Solid electrolyte, material for producing solid electrolyte , method for producing solid electrolyte, and power storage element

Abstract

A solid electrolyte according to one aspect of the present invention contains elemental lithium, elemental phosphorus, elemental silicon, elemental sulfur, and a halogen element. The molar ratio of the elemental silicon content to the total elemental phosphorus and silicon content (Si / (P+Si)) is 0.12 or greater. The halogen element contains elemental bromine and / or elemental iodine, and the molar ratio of the total elemental bromine content and the elemental iodine and halogen element content ((Br+I) / X) is 0.30 or greater. In an X-ray diffraction pattern (CuKα), diffraction peaks are present across a diffraction angle 2θ of 20.0° ± 0.5° and across a diffraction angle 2θ of 29.3° ±0.5°. In the X-ray pattern, either no diffraction peak is not present across a diffraction angle 2θ of 17.5° ±0.5°, or a diffraction peak is present across a diffraction angle 2θ of 17.5° ±0.5°, and the intensity of the diffraction peak across the diffraction angle 2θ of 17.5° ± 0.5° is equal to or less than 1 / 5 the intensity of the diffraction peak across the diffraction angle 2θ of 20.0°± 0.5°.

Description

Solid electrolyte, material for manufacturing solid electrolyte, method for manufacturing solid electrolyte, and energy storage element

[0001] The present invention relates to a solid electrolyte, a material for producing a solid electrolyte, a method for producing a solid electrolyte, and an electricity storage device.

[0002] Due to their high energy density, non-aqueous electrolyte secondary batteries, typified by lithium ion secondary batteries, are widely used in electronic devices such as personal computers and communication terminals, automobiles, etc. Non-aqueous electrolyte secondary batteries generally include an electrode assembly having a pair of electrodes and a separator, a non-aqueous electrolyte, and a container that accommodates the electrode assembly and the non-aqueous electrolyte, and are configured to charge and discharge by transferring charge-transporting ions between the electrodes. Other non-aqueous electrolyte storage elements besides non-aqueous electrolyte secondary batteries include capacitors such as lithium ion capacitors and electric double layer capacitors.

[0003] In recent years, energy storage elements have been proposed that use solid electrolytes such as sulfide solid electrolytes as the nonaqueous electrolyte, instead of nonaqueous electrolyte solutions in which an electrolyte salt is dissolved in a liquid such as an organic solvent. Patent Document 1 describes a sulfide solid electrolyte that contains lithium, phosphorus, and sulfur and has a crystalline structure.

[0004] Japanese Patent Application Laid-Open No. 2005-228570

[0005] In the production of a solid electrolyte having a predetermined composition, a heat treatment may be performed to precipitate a high ion conduction phase (HICP), thereby obtaining a solid electrolyte with high ionic conductivity. However, when such a solid electrolyte is exposed to a temperature higher than the temperature at which the HICP precipitates, the HICP may undergo a phase transition to a low ion conduction phase (LICP) or the like. In the case of a solid electrolyte that has low heat resistance and is prone to undergo a phase transition, the heat treatment must be performed with precise temperature control to prevent the phase transition to the LICP, resulting in low productivity.

[0006] An object of the present invention is to provide a solid electrolyte having high heat resistance, a material for producing a solid electrolyte capable of producing such a solid electrolyte, a method for producing a solid electrolyte, and an energy storage element using such a solid electrolyte.

[0007] A solid electrolyte according to one aspect of the present invention contains lithium, phosphorus, silicon, sulfur, and a halogen, wherein the molar ratio (Si / (P+Si)) of the content of the silicon element to the total content of the phosphorus and the silicon element is 0.12 or more, the halogen element includes at least one of bromine and iodine, and the molar ratio ((Br+I) / X) of the total content of the bromine and iodine element to the content of the halogen element is 0.80 or more, and when measured with CuKα radiation, In the X-ray diffraction pattern used, there are diffraction peaks in the range of a diffraction angle 2θ of 20.0°±0.5° and in the range of a diffraction angle 2θ of 29.3°±0.5°, and in the X-ray diffraction pattern, there is no diffraction peak in the range of a diffraction angle 2θ of 17.5°±0.5°, or there is a diffraction peak in the range of a diffraction angle 2θ of 17.5°±0.5°, and the intensity of the diffraction peak in the range of a diffraction angle 2θ of 17.5°±0.5° is ⅕ or less of the intensity of the diffraction peak in the range of a diffraction angle 2θ of 20.0°±0.5°.

[0008] A material for producing a solid electrolyte according to another aspect of the present invention contains lithium, phosphorus, silicon, sulfur, and a halogen, wherein the molar ratio (Si / (P+Si)) of the content of the silicon element to the total content of the phosphorus and the silicon element is 0.12 or more, the halogen element includes at least one of bromine and iodine, and the molar ratio ((Br+I) / X) of the total content of the bromine and the iodine element to the content of the halogen element is 0.80 or more, the material has one or more crystallization temperatures in the range of 150°C to 400°C, and has an ionic conductivity σ at 25°C after being heat-treated for 2 hours at T1°C, which is the lowest temperature among the one or more crystallization temperatures. Ｔ１ Ionic conductivity σ at 25 ° C. after heat treatment at (T1 + 40) ° C. for 2 hours Ｔ１＋４０ The ratio of (σ Ｔ１＋４０ / σ Ｔ１ ) is 0.7 or more.

[0009] A method for producing a solid electrolyte according to another aspect of the present invention includes heat-treating the material for producing a solid electrolyte according to the aspect of the present invention, and the heat-treating includes a time period during which the material is maintained at a temperature equal to or higher than T1°C.

[0010] A method for producing a solid electrolyte according to another aspect of the present invention includes heat treating a material for producing a solid electrolyte, the material for producing the solid electrolyte containing lithium, phosphorus, silicon, sulfur, and a halogen, wherein the molar ratio (Si / (P+Si)) of the content of the silicon element to the total content of the phosphorus and the silicon element is 0.12 or more, the halogen element includes at least one of bromine and iodine, and the molar ratio ((Br+I) / X) of the total content of the bromine and the iodine element to the content of the halogen element is 0.80 or more, the heat treating includes a time period during which the material is maintained at a temperature of 200°C or higher, and the maximum temperature in the heat treating is 400°C or lower.

[0011] A solid electrolyte according to another aspect of the present invention is obtained by the method for producing a solid electrolyte according to any one aspect of the present invention.

[0012] An electric storage device according to another aspect of the present invention contains the solid electrolyte according to the aspect of the present invention.

[0013] According to any one aspect of the present invention, it is possible to provide a solid electrolyte having high heat resistance, a material for producing a solid electrolyte that can produce such a solid electrolyte, a method for producing a solid electrolyte, and an energy storage element that uses such a solid electrolyte.

[0014] FIG. 1 is a schematic cross-sectional view showing an all-solid-state battery that is one embodiment of the energy storage element of the present invention. FIG. 2 is a schematic diagram showing an energy storage device including energy storage elements according to several embodiments of the present invention. FIG. 3 shows DSC curves for the solid electrolyte manufacturing materials of Comparative Examples 1 to 3 and Examples 2 to 6. FIG. 4 shows X-ray diffraction patterns for the solid electrolytes of Comparative Example 1-1, Comparative Example 2-1, Comparative Example 3-1, Example 2-1, Example 3-1, Example 4-1, Example 5-1, and Example 6-1. FIG. 5 shows X-ray diffraction patterns for the solid electrolytes of Comparative Example 3-4, Example 2-4, Example 3-3, and Example 4-3. FIG. 6 shows X-ray diffraction patterns for the solid electrolytes of Examples 8-1, 9-1, 10-1, 2-1, and 11-1. FIG. 7 shows X-ray diffraction patterns for the solid electrolytes of Examples 2-1, 17-1, 18-1, 19-1, 20-1, 21-1, and Comparative Example 6-1.

[0015] First, an outline of the solid electrolyte, the material for producing the solid electrolyte, the method for producing the solid electrolyte, and the electricity storage device disclosed in this specification will be described.

