds described above, examples of the nitrogen-containing compound include Li3N, PN, P3N5, S4N4, S2N2, and S4N2. Among these, Li3N is preferred. The nitrogen-containing compound may be used alone or in combination of two or more.

[0063] Specific forms of the composition prepared in the preparation step include the following (i) and (ii). (i) Li2S, P2S5, LiX (lithium halides) and Li 3 / 2 Al 1 / 2 Sulfide glass formed from N (an example of a Li-MN-containing compound) and Li 4 / 3 Sn 1 / 3 S 4 / 3 (An example of a Li-Sn-S-containing compound) (ii) Li2S, P2S5, LiX (lithium halides), Li 3 / 2 Al 1 / 2 N (an example of a Li-MN-containing compound) and a mixture of SnS2

[0064] The composition (mixture) of (i) above is Li 4 / 3 Sn 1 / 3 S 4 / 3 Other than Li2S, P2S5, LiX (lithium halides) and Li 3 / 2 Al 1 / 2 N (an example of a Li-Mn-containing compound) is previously made into a glassy state (sulfide glass) by mechanical milling or the like. This mechanical milling can be performed by the method described above as one of the procedures for synthesizing a Li-Sn-S-containing compound. 4 / 3 Sn 1 / 3 S 4 / 3(an example of a Li-Sn-S-containing compound) is also preferably glassy, ​​for example, by the synthesis procedure using the mechanical milling process described above. When the composition is a mixture of glassy compounds, a solid electrolyte with high ionic conductivity and less water-resistant crystalline phases such as LiS can be obtained. That is, the preparation step may be a step of preparing a composition containing a first glassy compound containing lithium, phosphorus, and a halogen, and a second glassy compound (Li-Sn-S-containing compound) containing lithium, tin, and sulfur. The first glassy compound and the second glassy compound may further contain other constituent elements.

[0065] On the other hand, the composition (mixture) of (ii) does not contain the Li-Sn-S-containing compound, but contains the compounds that are its raw materials. Furthermore, each compound contained in the composition of (ii) is not glassy in the preparation process, and is only made glassy in the subsequent reaction process. The composition of (ii) may contain a glassy compound. When the composition of (ii) is used, the synthesis procedure can be simplified, thereby increasing productivity.

[0066] The specific form of the composition prepared in the preparation step may be, for example, a composition obtained by removing the Li-MN-containing compound from the above compositions (i) and (ii), i.e., (i') Sulfide glasses formed from Li2S, P2S5, and LiX (lithium halides) and Li 4 / 3 Sn 1 / 3 S 4 / 3 (an example of a Li-Sn-S-containing compound), (ii') Mixtures of Li2S, P2S5, LiX (lithium halide), and SnS2, etc., are also included.

[0067] The specific and preferred contents of each element (lithium, phosphorus, sulfur, halogen, tin, etc.) in the composition prepared in the preparation step are the same as the specific and preferred contents of each element (lithium, phosphorus, sulfur, halogen, tin, etc.) in the solid electrolyte according to one embodiment of the present invention described above. In addition, the composition may further contain elements other than lithium, phosphorus, sulfur, halogen, tin, nitrogen, and element M.

[0068] (Reaction step) In this step, the composition is reacted by, for example, mechanical milling to obtain an intermediate. Note that the means for obtaining the intermediate is not limited to this, and other methods may be used. For example, a melt quenching method may be used instead of mechanical milling. The mechanical milling in this reaction step can be performed by the method described above as one of the procedures for synthesizing the Li-Sn-S-containing compound.

[0069] The intermediate obtained in the reaction step may have a crystalline structure, but is preferably a sulfide glass. When the intermediate is a sulfide glass, a sulfide solid electrolyte can be obtained in which each element is highly dispersed and there is little less of a less stable crystalline phase such as LiS.

[0070] (Heat treatment process) In this step, the intermediate is heated (heat treated) at a temperature equal to or higher than the crystallization temperature. This causes at least a portion of the intermediate to crystallize, preferably the HICP and Li 4 / 3 Sn 1 / 3 S 4 / 3 The resulting solid electrolyte is crystallized into a (LSS) phase, thereby obtaining the target solid electrolyte. The heating (heat treatment) may be performed under reduced pressure or in an inert gas atmosphere. The heating temperature range is, for example, preferably 160°C to 400°C, more preferably 170°C to 350°C, and even more preferably 180°C to 300°C. By setting the heating temperature to above the lower limit, crystallization progresses sufficiently, and a solid electrolyte with higher ionic conductivity can be obtained. Furthermore, by setting the heating temperature to below the upper limit, the target crystalline phase can be effectively precipitated.

[0071] (Raw material compound A α M β (How to select N) As mentioned above, A is an example of a compound containing nitrogen and element M. α M β By using a compound represented by N as a raw material, it is possible to prevent nitrogen from being released outside the system during the production process of the solid electrolyte. First-principles calculations can be used to select element A and element M that will provide such an effect. Below, a method for selecting raw material compounds to be used in the production of the solid electrolyte will be described.

[0072] In this embodiment, raw material compounds are selected according to the procedures (1) to (3). (1) A candidate material is selected that contains nitrogen, an element A', and an element M', and the first neighboring atoms of the element A' and the element M' are nitrogen. (2) Using first-principles calculations, we estimate the nitrogen defect formation energy E Ndefect Calculate. (3) E above Ndefect is 4.00 eV or more, the candidate material is selected as the raw material compound.

[0073] First-principles calculations are a computational method for predicting physical properties non-empirically, and are a technique that can calculate the total energy and electron energy band structure of a model containing atoms whose atomic numbers and spatial coordinates are known. Calculating the forces acting on atoms enables structural optimization, and also allows calculation of lattice constants, stable structures at 0 K, band gaps, etc. Calculation methods can be broadly divided into two types: "wave function theory" and "density functional theory." The calculation method used in this specification is based on density functional theory.