[0016] [1] A solid electrolyte according to one aspect of the present invention contains lithium, phosphorus, silicon, sulfur, and a halogen, wherein the molar ratio (Si / (P+Si)) of the content of the silicon element to the total content of the phosphorus and the silicon element is 0.12 or more, the halogen element includes at least one of bromine and iodine, and the molar ratio ((Br+I) / X) of the total content of the bromine and the iodine element to the content of the halogen element is 0.80 or more, and the solid electrolyte is irradiated with CuKα radiation. In an X-ray diffraction pattern obtained using a fluorine-containing fluoride (HF) sample, the sample has diffraction peaks in a diffraction angle 2θ range of 20.0°±0.5° and a diffraction angle 2θ range of 29.3°±0.5°, and in the X-ray diffraction pattern, the sample does not have a diffraction peak in a diffraction angle 2θ range of 17.5°±0.5°, or has a diffraction peak in a diffraction angle 2θ range of 17.5°±0.5°, and the intensity of the diffraction peak in the diffraction angle 2θ range of 17.5°±0.5° is ⅕ or less of the intensity of the diffraction peak in the diffraction angle 2θ range of 20.0°±0.5°.

[0017] The solid electrolyte described in [1] above has high heat resistance. While the reason for this is unclear, the following is presumed. In an X-ray diffraction pattern using CuKα radiation, a crystal structure having diffraction peaks in the diffraction angle 2θ range of 20.0°±0.5° and the diffraction angle 2θ range of 29.3°±0.5° is the high ionic conductivity phase (HICP) described above. In the solid electrolyte described in [1] above, a portion of the phosphorus element is substituted with a predetermined amount of silicon element, which is thought to improve the thermal stability of the HICP. Furthermore, the halogen element necessary for the formation of the HICP is at least one of bromine element and iodine element. In the solid electrolyte described in [1] above, the relatively low amount of halogen elements other than bromine element and iodine element, which are not necessary for the formation of the HICP, is also thought to contribute to the improvement of the thermal stability of the HICP. Furthermore, a crystal structure having a diffraction peak in the range of a diffraction angle 2θ of 17.5°±0.5° in an X-ray diffraction pattern using CuKα radiation is considered to be the above-mentioned low ionic conductive phase (LICP). In the solid electrolyte described in [1] above, LICP is not precipitated or the amount of LICP is relatively small. For these reasons, the solid electrolyte described in [1] above is presumed to have high heat resistance, and has sufficient ionic conductivity even when heat-treated at high temperatures, resulting in high productivity.

[0018] X-ray diffraction patterns using CuKα radiation are obtained by powder X-ray diffraction measurement according to the following procedure. The solid electrolyte powder to be measured is filled into an airtight X-ray diffraction sample holder 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 (Rigaku's "MiniFlex II"). The radiation source is CuKα radiation, the tube voltage is 30 kV, and the tube current is 15 mA. 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. In addition, when it is not possible to perform measurements using the above-mentioned measuring device, other models that are considered to produce equivalent measurement results can be used. The same applies to other measuring devices in this specification.

[0019] The elements contained in the solid electrolyte are quantified by the following methods. Halogens are quantified by combustion ion chromatography. Sulfur is quantified by combustion-infrared absorption spectroscopy (CS meter). Lithium, phosphorus, silicon, and optional elements (elements other than lithium, phosphorus, silicon, sulfur, and halogens) are quantified by inductively coupled plasma atomic emission spectroscopy (ICP-AES). However, among the optional elements, hydrogen and oxygen are quantified by inert gas fusion-infrared absorption spectroscopy. Among the optional elements, nitrogen is quantified by inert gas fusion-thermal conductivity spectroscopy. Among the optional elements, carbon is quantified by combustion-infrared absorption spectroscopy. Note that, when it is impossible to measure each element using the methods described above, other methods that are considered to produce equivalent measurement results can be used.

[0020] [2] In the solid electrolyte according to the above [1], the molar ratio (Si / (P+Si)) may be 0.55 or less.

[0021] The solid electrolyte described in the above [2] has higher heat resistance and also has high ionic conductivity.

[0022] [3] In the solid electrolyte according to the above [1] or [2], the molar ratio (Si / (P+Si)) may be 0.50 or less.

[0023] The solid electrolyte described in the above [3] has higher heat resistance and higher ionic conductivity.

[0024] [4] In the solid electrolyte according to any one of [1] to [3] above, the molar ratio (Li / (P+Si)) of the content of the lithium element to the total content of the phosphorus element and the silicon element may be 3.10 or more and less than 3.70.

[0025] The solid electrolyte described in [4] above has higher heat resistance and ionic conductivity. The reason for the increased ionic conductivity in the solid electrolyte described in [4] above is presumed to be that the lithium ions can move more easily within the crystal structure by substituting a part of the pentavalent phosphorus element with a tetravalent silicon element and setting the lithium element content to a relatively small range.

[0026] [5] The solid electrolyte according to any one of [1] to [4] above may be represented by the following formula (1): Li ａ (P １－ｂ Si ｂ ) S ｃ X ｄ Z ｅ ... (1) (In formula (1), X is a halogen element including at least one of bromine and iodine. Z is at least one element other than Li, P, Si, S, and X. a, b, c, d, and e satisfy the following relationships: 3.00≦a≦3.80, 0.12≦b<1.00, 3.00≦c≦4.20, 0.01≦d≦1.00, and 0≦e≦1.00, respectively.)

[0027] The solid electrolyte described in [5] above has higher heat resistance. It is believed that the content of each element constituting the solid electrolyte described in [1] above affects the heat resistance. However, there is a problem that excellent properties cannot be obtained by examining the content of each element, and better heat resistance cannot be achieved unless the elemental composition of the entire solid electrolyte described in [1] above is examined as a whole. The background to this problem is as follows. It is believed that the solid electrolyte described in [1] above can be made to have an ortho composition or a composition close to it, thereby increasing chemical stability and further improving heat resistance. Here, since the phosphorus element is pentavalent and the silicon element is tetravalent, Li ２ S and P ２ S ５ The solid electrolyte is composed of Li ３ P.S. ４ corresponds to the ortho composition, and Li ２ S and SiS ２ The solid electrolyte is composed of Li ４ SiS ４ corresponds to an ortho-composition. Therefore, in the case of a solid electrolyte in which a portion of the phosphorus element is substituted with silicon element, such as the solid electrolyte described in [1] above, the content of lithium element that can be used to achieve an ortho-composition varies depending on the molar ratio of the phosphorus content to the silicon content. On the other hand, the content of lithium element affects the heat resistance of the solid electrolyte independently of whether it is an ortho-composition. For this reason, it has been difficult to investigate the relationship between the content of each element constituting the solid electrolyte described in [1] above and heat resistance. Furthermore, the content of halogen elements, etc. also affects the heat resistance of the solid electrolyte, which also makes it even more difficult to find a composition for the solid electrolyte described in [1] above. However, after extensive investigation, the present inventors have found that by using the solid electrolyte described in [5] above, which has a composition represented by the above formula (1), the constraints on the content of each closely related element can be overcome and a solid electrolyte with superior heat resistance can be provided.

[0028] [6] In the solid electrolyte according to any one of [1] to [5] above, the ionic conductivity at 25°C may be 1.0 mS / cm or more.

[0029] The solid electrolyte described in the above [6] has high ionic conductivity.

[0030] The ionic conductivity of the solid electrolyte is determined by measuring AC impedance using the following method. In an argon atmosphere with a dew point of −50°C or less, 120 mg of sample powder of the solid electrolyte is placed in a powder molding machine with an inner diameter of 10 mm, and then uniaxially pressed at 10 MPa to 100 MPa using a hydraulic press. If it is difficult to prepare 120 mg of sample powder, less than 120 mg of sample powder may be placed. In this case, a powder molding machine with an inner diameter of less than 10 mm may be used. After releasing the pressure, 120 mg of SUS316L powder is placed on the top surface of the sample as a current collector, and then uniaxially pressed again at 10 MPa to 100 MPa using a hydraulic press. The SUS316L powder used has a mesh size of less than 100 mesh / inch. Next, 120 mg of SUS316L powder was placed on the underside of the sample as a current collector, and the sample was 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 measurements were performed at a predetermined temperature. The results were plotted as a Nyquist plot. For solid electrolytes in which no arc component was observed in the Nyquist plot, the value on the real axis at the measurement point on the highest frequency side was taken as the resistance R. For solid electrolytes in which an arc component was observed in the Nyquist plot, the value on the real axis at the end point on the low frequency side of the arc was taken as the resistance R. 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. Furthermore, 240 mg of SUS316L powder was uniaxially pressed at 360 MPa for 5 minutes to obtain a SUS current collector pellet. Thereafter, the thicknesses of the pellet for measuring ionic conductivity and the SUS current collector pellet are measured using a micrometer, and then the thickness of the SUS current collector pellet is subtracted from the thickness of the pellet for measuring ionic conductivity to calculate the thickness L of the solid electrolyte sample. ２５ (mS / cm) is a function of the resistance R (Ω), the thickness L (cm) of the solid electrolyte sample, and the area A (cm) of the solid electrolyte sample. ２ ) and calculate it by the following formula (A): ２５=1000L / (RA)...(A)

[0031] [7] In the solid electrolyte according to any one of [1] to [6] above, the ionic conductivity at 25°C after heat treatment at 270°C for 2 hours may be 1.0 mS / cm or more.

[0032] The solid electrolyte described in the above [7] has higher heat resistance.

[0033] The heat treatment at 270° C. for 2 hours is carried out in an argon atmosphere with a dew point of −50° C. or lower.

[0034] [8] A material for producing a solid electrolyte according to one aspect of the present invention contains lithium, phosphorus, silicon, sulfur, and a halogen, wherein a molar ratio (Si / (P+Si)) of the content of the silicon element to the total content of the phosphorus and the silicon element is 0.12 or more, the halogen element includes at least one of bromine and iodine, and a molar ratio ((Br+I) / X) of the total content of the bromine and the iodine element to the content of the halogen element is 0.30 or more, the material has one or more crystallization temperatures in the range of 150°C to 400°C, and has an ionic conductivity σ at 25°C after being heat-treated for 2 hours at T1°C, which is the lowest temperature among the one or more crystallization temperatures. Ｔ１ Ionic conductivity σ at 25 ° C. after heat treatment at (T1 + 40) ° C. for 2 hours Ｔ１＋４０ The ratio of (σ Ｔ１＋４０ / σ Ｔ１ ) is 0.7 or more.

[0035] The material for producing a solid electrolyte described in the above [8] can produce a solid electrolyte having high heat resistance. In particular, the material for producing a solid electrolyte described in the above [8] usually has an ionic conductivity σ Ｔ１ In contrast, the ionic conductivity σ after heat treatment at (T1 + 40) ° C., which is 40 ° C. higher than T1 ° C. Ｔ１＋４０ Therefore, in the material for producing a solid electrolyte described in the above [8], even if the material is heat-treated at a temperature somewhat higher than T1°C, a solid electrolyte having sufficient ionic conductivity can be obtained, and productivity is high.

[0036] The "crystallization temperature" is determined by measurement using a differential scanning calorimeter (DSC) according to the following procedure. The sample powder (material for manufacturing a solid electrolyte) to be measured is placed in a stainless steel sealed pan in an argon atmosphere with a dew point of -50°C or less, and then sealed using a dedicated jig. Differential scanning calorimetry is performed using a DSC device (Rigaku's "Thermo Plus DSC8230"). The temperature range is from room temperature to 350°C, and the heating rate is 10°C / min.

[0037] [9] A method for producing a solid electrolyte according to one aspect of the present invention includes heat-treating the material for producing a solid electrolyte according to the above item [8], and the heat-treating includes a time period during which the material is maintained at a temperature equal to or higher than the above T1°C.

[0038] According to the method for producing a solid electrolyte described in the above [9], a solid electrolyte having high heat resistance can be produced.

[0039]

[10] In the method for producing a solid electrolyte according to the above [9], the maximum temperature in the heat treatment may be 400° C. or less.

[0040] The solid electrolyte obtained by the method for producing a solid electrolyte according to the above

[10] can have high heat resistance and sufficient ionic conductivity.

[0041]

[11] A method for producing a solid electrolyte according to one aspect of the present invention includes heat treating a material for producing a solid electrolyte, the material for producing the solid electrolyte containing lithium, phosphorus, silicon, sulfur, and a halogen, wherein a molar ratio (Si / (P+Si)) of the content of the silicon element to the total content of the phosphorus and the silicon element is 0.12 or more, the halogen element includes at least one of bromine and iodine, and a molar ratio ((Br+I) / X) of the total content of the bromine and the iodine element to the content of the halogen element is 0.30 or more, the heat treating includes a time period during which the material is maintained at a temperature of 200°C or higher, and the maximum temperature in the heat treating is 400°C or lower.

[0042] According to the method for producing a solid electrolyte described in

[11] above, a solid electrolyte having high heat resistance can be produced. Furthermore, the solid electrolyte obtained by the method for producing a solid electrolyte described in

[11] above can have sufficient ionic conductivity.

[0043]

[12] A solid electrolyte according to one aspect of the present invention is obtained by the method for producing a solid electrolyte according to any one of the above [9] to

[11] .

[0044] The solid electrolyte described in the above

[12] has high heat resistance.

[0045]

[13] An energy storage element according to one embodiment of the present invention includes the solid electrolyte according to any one of [1] to [7] and

[12] above.

[0046] The electric storage element according to the above

[13] contains a solid electrolyte having high heat resistance, and therefore the electric storage element according to the above

[13] is excellent in productivity.

[0047] A solid electrolyte, a material for manufacturing a solid electrolyte, a method for manufacturing a solid electrolyte, an electricity storage element, a method for manufacturing an electricity storage element, an electricity storage device, and other embodiments according to one embodiment of the present invention will be described in detail below.

[0048] The lower and upper limits of each numerical range described in the embodiments of the present invention can be combined in any manner.

[0049] <Solid Electrolyte> (Composition) A solid electrolyte according to one embodiment of the present invention contains lithium, phosphorus, silicon, sulfur, and a halogen. The solid electrolyte refers to an electrolyte that maintains a solid state at 25°C under a nitrogen atmosphere. The solid electrolyte preferably has lithium ion conductivity. The solid electrolyte may be a sulfide solid electrolyte.

[0050] With regard to the constituent elements of the solid electrolyte, the lower limit of the molar ratio (Si / (P+Si)) of the content of silicon element to the total content of phosphorus element and silicon element is 0.12, preferably 0.15, more preferably 0.18, and still more preferably 0.20. When the molar ratio (Si / (P+Si)) is equal to or greater than the above lower limit, it is possible to improve heat resistance, etc. The lower limit of the molar ratio (Si / (P+Si)) may be 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, or 0.60. The upper limit of the molar ratio (Si / (P+Si)) may be, for example, 0.70, 0.65, or 0.60, but is preferably 0.55, and more preferably 0.50. When the molar ratio (Si / (P+Si)) is equal to or less than the above upper limit, it is possible to improve heat resistance and ionic conductivity, etc. The upper limit of the molar ratio (Si / (P+Si)) may be 0.45, 0.40, 0.35, 0.30, 0.25, or 0.20.

[0051] The lower limit of the molar ratio (S / (P+Si)) of the content of sulfur element to the total content of phosphorus element and silicon element is preferably 3.00, more preferably 3.20, even more preferably 3.30, and even more preferably 3.40, 3.50, 3.60, 3.70 or 3.75. When the molar ratio (S / (P+Si)) is not less than the above lower limit, it is possible to improve heat resistance and ionic conductivity. The lower limit of the molar ratio (S / (P+Si)) may be 3.80, 3.85 or 3.90. The upper limit of the molar ratio (S / (P+Si)) is preferably 4.20, more preferably 4.10, and even more preferably 4.05, 4.00 or 3.95. When the molar ratio (S / (P+Si)) is not more than the above upper limit, it is possible to improve heat resistance and ionic conductivity. The upper limit of the molar ratio (S / (P+Si)) may be 3.90, 3.85, or 3.80.