[0074] Nitrogen defect formation energy E Ndefect is the energy value required to remove nitrogen from the crystal structure and generate defects. The defect formation energy of nitrogen is the total energy E of the crystal structure without defects. perfectand the total energy E of the crystal structure containing nitrogen vacancies Nvacancy and the chemical potential of the nitrogen atom μ N and is defined by the following formula (1). E Ndefect =(E Nvacancy +μ N )-E perfect (1) That is, the nitrogen defect formation energy E Ndefect The procedure for calculating is as follows: (a) Obtain the composition and crystal structure of the candidate material. (b) Chemical potential μ of the nitrogen atom that is desorbed as a defect N Calculate. (c) The total energy E of a defect-free crystal structure perfect is calculated by structural optimization calculation. (d) Total energy E of the crystal structure containing nitrogen vacancies Nvacancy is calculated by structural optimization calculation. (e) The nitrogen defect formation energy E according to equation (1) Ndefect Calculate. If there are multiple nitrogen occupied sites in the crystal structure of the candidate material, E Ndefect The lowest value is the E of the candidate material. Ndefect Used as. The composition and crystal structure of the candidate material can be arbitrarily selected from those available in publicly known publications, databases, etc. The candidate material is not particularly limited as long as it is a compound containing nitrogen, element A', and element M', but is preferably a compound that is stable at room temperature and normal pressure.

[0075] In this embodiment, element A' is a metal element. Element M' is an element other than nitrogen that belongs to any of groups 2 to 15 of the periodic table and is different from element A'. N is a nitrogen element. The element A' is not particularly limited, but is preferably any one of an alkali metal element, an alkaline earth metal element, and an aluminum element, more preferably at least one element selected from lithium, sodium, potassium, magnesium, calcium, and aluminum, and even more preferably lithium, which makes it easier to use the solid electrolyte as a solid electrolyte for an electricity storage device.

[0076] In this embodiment, Li α M' β The defect formation energy of nitrogen is calculated for a candidate material represented by N (α and β are values ​​that give the stoichiometric ratio depending on the type of element M) and Li3N. As an example, lithium is selected as element A'. As element M', boron, magnesium, aluminum, silicon, phosphorus, calcium, strontium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, zinc, gallium, germanium, strontium, yttrium, zirconium, niobium, indium, tin, cerium, hafnium, tantalum, and carbon are selected.

[0077] The first-principles calculations were performed using the Vienna Ab-initio Simulation Package (VASP) software. The calculation conditions were as follows: The k-point was set so that the k-resolution value was approximately 1000. The k-resolution is the product of the number of atoms in the model and the k-points in the a, b, and c axis directions. Cutoff energy of plane wave basis functions: 520 eV Approximation method for exchange-correlation interactions: GGA+U Pseudopotential: PAW(PBEsol) k point: k-resolution≒1000 Convergence condition for SCF calculation: 10 -4 eV Occupancy rate of each atomic site (Occ.): 1 The 3d orbital is the outermost orbital, and in the state of a cation with a stable valence, the 3d orbital is not a closed shell, and electrons exist in the 3d orbital. For the first-principles calculations of materials containing vanadium, chromium, manganese, iron, cobalt, and nickel, which are transition metal elements, the Hubbard U eff The values ​​are used as calculation conditions. This allows the localization effect of electrons in the d orbital to be reflected in the calculation. eff The values ​​are taken from the calculation conditions of first-principles calculations performed in the crystal structure database Materials Project (https: / / materialsproject.org / #search / materials) (as of August 22, 2019). The Ueff values ​​were obtained by searching the database for materials containing vanadium, chromium, manganese, iron, cobalt, and nickel.

[0078] [Table 1]

[0079] In step (d) above, in order to reduce interactions between nitrogen vacancies, the calculation model cell is designed so that the lattice constants a, b, and c are all approximately 10 Å, with the total number of atoms not exceeding 200. Table 2 shows the lattice constants used in calculations for some candidate materials.

[0080] [Table 2]

[0081] Table 3 shows the element M', the chemical composition of each candidate material, and the nitrogen defect formation energy E Ndefect Shows.

[0082] [Table 3]

[0083] From Table 3, the nitrogen defect formation energy E NdefectIn addition, vanadium, yttrium, gallium, calcium, cerium, tin, zinc, germanium, chromium, manganese, strontium, indium, cobalt, nickel and iron have the same valence energy as Li α M' β Nitrogen defect formation energy E in N Ndefect Therefore, it is predicted that candidate materials containing any of vanadium, yttrium, gallium, calcium, cerium, tin, zinc, germanium, chromium, manganese, strontium, indium, cobalt, nickel, and iron as the element M' are likely to generate nitrogen defects and have little effect in suppressing the release of nitrogen out of the system during the solid electrolyte manufacturing process. On the other hand, the elements aluminum, tantalum, silicon, scandium, magnesium, niobium, boron, hafnium, carbon, zirconium and titanium are Li α M' β Nitrogen defect formation energy E in N Ndefect It can be seen that the potential difference is as large as 4.00 eV or more. Therefore, it is predicted that if the candidate material contains any of aluminum, tantalum, silicon, scandium, magnesium, niobium, boron, hafnium, carbon, zirconium, and titanium as the element M', nitrogen defects are unlikely to be generated, and the effect of the present invention, that is, suppressing the emission of nitrogen to the outside of the system during the production process of the solid electrolyte, is highly likely to be exhibited.

[0084] The candidate materials are those with nitrogen defect formation energy E Ndefect It is predicted that the larger the value of , the less likely nitrogen defects are to be generated, and the more likely it is that nitrogen will be released from the system during the solid electrolyte manufacturing process. Ndefect is 4.00 eV or more, preferably 4.10 eV or more, more preferably 4.20 eV or more, even more preferably 4.30 eV or more, and particularly preferably 4.35 eV or more.

[0085] In this embodiment, calculations are performed for the case where element A' contains lithium. α M' β The first-principles calculations are performed using N as a model. However, the element A' may be any metal element, and for example, a candidate material containing any of sodium, potassium, magnesium, calcium, and aluminum may be selected as the element A', and a raw material compound may be selected using the first-principles calculations.

[0086] <Energy storage element> An all-solid-state battery will be specifically described below as one embodiment of the energy storage element of the present invention. The energy storage element 10 of FIG. 1 is an all-solid-state battery, and is a secondary battery in which a positive electrode layer 1 and a negative electrode layer 2 are arranged with an isolation layer 3 interposed therebetween. The positive electrode layer 1 has a positive electrode substrate 4 and a positive electrode active material layer 5, with the positive electrode substrate 4 being the outermost layer of the positive electrode layer 1. The negative electrode layer 2 has a negative electrode substrate 7 and a negative electrode active material layer 6, with the negative electrode substrate 7 being the outermost layer of the negative electrode layer 2. In the energy storage element 10 shown in FIG. 1, the negative electrode active material layer 6, isolation layer 3, positive electrode active material layer 5, and positive electrode substrate 4 are stacked in this order on the negative electrode substrate 7.

[0087] The energy storage device 10 contains a solid electrolyte according to one embodiment of the present invention in at least one of the positive electrode layer 1, the negative electrode layer 2, and the separator layer 3. More specifically, the solid electrolyte according to one embodiment of the present invention is contained in at least one of the positive electrode active material layer 5, the negative electrode active material layer 6, and the separator layer 3. Because the energy storage device 10 contains this solid electrolyte, which has high water resistance, reaction with water is suppressed even when exposed to the atmosphere during the manufacturing process, and the energy storage device 10 can exhibit good charge / discharge performance.

[0088] The energy storage element 10 may be configured to use a solid electrolyte other than the solid electrolyte according to one embodiment of the present invention. Examples of the other solid electrolyte include sulfide-based solid electrolytes other than the solid electrolyte, oxide-based solid electrolytes, dry polymer electrolytes, gel polymer electrolytes, and pseudo-solid electrolytes, with sulfide-based solid electrolytes being preferred. Furthermore, a single layer of the energy storage element 10 may contain multiple different types of solid electrolytes, or each layer may contain a different solid electrolyte.

[0089] Examples of sulfide-based solid electrolytes 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 Ge, Zn, or Ga.), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li x MO y (where x and y are positive numbers, and M is one of P, Si, Ge, B, Al, Ga, and In.) Li 10 GeP2S 12 The following can be mentioned:

[0090] [Positive electrode layer] The positive electrode layer 1 includes a positive electrode substrate 4 and a positive electrode active material layer 5 laminated on the surface of the positive electrode substrate 4. The positive electrode layer 1 may have an intermediate layer between the positive electrode substrate 4 and the positive electrode active material layer 5. The intermediate layer may be, for example, a layer containing conductive particles and a resin binder.

[0091] (Positive electrode substrate) The positive electrode substrate 4 has electrical conductivity. The term "electrically conductive" means that the volume resistivity measured in accordance with JIS-H-0505 (1975) is 10 7 "Non-conductive" means that the volume resistivity is 10 Ω·cm or less. 7This means that the resistance exceeds Ω·cm. The material for the positive electrode substrate 4 may be a metal such as aluminum, titanium, tantalum, indium, or stainless steel, or an alloy thereof. Among these, aluminum or an aluminum alloy is preferred from the viewpoints of potential resistance, high conductivity, and cost. The positive electrode substrate 4 may be a foil, a vapor-deposited film, or the like, with foil being preferred from the viewpoint of cost. Therefore, aluminum foil or an aluminum alloy foil is preferred for the positive electrode substrate 4. Examples of aluminum or aluminum alloys include A1085P and A3003P as specified in JIS-H-4000 (2014).

[0092] The average thickness of the positive electrode substrate 4 is preferably 3 μm to 50 μm, more preferably 5 μm to 40 μm, even more preferably 8 μm to 30 μm, and particularly preferably 10 μm to 25 μm. By setting the average thickness of the positive electrode substrate 4 within the above range, the strength of the positive electrode substrate 4 can be increased while increasing the energy density per volume of the energy storage device 10. The "average thickness" of the positive electrode substrate 4 and the negative electrode substrate 7 described below refers to the value obtained by dividing the mass of the substrate for a given area by the true density and area of ​​the substrate.

[0093] The intermediate layer is a layer disposed between the positive electrode substrate 4 and the positive electrode active material layer 5. The intermediate layer contains conductive particles such as carbon particles, thereby reducing the contact resistance between the positive electrode substrate 4 and the positive electrode active material layer 5. The configuration of the intermediate layer is not particularly limited, and may contain, for example, a resin binder and conductive particles.

[0094] (Cathode active material layer) The positive electrode active material layer 5 contains a positive electrode active material. The positive electrode active material layer 5 can be formed from a so-called positive electrode mixture containing the positive electrode active material. The positive electrode active material layer 5 may contain a mixture or composite containing a positive electrode active material and a solid electrolyte. The positive electrode active material layer 5 may contain optional components such as a conductive agent, a binder, a thickener, and a filler, as necessary. One or more of these optional components may not be substantially contained in the positive electrode active material layer 5.

[0095] The positive electrode active material contained in the positive electrode active material layer 5 can be appropriately selected from known positive electrode active materials commonly used in lithium ion secondary batteries and all-solid-state batteries. Materials capable of absorbing and releasing lithium ions are typically used as the positive electrode active material. Examples of the positive electrode active material include lithium transition metal composite oxides having an α-NaFeO2 crystal structure, lithium transition metal composite oxides having a spinel crystal structure, polyanion compounds, chalcogen compounds, and sulfur. Examples of lithium transition metal composite oxides having an α-NaFeO2 crystal structure include Li[Li 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), 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). Lithium transition metal composite oxides with spinel crystal structure include Li x Mn2O4, Li x Ni γ Mn (2-γ) Examples of polyanion compounds include LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4, Li3V2(PO4)3, Li2MnSiO4, and Li2CoPO4F. Examples of chalcogen compounds include titanium disulfide, molybdenum disulfide, and molybdenum dioxide. Atoms or polyanions in these materials may be partially substituted with atoms or anion species of other elements. The surface of the positive electrode active material may be coated with an oxide such as lithium niobate, lithium titanate, or lithium phosphate. In the positive electrode active material layer, one type of these positive electrode active materials may be used alone, or two or more types may be used in combination.

[0096] The average particle size of the positive electrode active material is preferably, for example, 0.1 μm or more and 20 μm or less. By setting the average particle size of the positive electrode active material to the above lower limit or more, the positive electrode active material becomes easier to manufacture and handle. By setting the average particle size of the positive electrode active material to the above upper limit or less, the electronic conductivity of the positive electrode active material layer 5 improves. Here, the "average particle size" refers to the value at which the volume-based cumulative distribution calculated in accordance with JIS-Z-8819-2 (2001) is 50%, based on the particle size distribution measured in accordance with JIS-Z-8825 (2013) using a laser diffraction / scattering method for a diluted solution obtained by diluting particles with a solvent.

[0097] To obtain particles of a predetermined shape, a pulverizer, a classifier, or the like is used. Examples of pulverization methods include methods using a mortar, a ball mill, a sand mill, a vibration ball mill, a planetary ball mill, a jet mill, a counter jet mill, a swirling airflow jet mill, or a sieve. Wet pulverization in the presence of water or an organic solvent such as heptane can also be used. As a classification method, a sieve, an air classifier, or the like is used as needed for both dry and wet methods.

[0098] The content of the positive electrode active material in the positive electrode active material layer 5 is preferably 10% by mass or more and 95% by mass or less, more preferably 30% by mass or more, and even more preferably 50% by mass or more. By setting the content of the positive electrode active material within this range, the electric capacity of the energy storage element 10 can be further increased.