[0052] The lower limit of the molar ratio (Li / (P+Si)) of the content of lithium element to the total content of phosphorus element and silicon element can be, for example, 3.00 or 3.05, but is preferably 3.10, more preferably 3.15, and even more preferably 3.20. When the molar ratio (Li / (P+Si)) is not less than the above lower limit, it is possible to increase ionic conductivity, etc. The lower limit of the molar ratio (Li / (P+Si)) may be 3.25, 3.30, 3.35, 3.40, 3.45, 3.50, or 3.55. The upper limit of the molar ratio (Li / (P+Si)) can be, for example, 3.80, 3.75, or 3.70, but is preferably 3.65, more preferably 3.60, and even more preferably 3.55. When the molar ratio (Li / (P+Si)) is not more than the above upper limit, it is possible to further increase heat resistance and ionic conductivity, etc. The upper limit of the molar ratio (Li / (P+Si)) may be 3.50, 3.45, 3.40, 3.35, 3.30, 3.25, or 3.20.

[0053] When the molar ratio of the silicon content to the total content of phosphorus and silicon (Si / (P+Si)) is x and the molar ratio of the lithium content to the total content of phosphorus and silicon (Li / (P+Si)) is y, it is preferable that the following formulas (i) and (ii) are satisfied. Furthermore, in addition to the following formulas (i) and (ii), it is more preferable that the following formulas (iii) and (iv) are satisfied, and the molar ratio of the total content of the bromine and iodine elements to the content of the halogen elements ((Br+I) / X) is 0.90 or more. 0.12≦x≦0.35 (i) 3.25≦y≦3.65 (ii) y≧−2x+3.7 (iii) y≧x+3.1 (iv)

[0054] It is more preferable that the following formulae (v) and (vi) are satisfied instead of the above formulae (i) and (ii). It is even more preferable that the following formulae (iii) and (iv) are satisfied in addition to the following formulae (v) and (vi), and the molar ratio of the total content of the bromine element and the iodine element to the content of the halogen element ((Br+I) / X) is 0.90 or more: 0.12≦x≦0.30 (v) 3.30≦y≦3.60 (vi)

[0055] When the solid electrolyte satisfies the above formulas (i) and (ii), more preferably when it satisfies all of the formulas (i) to (iv) and the molar ratio of the total content of the bromine element and the iodine element to the content of the halogen element ((Br + I) / X) is 0.90 or more, the ionic conductivity is further increased. When the solid electrolyte satisfies the above formulas (v) and (vi), more preferably when it satisfies all of the formulas (v), (vi), (iii), and (iv) and the molar ratio of the total content of the bromine element and the iodine element to the content of the halogen element ((Br + I) / X) is 0.90 or more, the ionic conductivity is further increased.

[0056] The lower limit of the molar ratio (X / (P+Si)) of the content of the halogen element (X) to the total content of the phosphorus element and the silicon element is preferably 0.01, more preferably 0.05, even more preferably 0.10, and even more preferably 0.20, 0.30, or 0.40. The upper limit of the molar ratio (X / (P+Si)) is preferably 1.00, more preferably 0.80, even more preferably 0.70, and even more preferably 0.60. By having the molar ratio (X / (P+Si)) within the above range, it is possible to further improve heat resistance and ionic conductivity.

[0057] The halogen element contained in the solid electrolyte includes at least one of bromine and iodine, and preferably includes both bromine and iodine. By using at least one of bromine and iodine as the halogen element, it is possible to improve heat resistance, etc. The solid electrolyte may also include halogen elements other than bromine and iodine (fluorine, chlorine, etc.). The solid electrolyte may also be substantially free of halogen elements other than bromine and iodine (fluorine, chlorine, etc.).

[0058] The lower limit of the molar ratio ((Br+I) / X) of the total content of bromine and iodine elements to the content of halogen elements is 0.30, more preferably 0.40, even more preferably 0.50, and even more preferably 0.60, 0.70, 0.80, 0.90, or 0.95. By setting the molar ratio ((Br+I) / X) to the above lower limit or more, it is possible to improve heat resistance, etc. The upper limit of the molar ratio ((Br+I) / X) may be 1.00.

[0059] The lower limit of the molar ratio of the bromine element content to the halogen element content (Br / X) is preferably 0.10, more preferably 0.30, and even more preferably 0.50. The upper limit of the molar ratio (Br / X) may be 1.00, but is preferably 0.90, more preferably 0.80, and even more preferably 0.70.

[0060] The lower limit of the molar ratio (I / X) of the iodine element content to the halogen element content is preferably 0.10, more preferably 0.20, and even more preferably 0.30. The upper limit of the molar ratio (I / X) may be 1.00, but is preferably 0.80, more preferably 0.60, and even more preferably 0.50.

[0061] The solid electrolyte may be substantially free of chlorine as a halogen element. The upper limit of the molar ratio (Cl / X) of the content of chlorine to the content of halogen elements is preferably 0.60, more preferably 0.50, even more preferably 0.40, and even more preferably 0.30, 0.20, 0.15, 0.10, 0.05, or 0.01. The molar ratio (Cl / X) may be 0. The upper limit of the molar ratio (Cl / (P+Si)) of the content of chlorine to the total content of phosphorus and silicon elements is preferably 0.35, more preferably 0.30, even more preferably 0.25, and even more preferably 0.20, 0.15, 0.10, 0.05, or 0.01. The molar ratio (Cl / (P+Si)) may be 0.

[0062] The solid electrolyte may be substantially free of fluorine as a halogen element. The upper limit of the molar ratio (F / X) of the content of fluorine to the content of halogen elements is preferably 0.60, more preferably 0.50, even more preferably 0.40, and even more preferably 0.30, 0.20, 0.15, 0.10, 0.05, or 0.01. The molar ratio (F / X) may be 0. The upper limit of the molar ratio (F / (P+Si)) of the content of fluorine to the total content of phosphorus and silicon elements is preferably 0.35, more preferably 0.30, even more preferably 0.25, and even more preferably 0.20, 0.15, 0.10, 0.05, or 0.01. The molar ratio (F / (P+Si)) may be 0.

[0063] The solid electrolyte may further contain other elements (Z) other than lithium, phosphorus, silicon, sulfur, and halogens. The other elements (Z) may be one type or two or more types. However, the upper limit of the molar ratio (Z / (P+Si)) of the content of the other elements (Z) to the total content of phosphorus and silicon is preferably 1.00, more preferably 0.50, and even more preferably 0.30, 0.20, 0.10, 0.05, or 0.01. When the solid electrolyte does not contain other elements (Z) or the content of other elements (Z) is low, the essential elements can function effectively, thereby further improving heat resistance and ionic conductivity. The lower limit of the molar ratio (Z / (P+Si)) of the content of the other elements (Z) to the total content of phosphorus and silicon may be 0.00.

[0064] In one embodiment of the present invention, the solid electrolyte may have a low content of nitrogen element as the other element (Z), or may not contain nitrogen element. Furthermore, in one embodiment of the present invention, the solid electrolyte may contain nitrogen element as the other element (Z). The upper limit of the molar ratio (N / (P+Si)) of the content of nitrogen element to the total content of phosphorus element and silicon element may be 0.80, or may be 0.60, 0.40, 0.30, 0.20, 0.10, or 0.05. The lower limit of the molar ratio (N / (P+Si)) may be 0.00, or may be 0.01, 0.02, or 0.05.