[0099] When the positive electrode active material layer 5 contains a solid electrolyte, the content of the solid electrolyte is preferably 10% by mass or more and 90% by mass or less, more preferably 20% by mass or more and 70% by mass or less, and even more preferably 50% by mass or less. By setting the content of the solid electrolyte within the above range, the electric capacity of the energy storage device can be increased. When the solid electrolyte according to one embodiment of the present invention is used in the positive electrode active material layer 5, the content of the solid electrolyte according to one embodiment of the present invention relative to the total solid electrolyte in the positive electrode active material layer 5 is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, and even more preferably substantially 100% by mass.

[0100] The mixture of the positive electrode active material and the solid electrolyte is a mixture prepared by mixing the positive electrode active material and the solid electrolyte by mechanical milling or the like. For example, the mixture of the positive electrode active material and the solid electrolyte can be obtained by mixing a particulate positive electrode active material with a particulate solid electrolyte. Examples of the composite of the positive electrode active material and the solid electrolyte include a composite in which the positive electrode active material and the solid electrolyte are chemically or physically bonded, and a composite in which the positive electrode active material and the solid electrolyte are mechanically combined. The composite is a composite in which the positive electrode active material and the solid electrolyte are present within a single particle, such as a composite in which the positive electrode active material and the solid electrolyte are in an aggregated state, or a composite in which a solid electrolyte-containing coating is formed on at least a portion of the surface of the positive electrode active material.

[0101] The conductive agent is not particularly limited as long as it is a material having electrical conductivity. Examples of such conductive agents include carbonaceous materials, metals, and conductive ceramics. Examples of carbonaceous materials include graphitized carbon, non-graphitized carbon, and graphene-based carbon. Examples of non-graphitized 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 (CNTs), and fullerenes. The conductive agent may be in the form of powder or fiber. As the conductive agent, one of these materials may be used alone, or two or more may be mixed. These materials may also be used in combination. For example, a composite of carbon black and CNTs may be used. Among these, carbon black is preferred from the viewpoints of electronic conductivity and coatability, and acetylene black is particularly preferred.

[0102] The content of the conductive agent in the positive electrode active material layer 5 is preferably 1% by mass or more and 10% by mass or less, and more preferably 3% by mass or more and 9% by mass or less. By setting the content of the conductive agent within this range, the electric capacity of the energy storage element 10 can be increased.

[0103] Examples of binders include thermoplastic resins such as fluororesins (polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), etc.), polyethylene, polypropylene, polyimide, poly(meth)acrylic acid, poly(meth)acrylic acid ester, and poly(meth)acrylamide; elastomers such as ethylene-propylene-diene rubber (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), and fluororubber; and polysaccharide polymers.

[0104] The content of the binder in the positive electrode active material layer 5 is preferably 1% by mass to 10% by mass, and more preferably 3% by mass to 9% by mass. By setting the binder content within the above range, the active material can be stably held.

[0105] Examples of thickeners include polysaccharide polymers such as carboxymethyl cellulose (CMC), methyl cellulose, etc. When the thickener has a functional group that reacts with lithium or the like, this functional group may be deactivated in advance by methylation or the like.

[0106] The filler is not particularly limited, and examples of the filler include polyolefins such as polypropylene and polyethylene, inorganic oxides such as silicon dioxide, aluminum oxide, 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, substances derived from mineral resources such as talc, montmorillonite, boehmite, zeolite, apatite, kaolin, mullite, spinel, olivine, sericite, bentonite, and mica, and artificial products thereof.

[0107] The positive electrode active material layer 5 may contain typical non-metallic elements such as B, N, P, F, Cl, Br, and I; typical metallic elements such as Li, Na, Mg, Al, K, Ca, Zn, Ga, Ge, Sn, Sr, and Ba; and transition metal elements such as Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, Nb, and W as components other than the positive electrode active material, conductive agent, binder, thickener, and filler.

[0108] The average thickness of the positive electrode active material layer 5 is preferably 30 μm or more and 1,000 μm or less, and more preferably 60 μm or more and 500 μm or less. By setting the average thickness of the positive electrode active material layer 5 to be equal to or greater than the above lower limit, it is possible to obtain an energy storage device 10 having a high energy density. By setting the average thickness of the positive electrode active material layer 5 to be equal to or less than the above upper limit, it is possible to reduce the size of the energy storage device 10. The average thickness of the positive electrode active material layer 5 is the average value of thicknesses measured at any five positions. The same applies to the average thicknesses of the negative electrode active material layer 6 and the separator layer 3 described below.

[0109] [Negative electrode layer] The negative electrode layer 2 has a negative electrode substrate 7 and a negative electrode active material layer 6 disposed on the negative electrode substrate 7 directly or via an intermediate layer. The configuration of the intermediate layer is not particularly limited and can be selected from the configurations exemplified for the positive electrode layer 1, for example.

[0110] (negative electrode substrate) The negative electrode substrate 7 is electrically conductive. Metals such as copper, nickel, stainless steel, nickel-plated steel, and aluminum, or alloys thereof, are used as the material for the negative electrode substrate 7. Among these, copper or copper alloys are preferred. Examples of the negative electrode substrate include foils and vapor-deposited films, with foils being preferred from the viewpoint of cost. Therefore, copper foil or copper alloy foil is preferred as the negative electrode substrate. Examples of copper foil include rolled copper foil and electrolytic copper foil.

[0111] The average thickness of the negative electrode substrate 7 is preferably 2 μm to 35 μm, more preferably 3 μm to 30 μm, even more preferably 4 μm to 25 μm, and particularly preferably 5 μm to 20 μm. By setting the average thickness of the negative electrode substrate 7 to be equal to or greater than the above lower limit, the strength of the negative electrode substrate 7 can be increased. By setting the average thickness of the negative electrode substrate 7 to be equal to or less than the above upper limit, the energy density per volume of the energy storage device 10 can be increased.

[0112] (Negative electrode active material layer) 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 mixture containing the negative electrode active material. The negative electrode active material layer 6 may contain a mixture or composite containing a negative electrode active material and a solid electrolyte. The negative electrode active material layer 6 contains optional components such as a conductive agent, a binder, a thickener, and a filler, as needed. The types and suitable contents of these optional components in the negative electrode active material layer 6 are the same as those of the optional components in the positive electrode active material layer 5 described above. One or more of these optional components may not be substantially present in the negative electrode active material layer 6.

[0113] The negative electrode active material layer 6 may contain typical non-metallic elements such as B, N, P, F, Cl, Br, and I; typical metallic elements such as Li, Na, Mg, Al, K, Ca, Zn, Ga, Ge, Sn, Sr, and Ba; and transition metal elements such as Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, Ta, Hf, Nb, and W as components other than the negative electrode active material, conductive agent, binder, thickener, and filler.

[0114] The negative electrode active material can be appropriately selected from known negative electrode active materials commonly used in lithium ion secondary batteries and all-solid-state batteries. Materials capable of absorbing and releasing lithium ions are typically used as the negative electrode active material. Examples of the negative electrode active material include metallic Li; metals or semimetals such as Si and Sn; metal oxides or semimetal oxides such as Si oxide, Ti oxide, and Sn oxide; and Li4Ti5O. 12 , LiTiO 2、Examples of the material include titanium-containing oxides such as TiNbO; polyphosphate compounds; silicon carbide; and carbon materials such as graphite and non-graphitic carbon (easily graphitizable carbon or non-graphitizable carbon). Among these materials, graphite and non-graphitic carbon are preferred. In the negative electrode active material layer 6, one of these materials may be used alone, or two or more may be used in combination.

[0115] "Graphite" refers to a graphite material that has an average lattice spacing (d 002 ) is 0.33 nm or more and less than 0.34 nm. Examples of graphite include natural graphite and artificial graphite. Artificial graphite is preferred from the viewpoint of being able to obtain a material with stable physical properties.

[0116] "Non-graphitic carbon" refers to carbon that has an average lattice spacing (d 002 ) is 0.34 nm or more and 0.42 nm or less. Non-graphitic carbon includes non-graphitizable carbon and graphitizable carbon. Examples of non-graphitic carbon include resin-derived materials, petroleum pitch-derived materials, and alcohol-derived materials.

[0117] Here, the "discharged state" refers to a state in which an open circuit voltage is 0.7 V or higher in a single-electrode battery using a negative electrode containing a carbon material as the negative electrode active material as a working electrode and metallic Li as a counter electrode. Since the potential of the metallic Li counter electrode in the open circuit state is approximately equal to the redox potential of Li, the open circuit voltage in the single-electrode battery is approximately equal to the potential of the negative electrode containing the carbon material relative to the redox potential of Li. In other words, an open circuit voltage of 0.7 V or higher in the single-electrode battery means that lithium ions capable of being absorbed and released during charging and discharging have been sufficiently released from the carbon material, which is the negative electrode active material.

[0118] "Non-graphitizable carbon" means the above d 002 This refers to carbon materials with a particle size of 0.36 nm or more and 0.42 nm or less.

[0119] "Graphitizable carbon" means the above d 002 This refers to carbon materials with a particle size of 0.34 nm or more and less than 0.36 nm.

[0120] The negative electrode active material is usually in the form of particles (powder). The average particle size of the negative electrode active material can be, for example, 1 nm or more and 100 μm or less. When the negative electrode active material is, for example, a carbon material, the average particle size may preferably be 1 μm or more and 100 μm or less. When the negative electrode active material is a metal, semi-metal, metal oxide, semi-metal oxide, titanium-containing oxide, polyphosphate compound, or the like, the average particle size may preferably be 1 nm or more and 1 μm or less. By setting the average particle size of the negative electrode active material to be equal to or greater than the above lower limit, the production and handling of the negative electrode active material becomes easier. By setting the average particle size of the negative electrode active material to be equal to or less than the above upper limit, the electronic conductivity of the active material layer is improved. To obtain powder with a predetermined particle size, a pulverizer, a classifier, or the like is used. The pulverization method and powder classification method can be selected, for example, from the methods exemplified for the positive electrode layer 1.

[0121] The content of the negative electrode active material in the negative electrode active material layer 6 is preferably 10% by mass or more and 95% by mass or less, more preferably 30% by mass or more, and even more preferably 50% by mass or more. By setting the content of the negative electrode active material within this range, the electric capacity of the energy storage element 10 can be further increased.

[0122] When the negative electrode active material layer 6 contains a solid electrolyte, the content of the solid electrolyte is preferably 10% by mass or more and 90% by mass or less, more preferably 20% by mass or more and 70% by mass or less, and even more preferably 50% by mass or less. By setting the content of the solid electrolyte within the above range, the electric capacity of the energy storage device 10 can be increased. When the solid electrolyte according to one embodiment of the present invention is used in the negative electrode active material layer 6, the content of the solid electrolyte according to one embodiment of the present invention relative to the total solid electrolyte in the negative electrode active material layer 6 is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, and even more preferably substantially 100% by mass.

[0123] The mixture or composite of the negative electrode active material and solid electrolyte may be the same as the mixture or composite of the positive electrode active material and solid electrolyte described above, except that the positive electrode active material is replaced with the negative electrode active material.

[0124] The average thickness of the negative electrode active material layer 6 is preferably 30 μm or more and 1,000 μm or less, and more preferably 60 μm or more and 500 μm or less. By setting the average thickness of the negative electrode active material layer 6 to be equal to or greater than the above lower limit, it is possible to obtain an energy storage device 10 having a high energy density. By setting the average thickness of the negative electrode active material layer 6 to be equal to or less than the above upper limit, it is possible to reduce the size of the energy storage device 10.

[0125] [Isolation layer] The separator 3 contains a solid electrolyte. As the solid electrolyte contained in the separator 3, various solid electrolytes can be used in addition to the solid electrolyte according to one embodiment of the present invention described above, and among them, it is preferable to use a sulfide-based solid electrolyte. The content of the solid electrolyte in the separator 3 is preferably 70% by mass or more, more preferably 90% by mass or more, even more preferably 99% by mass or more, and sometimes even more preferably substantially 100% by mass. Furthermore, when the separator 3 uses the solid electrolyte according to one embodiment of the present invention, the content of the solid electrolyte according to one embodiment of the present invention relative to the total solid electrolyte in the separator 3 is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, and even more preferably substantially 100% by mass.

[0126] The separator 3 may contain optional components such as an oxide such as LiPO, a halogen compound, a binder, a thickener, a filler, etc. The optional components such as the binder, the thickener, and the filler can be selected from the materials exemplified for the positive electrode active material layer 5.

[0127] The average thickness of the separator 3 is preferably 1 μm or more and 50 μm or less, and more preferably 3 μm or more and 20 μm or less. By setting the average thickness of the separator 3 to be equal to or greater than the above lower limit, it is possible to reliably insulate the positive electrode layer 1 from the negative electrode layer 2. By setting the average thickness of the separator 3 to be equal to or less than the above upper limit, it is possible to increase the energy density of the energy storage element 10.