[0065] In one embodiment of the present invention, the solid electrolyte may have a low content of oxygen element as the other element (Z), or may not contain oxygen element. Furthermore, in one embodiment of the present invention, the solid electrolyte may contain oxygen element as the other element (Z). The upper limit of the molar ratio (O / (P+Si)) of the content of oxygen element to the total content of phosphorus element and silicon element may be 1.00, or may be 0.80, 0.60, 0.50, 0.30, 0.20, or 0.10. The lower limit of the molar ratio (O / (P+Si)) may be 0.00, or may be 0.01, 0.02, or 0.05.

[0066] The solid electrolyte is preferably represented by the following formula (1): Li ａ (P １－ｂ Si ｂ ) S ｃ X ｄ Z ｅ ... (1) (In formula (1), X is a halogen element including at least one of bromine and iodine. Z is at least one element other than Li, P, Si, S, and X. a, b, c, d, and e satisfy the following relationships: 3.00≦a≦3.80, 0.12≦b<1.00, 3.00≦c≦4.20, 0.01≦d≦1.00, and 0≦e≦1.00, respectively.)

[0067] When the solid electrolyte has a composition represented by the above formula (1), the heat resistance and ionic conductivity are further improved. In the case of the solid electrolyte represented by the above formula (1), the molar ratio ((Br + I) / X) of the total content of bromine and iodine to the content of halogen elements is also 0.30 or more. The preferred ranges of a, b, c, d, and e in the above formula (1) are the same as the preferred ranges of the molar ratios of the content of each element to the total content of phosphorus and silicon. That is, the preferred range of a is the same as the preferred range of the molar ratio (Li / (P + Si)) described above, the preferred range of b is the same as the preferred range of the above-mentioned (Si / (P + Si)), the preferred range of c is the same as the preferred range of the above-mentioned (S / (P + Si)), the preferred range of d is the same as the preferred range of the above-mentioned (X / (P + Si)), and the preferred range of e is the same as the preferred range of the above-mentioned (Z / (P + Si)). The preferred ranges of other contents in the solid electrolyte represented by the above formula (1), such as the total content of bromine element and iodine element relative to the content of halogen elements, the content of bromine element, and the content of iodine element, are also the same as the preferred ranges described above.

[0068] (Crystal Structure) The solid electrolyte according to one embodiment of the present invention has a HICP crystal structure. That is, in an X-ray diffraction pattern using CuKα radiation, the solid electrolyte has diffraction peaks in the range of a diffraction angle 2θ of 20.0°±0.5° and in the range of a diffraction angle 2θ of 29.3°±0.5°. In addition, in the X-ray diffraction pattern of the solid electrolyte, there is no diffraction peak in the range of a diffraction angle 2θ of 17.5°±0.5°, or there is a diffraction peak in the range of a diffraction angle 2θ of 17.5°±0.5°, and the intensity (I Ｌ ) is the intensity of the diffraction peak in the range of the diffraction angle 2θ of 20.0°±0.5° (I Ｈ ) or less. As described above, a crystal structure having a diffraction peak in the range of a diffraction angle 2θ of 17.5°±0.5° in an X-ray diffraction pattern using CuKα radiation is considered to be the above-mentioned low ionic conductive phase (LICP). Since the solid electrolyte has a HICP crystal structure and does not have a LICP crystal structure or has a relatively small amount of LICP, it can have sufficient ionic conductivity.

[0069] The intensity of the diffraction peak in the range of the diffraction angle 2θ of 20.0°±0.5° in the X-ray diffraction pattern (I Ｈ ) the intensity of the diffraction peak in the range of the diffraction angle 2θ of 17.5°±0.5° (I Ｌ ) ratio (I Ｌ / I Ｈ The upper limit of the ratio (I) is 1 / 5, preferably 1 / 10, more preferably 1 / 50, even more preferably 1 / 100, and particularly preferably 0. When the diffraction angle 2θ does not have a diffraction peak in the range of 17.5°±0.5°, Ｌ / I Ｈ ) is 0.

[0070] The solid electrolyte may partially have other crystal structures. Examples of other crystal structures include β-Li ３ P.S. ４ , LGPS type, Argyrodite type, Li ７ P ３ S １１ , Thio-LISICON, etc. The solid electrolyte may have an amorphous portion.

[0071] (Physical Properties, Uses, etc.) The lower limit of the ionic conductivity at 25°C of the solid electrolyte according to one embodiment of the present invention is preferably 1.0 mS / cm, more preferably 2.0 mS / cm, even more preferably 2.5 mS / cm, and even more preferably 3.0 mS / cm, 3.5 mS / cm, 4.0 mS / cm, 4.5 mS / cm, 5.0 mS / cm, 5.5 mS / cm, or 6.0 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 an energy storage device including the solid electrolyte can be improved. The upper limit of the ionic conductivity is not particularly limited, but may be, for example, 20 mS / cm, 10 mS / cm, or 8 mS / cm.

[0072] The lower limit of the ionic conductivity at 25°C after the solid electrolyte is heat-treated at 270°C for 2 hours is preferably 1.0 mS / cm, more preferably 2.0 mS / cm, even more preferably 2.5 mS / cm, and even more preferably 3.0 mS / cm, 4.0 mS / cm, or 5.0 mS / cm. When the ionic conductivity at 25°C after the solid electrolyte is heat-treated at 270°C for 2 hours is equal to or higher than the lower limit, the solid electrolyte has higher heat resistance and is more highly productive. The upper limit of the ionic conductivity at 25°C after the solid electrolyte is heat-treated at 270°C for 2 hours is not particularly limited, and may be, for example, 20 mS / cm, 10 mS / cm, or 8 mS / cm.

[0073] 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 a non-aqueous electrolyte in a storage element such as a lithium ion secondary battery, particularly a lithium ion storage element. In particular, the solid electrolyte can be particularly suitably used as a non-aqueous electrolyte in an all-solid-state battery. The solid electrolyte can be used in any of a positive electrode, a separator, a negative electrode, or the like in a storage element.

[0074] <Material for Producing Solid Electrolyte> A material for producing a solid electrolyte according to one embodiment of the present invention contains lithium, phosphorus, silicon, sulfur, and a halogen, wherein the molar ratio (Si / (P+Si)) of the content of the silicon element to the total content of the phosphorus and the silicon element is 0.12 or more, the halogen element includes at least one of bromine and iodine, and the molar ratio ((Br+I) / X) of the total content of the bromine and iodine element to the content of the halogen element is 0.30 or more.

[0075] The material for producing a solid electrolyte is a material for producing a solid electrolyte according to one embodiment of the present invention. Specifically, the material for producing a solid electrolyte is heat-treated to obtain a solid electrolyte according to one embodiment of the present invention. The specific elemental composition and preferred elemental composition of the material for producing a solid electrolyte are the same as the specific elemental composition and preferred elemental composition of the solid electrolyte according to one embodiment of the present invention described above.

[0076] The material for producing a solid electrolyte is usually a mixture of two or more compounds or simple substances (hereinafter also referred to as compounds, etc.) containing at least one element from the group of elements consisting of lithium, phosphorus, silicon, sulfur, and halogens. Any of the compounds, etc. contained in the material for producing a solid electrolyte may contain lithium, phosphorus, silicon, sulfur, and halogens. One compound may contain two or more elements from the group of elements consisting of lithium, phosphorus, silicon, sulfur, and halogens. The material for producing a solid electrolyte may also contain a compound, etc. that does not contain any of lithium, phosphorus, silicon, sulfur, and halogens.

[0077] Examples of compounds containing lithium include Li ２ S., Li. ２ O, Li ３ N., Li. ２ CO ３ , metallic lithium, LiBr, LiI, etc. Among these, Li ２ S, LiBr and LiI are preferred. The lithium element-containing compounds may be used alone or in combination of two or more.

[0078] Examples of compounds containing phosphorus include P ２ S ３ , P ２ S ５ , P ２ O ５ , P ３ N ５ Among these, P ２ S ３ and P ２ S ５ is preferred, and P ２ S ５ The phosphorus-containing compound may be used alone or in combination of two or more.

[0079] Examples of compounds containing silicon include SiS, SiS ２ , SiO ２ Among these, SiS２ The silicon-containing compound may be used alone or in combination of two or more.