[0128] The energy storage element of this embodiment can be mounted as an energy storage unit (battery module) configured by assembling a plurality of energy storage elements in an automobile power source such as an electric vehicle (EV), a hybrid electric vehicle (HEV), or a plug-in hybrid electric vehicle (PHEV), a power source for electronic devices such as a personal computer or a communication terminal, or a power source for power storage, etc. In this case, it is sufficient that the technology according to one embodiment of the present invention is applied to at least one energy storage element included in the energy storage unit.

[0129] 2 shows an example of an energy storage device 30 in which energy storage units 20, each of which is an assembly of two or more electrically connected energy storage elements 10, are further assembled. The energy storage device 30 may include a bus bar (not shown) that electrically connects two or more energy storage elements 10, a bus bar (not shown) that electrically connects two or more energy storage units 20, etc. The energy storage units 20 or the energy storage device 30 may include a status monitoring device (not shown) that monitors the status of one or more energy storage elements.

[0130] <Method of manufacturing an energy storage element> The method for manufacturing an energy storage device according to one embodiment of the present invention can be performed by a commonly known method, except that the solid electrolyte according to one embodiment of the present invention is used to form at least one of the positive electrode layer, separator layer, and negative electrode layer. Specifically, the manufacturing method includes, for example, (1) preparing a positive electrode mixture, (2) preparing a separator material, (3) preparing a negative electrode mixture, and (4) laminating the positive electrode layer, separator layer, and negative electrode layer. Each step will be described in detail below.

[0131] (1) Positive electrode mixture preparation process In this step, a cathode mixture for forming a cathode layer (cathode active material layer) is usually prepared. The method for preparing the cathode mixture is not particularly limited and can be appropriately selected depending on the purpose. Examples include mechanical milling of the cathode mixture material, compression molding of the cathode active material, and sputtering using a target material for the cathode active material. When the cathode mixture contains a mixture or composite containing a cathode active material and a solid electrolyte, this step can include mixing the cathode active material and the solid electrolyte using, for example, mechanical milling to prepare a mixture or composite of the cathode active material and the solid electrolyte.

[0132] (2) Preparation of materials for the isolation layer In this step, a material for forming an isolation layer is usually prepared. When the energy storage device is an all-solid-state battery, the isolation layer material is usually a solid electrolyte. The solid electrolyte as the isolation layer material can be prepared by a conventionally known method. For example, it can be obtained by processing a predetermined material by a mechanical milling method. The isolation layer material may also be prepared by heating predetermined materials to above their melting temperature by a melt quenching method, melt-mixing the two at a predetermined ratio, and then quenching. Other methods for synthesizing the isolation layer material include, for example, a solid-phase method in which the material is sintered under reduced pressure, a liquid-phase method such as solution deposition, a vapor-phase method (PLD), and sintering in an argon atmosphere after mechanical milling.

[0133] (3) Negative electrode mixture preparation process In this step, an anode mixture for forming an anode layer (anode active material layer) is usually prepared. Specific methods for preparing the anode mixture are similar to those for preparing the cathode mixture. When the anode mixture contains a mixture or composite containing an anode active material and a solid electrolyte, this step may include mixing the anode active material and the solid electrolyte using, for example, a mechanical milling method to prepare a mixture or composite of the anode active material and the solid electrolyte.

[0134] (Lamination process) In this process, for example, a positive electrode layer having a positive electrode substrate and a positive electrode active material layer, a separator layer, and a negative electrode layer having a negative electrode substrate and a negative electrode active material layer are laminated. In this process, the positive electrode layer, separator layer, and negative electrode layer may be formed sequentially in this order, or vice versa; the order of forming each layer is not particularly limited. For example, the positive electrode layer is formed by pressure molding a positive electrode substrate and a positive electrode mixture, the separator layer is formed by pressure molding an separator material, and the negative electrode layer is formed by pressure molding a negative electrode substrate and a negative electrode mixture. The positive electrode layer, separator layer, and negative electrode layer may be laminated by pressure molding the positive electrode substrate, the positive electrode mixture, the separator material, the negative electrode mixture, and the negative electrode substrate at the same time. The positive electrode layer and the negative electrode layer may be molded in advance, and then pressure molded and laminated with the separator layer.

[0135] [Other embodiments] The present invention is not limited to the above-described embodiments, and can be embodied in various other forms, including modifications and improvements. For example, the energy storage element according to the present invention may include layers other than the positive electrode layer, the separator layer, and the negative electrode layer. Furthermore, the energy storage element according to the present invention may contain a liquid in one or more of the layers. The energy storage element according to the present invention may be a secondary battery, a capacitor, or the like.

[0136] <Example> The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0137] [Example 1] (2-step synthesis) By the following treatment, the composition formula 90(0.80(0.80(0.70Li2S 0.30P2S5) 0.20Li 3 / 2 Al 1 / 2 N) 0.12LiBr 0.08LiI) 10Li 4 / 3 Sn 1 / 3 S 4 / 3 We synthesized a sulfide solid electrolyte represented by the formula: LiN and AlN were weighed out to a molar ratio of 1.2:1, mixed in a mortar, and then pelletized. Then, the mixture was heat-treated at 750°C for 1 hour to obtain LiN.3 / 2 Al 1 / 2 N was prepared. 3 / 2 Al 1 / 2 X-ray diffraction analysis revealed that the main phase of N is Li. 3 / 2 Al 1 / 2 It was confirmed that N. Next, Li2S (99.98%, Aldrich), P2S5 (99%, Aldrich), and Li 3 / 2 Al 1 / 2 N, LiBr (99.999%, Aldrich), and LiI (99.999%, Aldrich) were weighed out to a molar ratio of 44.8:19.2:16:12:8 and mixed in a mortar. This mixed sample was placed in a sealed 80 mL zirconia pot containing 160 g of 4 mm diameter zirconia balls. Milling was carried out for 45 hours at a revolution speed of 510 rpm using a planetary ball mill (FRITSCH, model number Premium line P-7). This resulted in the production of a glassy compound A (80(0.80(0.70Li2S 0.30P2S5) 0.20Li 3 / 2 Al 1 / 2 N·12LiBr·8LiI) was obtained. Separately, in a glove box with an argon atmosphere at a dew point below -50°C, Li2S (99.98%, Aldrich) and SnS2 (99.9%, Kojundo Chemical Laboratory) were weighed out to a molar ratio of 2:1 and mixed in a mortar. This mixed sample was placed in a sealed 80 mL zirconia pot containing 160 g of zirconia balls with a diameter of 4 mm. Milling was carried out for 40 hours using a planetary ball mill (FRITSCH, model number Premium line P-7) at an orbital speed of 510 rpm. This resulted in the formation of a glassy compound B (Li 4 / 3 Sn 1 / 3 S 4 / 3 ) was obtained. Next, in a glove box with an argon atmosphere at a dew point of -50°C or less, the obtained glassy compound A and glassy compound B were mixed together to form a glassy compound having the composition formula 0.80(0.80(0.70Li2S 0.30P2S5) 0.20Li 3 / 2 Al 1 / 2N) 0.12LiBr 0.08LiI with the formula Li 4 / 3 Sn 1 / 3 S 4 / 3 The mixture was weighed to a molar ratio of 90:10 based on the weight of the powder and mixed in a mortar. This mixed sample was placed in a sealed 80 mL zirconia pot containing 160 g of zirconia balls with a diameter of 4 mm. Milling was performed for 2 hours using a planetary ball mill (FRITSCH, model number Premium line P-7) at an orbital speed of 230 rpm. Heat treatment was then performed for 2 hours at 250°C to obtain the sulfide solid electrolyte of Example 1. The heat treatment temperature was set to a temperature equal to or higher than the crystallization temperature but not higher than 100°C above the crystallization temperature. The crystallization temperature was determined by removing a portion of the milled sample and subjecting it to DSC measurement. The DSC measurement was performed under the following conditions. Specifically, a DSC apparatus (Rigaku, Thermo Plus DSC8230) was used, using a sealed SUS pan, and the temperature was increased from room temperature to 400°C at a heating rate of 10°C / min.

[0138] [Examples 2 to 5, Comparative Example 1] The sulfide solid electrolytes of Examples 2 to 5 and Comparative Example 1 were obtained in the same manner as in Example 1, except that the compositions of the sulfide solid electrolytes were as follows. Example 2: 80 (0.80 (0.80 (0.70LiS 0.30P2S5) 0.20Li 3 / 2 Al 1 / 2 N) 0.12LiBr 0.08LiI) 20Li 4 / 3 Sn 1 / 3 S 4 / 3 , Example 3: 70 (0.80 (0.80 (0.70LiS 0.30P2S5) 0.20Li 3 / 2 Al 1 / 2 N) 0.12LiBr 0.08LiI) 30Li 4 / 3 Sn 1 / 3 S 4 / 3 , Example 4: 60 (0.80 (0.80 (0.70LiS 0.30P2S5) 0.20Li 3 / 2 Al 1 / 2 N) 0.12LiBr 0.08LiI) 40Li4 / 3 Sn 1 / 3 S 4 / 3 , Example 5: 50 (0.80 (0.80 (0.70LiS 0.30P2S5) 0.20Li 3 / 2 Al 1 / 2 N) 0.12LiBr 0.08LiI) 50Li 4 / 3 Sn 1 / 3 S 4 / 3 , Comparative example 1:100(0.80(0.80(0.70Li2S·0.30P2S5)·0.20Li 3 / 2 Al 1 / 2 N) 0.12LiBr 0.08LiI) Comparative Example 1 is a glassy compound A obtained in the same manner as in Example 1. 3 / 2 Al 1 / 2 N·12LiBr·8LiI was heat-treated alone at 250°C for 2 hours to prepare the sulfide solid electrolyte of Comparative Example 1.

[0139] [Example 3'] (One-step synthesis) By the following treatment, the composition formula 70(0.80(0.80(0.70Li2S 0.30P2S5) 0.20Li 3 / 2 Al 1 / 2 N) 0.12LiBr 0.08LiI) 30Li 4 / 3 Sn 1 / 3 S 4 / 3 We synthesized a sulfide solid electrolyte represented by the formula: Li2S (99.98%, Aldrich), P2S5 (99%, Aldrich), and Li 3 / 2 Al 1 / 2 N, LiBr (99.999%, Aldrich), LiI (99.999%, Aldrich), and SnS (99.9%, Kojundo Chemical Laboratory) were weighed out in a molar ratio of 51.4:13.4:11.2:8.4:5.6:10 and mixed in a mortar. 3 / 2 Al 1 / 2N was prepared using the same procedure as in Example 1. This mixed sample was placed in a sealed 80 mL zirconia pot containing 160 g of zirconia balls with a diameter of 4 mm. Milling was performed for 45 hours at an orbital speed of 510 rpm using a planetary ball mill (FRITSCH, model number Premium line P-7). The mixture was then heat-treated at 250°C for 2 hours to obtain the sulfide solid electrolyte of Example 3'.

[0140] [Example 6] By the following treatment, the composition formula 90(0.80(0.75Li2S 0.25P2S5) 0.12LiBr 0.08LiI) 10Li 4 / 3 Sn 1 / 3 S 4 / 3 We synthesized a sulfide solid electrolyte represented by the formula: Li2S (99.98%, Aldrich), P2S5 (99%, Aldrich), LiBr (99.999%, Aldrich), and LiI (99.999%, Aldrich) were weighed in a molar ratio of 60:20:12:8 in an argon atmosphere glove box with a dew point below -50 °C and mixed in a mortar. This mixture was placed in a sealed 80 mL zirconia pot containing 160 g of 4 mm diameter zirconia balls. Milling was performed for 45 hours in a planetary ball mill (FRITSCH, Model Premium line P-7) at a revolution speed of 510 rpm. This yielded the glassy compound C (80(0.75Li2S 0.25P2S5) 12LiBr 8LiI). Separately, in the same manner as in Example 1, a glassy compound B (Li 4 / 3 Sn 1 / 3 S 4 / 3 ) was obtained. Next, in a glove box with an argon atmosphere at a dew point of -50°C or less, the obtained glassy compounds C and B were mixed with each other to obtain a glassy compound having the composition formula 0.80(0.75Li2S 0.25P2S5) 0.12LiBr 0.08LiI and a glassy compound having the composition formula Li 4 / 3 Sn 1 / 3 S 4 / 3The sulfide solid electrolyte of Example 6 was obtained by weighing the sulfide solid electrolyte to a molar ratio of 90:10 based on the weight of the sulfide solid electrolyte and the sulfide solid electrolyte SiO 2 ...

[0141] Comparative Example 2 The glassy compound C (80(0.75Li2S·0.25P2S5)·12LiBr·8LiI) obtained in Example 6 was heat-treated alone at 190°C for 2 hours to prepare the sulfide solid electrolyte of Comparative Example 2.