[0080] Examples of compounds containing sulfur include Li ２ S, P ２ S ３ , P ２ S ５ , Al ２ S ３ , MgS, SiS ２ , elemental sulfur, etc. Among these, Li ２ S, P ２ S ３ , P ２ S ５ and SiS ２ The sulfur-containing compounds may be used alone or in combination of two or more.

[0081] Examples of compounds containing halogen elements include LiBr, LiI, Br ２ , I ２ Among these, LiI and LiBr are preferred. The halogen-containing compounds may be used alone or in combination of two or more.

[0082] For example, in one embodiment, the material for producing a solid electrolyte is Li ２ S and P ２ S ５ and SiS ２ and a mixture of LiI and LiBr.

[0083] The material for producing a solid electrolyte may be a mixture of two or more compounds containing at least one element selected from the group of elements consisting of lithium, phosphorus, silicon, sulfur, and halogen elements, which has been subjected to a process such as mechanical milling.

[0084] Mechanical milling may be either dry or wet, but wet milling is preferred because it allows for more uniform mixing of raw material compounds, etc. Examples of mechanical milling include container-driven mills, media agitation mills, milling using high-speed rotary grinders, roller mills, jet mills, etc. Examples of container-driven mills include rotary mills, vibration mills, planetary mills, etc. Examples of media agitation mills include attritors, bead mills, etc. Examples of milling using high-speed rotary grinders include hammer mills, pin mills, etc. Among these, container-driven mills are preferred, and planetary mills are particularly preferred.

[0085] The material for producing a solid electrolyte that has been subjected to a process such as mechanical milling may have a crystalline structure, but is preferably a so-called sulfide glass. The term "sulfide glass" refers to a sulfide solid electrolyte that includes an amorphous structure. When the material for producing a solid electrolyte is sulfide glass, Li ２ A solid electrolyte can be obtained in which each element is highly dispersed and there is little crystalline phase of low stability such as S.

[0086] The material for producing a solid electrolyte according to one embodiment of the present invention has one or more crystallization temperatures in the range of 150°C or more and 400°C or less, and has an ionic conductivity σ at 25°C after being heat-treated for two hours at T1°C, which is the lowest temperature among the one or more crystallization temperatures. Ｔ１ Ionic conductivity σ at 25 ° C. after heat treatment at (T1 + 40) ° C. for 2 hours Ｔ１＋４０ The ratio of (σ Ｔ１＋４０ / σ Ｔ１ ) is 0.7 or more. Ｔ１＋４０ / σ Ｔ１ The lower limit of the ratio (σ) is preferably 0.9, more preferably 1.0. Ｔ１＋４０ / σ Ｔ１ When the ratio (σ) is equal to or greater than the lower limit, a solid electrolyte having sufficient ionic conductivity can be obtained even if the heat treatment is performed at a temperature somewhat higher than T1°C, which is the temperature at which HICP usually precipitates, and productivity is high. Ｔ１＋４０ / σ Ｔ１ The upper limit of the ratio may be, for example, 3.0, 2.0, 1.5, or 1.0.

[0087] A material for producing a solid electrolyte according to one embodiment of the present invention has multiple crystallization temperatures in the range of 150°C to 400°C. When the lowest crystallization temperature among the multiple crystallization temperatures is T1°C and the second lowest crystallization temperature among the multiple crystallization temperatures is T2°C, the difference (T2-T1) between the crystallization temperature T1 and the crystallization temperature T2 is preferably 50°C or more. The difference (T2-T1) is more preferably 70°C or more, even more preferably 80°C or more, and even more preferably 90°C or more or 100°C or more. As described above, the crystallization temperature T1 typically corresponds to the precipitation temperature of HICP. Furthermore, the crystallization temperature T2 refers to the precipitation temperature or phase transition temperature of LICP or other crystalline phases with low ionic conductivity. To further increase the ionic conductivity of the solid electrolyte, the heat treatment temperature is preferably controlled within a temperature range in which HICP precipitates and LICP or the like is unlikely to be generated. The larger the difference (T2-T1) between the crystallization temperature T1 and the crystallization temperature T2, the wider the temperature range in which the thermal stability of the HICP is high, and the more improved the productivity. The upper limit of the difference (T2-T1) may be, for example, 180°C, 160°C, or 140°C.

[0088] <Method for Producing a Solid Electrolyte> A method for producing a solid electrolyte according to one embodiment of the present invention comprises heat treating a material for producing a solid electrolyte. Specific and preferred embodiments of the material for producing a solid electrolyte are as described above for the material for producing a solid electrolyte according to one embodiment of the present invention.

[0089] In this production method, a solid electrolyte at least partly crystallized into HICP is obtained by subjecting a material for producing a solid electrolyte to a heat treatment. The heat treatment may be performed under a reduced pressure atmosphere or an inert gas atmosphere.

[0090] In the method for producing a solid electrolyte according to one embodiment of the present invention, the heat treatment may include a time period in which the temperature is maintained at, for example, (T1-10)°C or higher, based on the crystallization temperature T1. However, it is preferable to include a time period in which the temperature is maintained at T1°C or higher, and more preferably a time period in which the temperature is maintained at (T1+10)°C or higher. It may also include a time period in which the temperature is maintained at (T1+30)°C or higher or (T1+50)°C or higher. Specifically, the heat treatment may include a time period in which the temperature is maintained at 200°C or higher, 220°C or higher, or 240°C or higher. During the time period, the temperature is preferably maintained within a range of ±20°C from the target temperature, more preferably within a range of ±10°C, and even more preferably within a range of ±5°C. By including a time period in which the heat treatment is performed at the above temperatures, the precipitation of HICP can be promoted. The maximum temperature in the heat treatment is preferably (T2-20)°C or less, more preferably (T2-30)°C or less, and even more preferably (T2-40)°C or less, based on the crystallization temperature T2. Specifically, the maximum temperature in the heat treatment is preferably 400°C or less, more preferably 360°C or less, even more preferably 320°C or less, and may be 280°C or less. By setting the maximum temperature in the heat treatment as described above, it is possible to suppress a phase transition to LICP, etc. The time period may be, for example, 0.7 hours or more and 48 hours or less, 1.0 hours or more and 24 hours or less, 1.3 hours or more and 12 hours or less, 1.6 hours or more and 8 hours or less, or 2.0 hours or more and 4 hours or less.

[0091] The solid electrolyte obtained by the above-described method for producing a solid electrolyte is also one embodiment of the present invention.

[0092] <Electricity storage element> An electric storage element according to one embodiment of the present invention includes a positive electrode, a negative electrode, a separator, and a container that houses these. The separator is a layer that is interposed between the positive electrode and the negative electrode and electrically insulates the positive electrode from the negative electrode. A solid electrolyte, which is a non-aqueous electrolyte, is contained in at least one of the positive electrode, the negative electrode, and the separator. The electric storage element according to one embodiment of the present invention may be a secondary battery or an all-solid-state battery.

[0093] An energy storage element 1 shown in FIG. 1 , which is one embodiment of the present invention, is an all-solid-state battery, i.e., a secondary battery in which a positive electrode 2 and a negative electrode 3 are disposed with a separator 4 interposed therebetween. The positive electrode 2 includes a positive electrode substrate 5 and a positive electrode active material layer 6, with the positive electrode substrate 5 being the outermost layer of the positive electrode 2. The negative electrode 3 includes a negative electrode substrate 7 and a negative electrode active material layer 8, with the negative electrode substrate 7 being the outermost layer of the negative electrode 2. In the energy storage element 1 shown in FIG. 1 , the negative electrode active material layer 8, the separator 4, the positive electrode active material layer 6, and the positive electrode substrate 5 are stacked in this order on the negative electrode substrate 7. An intermediate layer may be provided between the positive electrode substrate 5 and the positive electrode active material layer 6. Similarly, an intermediate layer may be provided between the negative electrode substrate 7 and the negative electrode active material layer 8. The energy storage element according to one embodiment of the present invention may further include other components, such as a container. Other components, such as a container, are omitted from the energy storage element 1 shown in FIG. 1 .

[0094] The energy storage element 1 contains a solid electrolyte according to an embodiment of the present invention in at least one of the positive electrode 2, the negative electrode 3, and the separator 4. More specifically, the solid electrolyte according to an embodiment of the present invention is contained in at least one of the positive electrode active material layer 6, the negative electrode active material layer 8, and the separator 4. The energy storage element 1 contains a solid electrolyte with high heat resistance, and therefore has high productivity.

[0095] The energy storage element 1 may be configured to use a solid electrolyte other than the solid electrolyte according to one embodiment of the present invention. Examples of other solid electrolytes include sulfide solid electrolytes other than the solid electrolyte according to one embodiment of the present invention, oxide solid electrolytes, dry polymer electrolytes, gel polymer electrolytes, and pseudo-solid electrolytes, with sulfide solid electrolytes being preferred. The solid electrolyte may be a crystalline solid electrolyte or an amorphous solid electrolyte. A crystalline solid electrolyte refers to a solid electrolyte in which a peak derived from the solid electrolyte is observed in the X-ray diffraction pattern. An amorphous solid electrolyte refers to a solid electrolyte in which the X-ray diffraction pattern is a halo pattern in which substantially no peaks other than those derived from the raw materials are observed. Furthermore, a single layer in the energy storage element 1 may contain multiple different solid electrolytes, or each layer may contain a different solid electrolyte.

[0096] The sulfide solid electrolyte preferably contains at least sulfur element and further contains lithium element. The sulfide solid electrolyte preferably has lithium ion conductivity. The sulfide solid electrolyte preferably also contains phosphorus element and preferably further contains a halogen element. The sulfide solid electrolyte preferably contains at least one of bromine element and iodine element as the halogen element.

[0097] When the sulfide solid electrolyte is a crystalline solid electrolyte, its crystal structure may be an argyrodite crystal structure, Li ３ P.S. ４ Crystal structure, Li ４ P ２ S ６ Crystal structure, Li ７ P ３ S １１ Crystal structure, Li １０ GeP ２ S １２ Examples of the sulfide solid electrolyte include those having a crystalline structure such as a thio-lisicon type crystalline structure, an anti-fluorite type crystalline structure, and the like.

[0098] Examples of sulfide solid electrolytes other than the solid electrolyte according to one embodiment of the present invention include Li ２ S-P ２ S ５ , Li ２ S-P ２ S ５ - LiI, Li ２ S-P ２ S ５ -LiCl, Li ２ S-P ２ S ５ - LiBr, Li ２ S-P ２ S ５ -Li ２ O, Li ２ S-P ２ S ５ -Li ２ O-LiI, Li ２ S-P ２ S ５ -Li ３ N., Li. ２ S-SiS ２ , Li ２ S-SiS ２- LiI, Li ２ S-SiS ２ - LiBr, Li ２ S-SiS ２ -LiCl, Li ２ S-SiS ２ -B ２ S ３ - LiI, Li ２ S-SiS ２ -P ２ S ５ - LiI, Li ２ S-B ２ S ３ , Li ２ S-P ２ S ５ -Z ｍ S ２ｎ (where m and n are positive numbers, and Z is Ge, Zn, or Ga.), Li ２ S-GeS ２ , Li ２ S-SiS ２ -Li ３ P.O. ４ , Li ２ S-SiS ２ -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 GeP ２ S １２ etc.

[0099] The energy storage element according to one embodiment of the present invention may further include, for example, a positive electrode lead, a positive electrode external terminal, a negative electrode lead, and a negative electrode external terminal. The positive electrode lead and the negative electrode lead are housed in a container. The positive electrode external terminal and the negative electrode external terminal are provided outside the container. The positive electrode is electrically connected to the positive electrode external terminal via the positive electrode lead. The negative electrode is electrically connected to the negative electrode external terminal via the negative electrode lead.

[0100] Hereinafter, main components constituting an energy storage element according to one embodiment of the present invention will be described in detail, mainly in the case where the energy storage element is an all-solid-state battery, but this is not intended to limit the application of the present invention.

[0101] (Positive electrode) As described above, the positive electrode has a positive electrode substrate and a positive electrode active material layer laminated on the positive electrode substrate directly or via an intermediate layer. Usually, the positive electrode has a portion where the positive electrode substrate is exposed. This exposed portion of the positive electrode substrate is usually connected to the above-mentioned positive electrode lead. The positive electrode may have a shape such as a sheet, plate, or strip.

[0102] The thickness of the positive electrode is appropriately set depending on the application of the energy storage element. The average thickness of the positive electrode may be, for example, 30 μm or more and 1,000 μm or less. The lower limit of the average thickness of the positive electrode may be 50 μm, 100 μm, or 200 μm. The upper limit of the average thickness of the positive electrode may be 500 μm, 400 μm, 300 μm, 200 μm, or 100 μm. The average thickness of the positive electrode is the average thickness of the portion where the positive electrode active material layer is laminated directly or via an intermediate layer on the positive electrode substrate. In the case where both the portion where the positive electrode active material layer is laminated on both sides of the positive electrode substrate and the portion where the positive electrode active material layer is laminated on only one side of the positive electrode substrate exist, the average thickness of the portion where the positive electrode active material layer is laminated on both sides of the positive electrode substrate is taken as the average thickness. In addition, in this specification, "average thickness" means the average value of thicknesses measured at any five positions.

[0103] The positive electrode substrate has electrical conductivity. In this specification, "having electrical conductivity" means that the volume resistivity is 10 －２ The volume resistivity is a value measured in accordance with JIS-H-0505 (1975). On the other hand, in this specification, "not having electrical conductivity" or "having (electrical) insulation" means that the volume resistivity is 10 ７ It means that the resistance is Ω·cm or more.

[0104] Examples of materials for the positive electrode substrate include metals such as aluminum, titanium, iron, and alloys thereof (stainless steel, etc.). Among these, aluminum or an aluminum alloy is preferred from the viewpoints of potential resistance, high electronic conductivity, and cost.

[0105] The positive electrode substrate has a shape such as a sheet, plate, or strip. Examples of the positive electrode substrate include foil, vapor-deposited film, mesh, and porous material, and foil is preferred. The positive electrode substrate may be, for example, aluminum foil or aluminum alloy foil.

[0106] The average thickness of the positive electrode substrate may be, for example, 3 μm or more and 50 μm or less. The lower limit of the average thickness of the positive electrode substrate may be 5 μm, 8 μm, 10 μm, or 15 μm. The upper limit of the average thickness of the positive electrode substrate may be 40 μm, 30 μm, 20 μm, or 15 μm.

[0107] The intermediate layer is a layer disposed between the positive electrode substrate and the positive electrode active material layer. The intermediate layer contains, for example, a conductive agent and a binder. When the intermediate layer contains a conductive agent, the contact resistance between the positive electrode substrate and the positive electrode active material layer can be reduced. Examples of the conductive agent and binder used in the intermediate layer include the same conductive agent and binder used in the positive electrode active material layer described below.

[0108] The positive electrode active material layer includes a positive electrode active material. The positive electrode active material layer may include optional components such as a solid electrolyte, a conductive agent, a binder, a thickener, and a filler as needed. The positive electrode active material layer may be formed from a positive electrode mixture including a positive electrode active material and other optional components. When the positive electrode active material layer includes a solid electrolyte, the positive electrode active material layer may be formed by coating and drying a composition including the above-mentioned components and an organic solvent. As in the energy storage element 1 of FIG. 1, the positive electrode active material layer may be provided on only one side of a positive electrode substrate having a shape such as a sheet. In another embodiment, the positive electrode active material layer may be provided on both sides of the positive electrode substrate.

[0109] As the positive electrode active material, a known positive electrode active material can be used. A material capable of absorbing and releasing lithium ions is typically used as the positive electrode active material for a lithium ion secondary battery. Examples of the positive electrode active material include lithium transition metal composite oxides, polyanion compounds, chalcogen compounds, sulfur-based materials, and lithium oxide. One or more positive electrode active materials can be used.