[0142] [evaluation] (1) Powder X-ray diffraction measurement Using the above method, powder X-ray diffraction measurements were performed on each of the solid electrolytes of the Examples and Comparative Examples. The airtight sample holder used for the X-ray diffraction measurements was a "General-Purpose Atmosphere Separator" manufactured by Rigaku Corporation. Tables 4 and 6 show the crystal structures identified from the X-ray diffraction patterns of each of the solid electrolytes of the Examples and Comparative Examples. In Tables 4 and 6, "HICP" represents a crystalline phase having diffraction peaks in the range of 2θ=20.2°±0.5° and 2θ=23.6°±0.5° in X-ray diffraction measurements using CuKα radiation. "LSS" represents a crystalline phase (Li 4 / 3 Sn 1 / 3 S 4 / 3"β-LPS" refers to a crystalline phase (β-Li3PS4) that exhibits diffraction peaks in the ranges of 2θ = 17.5° ± 0.5°, 2θ = 18.1° ± 0.5°, 2θ = 29.1° ± 0.5°, 2θ = 29.9° ± 0.5°, and 2θ = 31.2° ± 0.5° in X-ray diffraction measurement using CuKα radiation.

[0143] FIG. 3 shows the X-ray diffraction patterns of the solid electrolytes of Examples 1, 3, 3′, and 5 and Comparative Example 1. As the tin content increases, the LSS (Li 4 / 3 Sn 1 / 3 S 4 / 3 It can be seen that the diffraction peak in the range of 2θ = 25.6° ± 0.5° due to HICP becomes higher as the tin content increases. On the other hand, it can be seen that the diffraction peaks in the range of 2θ = 20.2° ± 0.5° and 2θ = 23.6° ± 0.5° due to HICP become lower as the tin content increases.

[0144] (2) Ionic conductivity The ionic conductivity (σ) of each solid electrolyte at 25°C in the examples and comparative examples 25 ) was determined by measuring AC impedance using the method described above using a Bio-Logic VMP-300. The measurement results are shown in Tables 4 and 6.

[0145] (3) Water resistance evaluation The water resistance of each of the solid electrolytes of Examples 1, 3, 3', 4, 6 and Comparative Examples 1 and 2 was evaluated by the following procedure. For each solid electrolyte, the ionic conductivity (σ) at 25°C as described in (2) above was measured. 25a After measuring the ionic conductivity (σ) of each solid electrolyte, the solid electrolyte was left in a dry air atmosphere with a dew point of -35°C for 6 hours. 25b ) was measured in the same manner as in (2) above. Then, each solid electrolyte was dried at 150°C for 1 hour, and the ionic conductivity (σ 25c ) was measured in the same manner as in (2) above. The results of these measurements are shown in Tables 5 and 7. Initial ionic conductivity (σ 25a) after being left in a dry air atmosphere (σ 25b ) ratio (maintenance rate: σ 25b / σ 25a ), and the initial ionic conductivity (σ 25a ) after being left in a dry air atmosphere and then further dried, 25c ) ratio (recovery rate: σ 25c / σ 25a ) are shown in Tables 5 and 7, respectively.

[0146] [Table 4]

[0147] [Table 5]

[0148] [Table 6]

[0149] [Table 7]

[0150] As shown in Tables 5 and 7, the solid electrolytes of the Examples had a recovery rate of ionic conductivity (σ 25c / σ 25a ) is high. It is believed that the solid electrolytes of the Examples contain tin as a constituent element, which makes them highly water resistant and inhibits reaction with water when they come into contact with moisture in the air. Furthermore, the solid electrolytes of the Examples have a high retention rate of ionic conductivity (σ 25b / σ 25a ) is also high, which also indicates that it has high water resistance. As shown in Tables 4 and 5, the ionic conductivity is increased by setting the tin content to a relatively small amount, and it can be seen that by adjusting the tin content, it is possible to achieve a good balance between water resistance and ionic conductivity. In addition, when comparing Example 3 and Example 3', which are solid electrolytes of the same composition, it is found that the pre-existing glassy Li 4 / 3 Sn 1 / 3 S 4 / 3 The solid electrolyte of Example 3, which was synthesized by mixing with other raw material compounds, has a glassy Li 4 / 3 Sn 1 / 3 S 4 / 3 The ionic conductivity and water resistance were slightly better than those of the solid electrolyte of Example 3', which was obtained by synthesizing the ionic conductivity and water resistance of the ionic conductivity and water resistance of the ionic conductivity and water resistance of the solid electrolyte of Example 3' and mixing the ionic conductivity and water resistance of the ionic conductivity and water resistance of the solid electrolyte of Example 3'. However, it can be seen that a solid electrolyte having sufficient ionic conductivity and water resistance can be obtained by either synthesis method. [Industrial Applicability]

[0151] The solid electrolyte according to the present invention is suitably used as a solid electrolyte for an electricity storage element such as an all-solid-state battery. [Explanation of symbols]

[0152] 1 Positive electrode layer 2. Negative electrode layer 3 isolation layer 4. Positive electrode substrate 5 Cathode 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. Containing lithium, phosphorus, sulfur, halogen and tin as constituent elements, the molar ratio of the tin content to the phosphorus content is 0.2 or less, A solid electrolyte with a crystalline structure.

2. 2. The solid electrolyte according to claim 1, wherein the crystalline structure has diffraction peaks in the range of 20.2°±0.5° and 23.6°±0.5° in an X-ray diffraction pattern using CuKα radiation.

3. 3. The solid electrolyte according to claim 1, wherein the crystal structure has a diffraction peak in the range of 25.6°±0.5° in an X-ray diffraction pattern using CuKα radiation.

4. 4. The solid electrolyte according to claim 1, wherein the molar ratio of the tin content to the phosphorus content is 0.05 or more.

5. Further containing nitrogen and element M as constituent elements, 5. The solid electrolyte according to claim 1, wherein the element M is at least one element selected from the group consisting of aluminum, tantalum, silicon, scandium, magnesium, niobium, boron, hafnium, carbon, zirconium, and titanium.

6. 6. The solid electrolyte according to claim 1, wherein the halogen is at least one selected from the group consisting of bromine and iodine.

7. preparing a composition containing lithium, phosphorus, sulfur, a halogen, and tin, wherein the molar ratio of the tin content to the phosphorus content is 0.2 or less; reacting the composition to obtain an intermediate; heating the intermediate; A method for producing a solid electrolyte comprising:

8. 8. The method for producing a solid electrolyte according to claim 7, wherein the composition contains a compound containing lithium, sulfur, and tin.

9. An electric storage element comprising the solid electrolyte according to any one of claims 1 to 6.

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