[0110] Examples of the transition metal element contained in the lithium transition metal composite oxide include nickel, cobalt, and manganese. The lithium transition metal composite oxide may also contain a typical metal element such as aluminum. Examples of the lithium transition metal composite oxide include α-NaFeO ２ Examples of the lithium transition metal composite oxide include a lithium transition metal composite oxide having a crystalline structure and a lithium transition metal composite oxide having a spinel crystalline structure.

[0111] α-NaFeO ２ As the lithium transition metal composite oxide having a crystalline structure, Li １＋α Ma １－α O ２ (Ma is a metal element other than lithium containing one or more transition metal elements, where 0≦α<1.) Ma preferably contains one or more of Ni, Co, and Mn. The total content of Ni, Co, and Mn relative to Ma ((Ni+Co+Mn) / Ma) is preferably 90 mol% or more, and more preferably 98 mol% or more.

[0112] Examples of lithium transition metal composite oxides having a spinel crystal structure include Li β Mb ２ O ４ (Mb is a metal element other than lithium containing one or more transition metal elements, and β is 0<β≦1.2). Mb preferably contains Mn. The content of Mn relative to Mb (Mn / Mb) is preferably 50 mol % or more, and more preferably 80 mol % or more.

[0113] The polyanion compound is a compound composed of a polyanion (i.e., a polyvalent oxoacid anion) and a cation. The polyanion compound preferably contains a lithium cation and a transition metal cation as the cation. Examples of the polyanion compound include LiFePO ４ , LiMnPO ４ , LiMn ｘ Fe １－ｘ P.O. ４ (0<x<1), LiNiPO ４ , LiCoPO ４, Li ３ V ２ (P.O. ４ ) ３ , Li ２ MnSiO ４ , Li ２ CoPO ４ The surfaces of the particles of the polyanionic compound may be coated with other materials (for example, carbon materials described below).

[0114] Examples of the chalcogen compound include titanium disulfide, molybdenum disulfide, and molybdenum dioxide.

[0115] Examples of sulfur-based materials include elemental sulfur, metal sulfides such as lithium sulfide, organic disulfide compounds, and organic sulfur compounds such as carbon sulfide compounds.

[0116] The atoms or polyanions in these materials serving as the positive electrode active material may be partially substituted with atoms or anion species of other elements, and the surfaces of these materials may be coated with other materials.

[0117] The positive electrode active material is usually particulate. 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-mentioned lower limit or more, the production and handling of the positive electrode active material becomes easier. By setting the average particle size of the positive electrode active material to the above-mentioned upper limit or less, the electronic conductivity of the positive electrode active material layer is improved. When a composite of the positive electrode active material and another material is used, the average particle size of the composite is taken as the average particle size of the positive electrode active material. The term "average particle size" refers to the value (D50) 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 by laser diffraction / scattering in accordance with JIS-Z-8825 (2013) for a diluted solution obtained by diluting particles with a solvent. For example, known methods using a pulverizer, a classifier, or the like can be used to obtain particles of the positive electrode active material and the negative electrode active material described below with a predetermined particle size.

[0118] The content of the positive electrode active material in the positive electrode active material layer is preferably 50% by mass or more and 99% by mass or less, more preferably 70% by mass or more and 98% by mass or less, and may be 80% by mass or more and 95% by mass or less. By setting the content of the positive electrode active material within the above range, both high energy density and manufacturability of the positive electrode active material layer can be achieved.

[0119] In the positive electrode active material layer, the solid electrolyte may form a composite with the positive electrode active material. Such a composite may further contain other components (e.g., a conductive agent) in addition to the solid electrolyte and the positive electrode active material.

[0120] When the positive electrode active material layer contains a solid electrolyte, the content of the solid electrolyte in the positive electrode active material layer is preferably 5% by mass or more and 50% by mass or less, may be 10% by mass or more and 40% by mass or less, or may be 15% by mass or more and 30% by mass or less.

[0121] When the solid electrolyte according to one embodiment of the present invention is used in the positive electrode active material layer, 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 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.

[0122] The conductive agent is usually a component made of a material having electrical conductivity. Even when the volume resistivity of the conductive agent cannot be measured directly, it is possible to measure the volume resistivity by measuring the volume resistivity of the conductive agent when the volume resistivity is 10 －２Conductive agents are materials known to have a resistivity of Ω·cm or less. Examples of conductive agents include carbon materials, metals, and conductive ceramics. Carbon materials are materials whose primary constituent element is carbon. The primary constituent element refers to the element with the highest content by mass. For example, the carbon content in the carbon material may be 80% by mass or more, 90% by mass or more, 95% by mass, 99% by mass, or 99.9% by mass or more. The carbon material is preferably a carbon material other than an uncarbonized polymer compound. Examples of carbon materials include graphite, non-graphitic carbon, and graphene-based carbon. Examples of non-graphitic 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 a powder or fiber. The conductive agent may be one or more kinds. The conductive agent may be a composite of these materials. For example, a composite material of carbon black and CNT may be used.

[0123] The content of the conductive agent in the positive electrode active material layer is preferably 0.1% by mass to 10% by mass, more preferably 1% by mass to 9% by mass, and even more preferably 3% by mass to 8% by mass. The upper limit of the content of the conductive agent may be 5%, 4%, or 3% by mass. By setting the content of the conductive agent within the above range, it is possible to increase the energy density of the energy storage element, etc.

[0124] Examples of the binder include a water-based binder and an organic solvent-based binder.

[0125] The aqueous binder is a binder that dissolves or disperses in water. The aqueous binder may be a binder that dissolves or disperses 1 part by mass or more in 100 parts by mass of water at 20° C. Examples of aqueous binders include polyethylene oxide, polypropylene oxide, polyvinyl alcohol, polyacrylic acid, polymethacrylic acid, polytetrafluoroethylene, styrene-butadiene rubber, polyethylene, polypropylene, nitrile-butadiene rubber, and cellulose.

[0126] The organic solvent-based binder is a binder that dissolves or disperses in an organic solvent. The organic solvent-based binder may be a binder that dissolves or disperses at 1 part by mass or more in 100 parts by mass of an organic solvent at 20°C. When a positive electrode active material layer is formed using a positive electrode mixture paste whose dispersion medium is an organic solvent or a mixed solvent mainly containing an organic solvent, an organic solvent-based binder (a polymer material that is soluble or dispersible in an organic solvent) can be used. Examples of organic solvent-based binders include polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, a copolymer of ethylene and vinyl alcohol, polyacrylonitrile, polyphosphazene, polysiloxane, polyvinyl acetate, polymethyl methacrylate, polystyrene, polycarbonate, polyamide, polyimide, polyamideimide, a crosslinked polymer of cellulose and chitosan pyrrolidone carboxylate, and chitosan derivatives.

[0127] The binder may be a fluororesin (polytetrafluoroethylene, polyvinylidene fluoride, etc.), a polyolefin (polyethylene, polypropylene, etc.), an elastomer (ethylene propylene diene rubber, styrene butadiene rubber, fluororubber, etc.), a polysaccharide polymer (cellulose, chitosan derivatives, etc.), etc. One or more types of binders can be used.

[0128] The content of the binder in the positive electrode active material layer is preferably 0.1% by mass to 10% by mass, more preferably 1% by mass to 9% by mass, and more preferably 3% by mass to 8% by mass. The upper limit of the binder content may be 5%, 4%, or 3% by mass. By setting the binder content within the above range, it is possible to stably hold the positive electrode active material. The technology disclosed herein can also be implemented in an embodiment in which the positive electrode active material layer does not contain a binder.

[0129] Examples of thickeners include polysaccharide polymers such as carboxymethyl cellulose and methyl cellulose. When the thickener has a functional group that reacts with lithium or the like, the functional group may be deactivated in advance by methylation or the like. The thickener may function as a binder. One or more types of thickeners may be used. When the positive electrode active material layer contains a thickener, the content of the thickener in the positive electrode active material layer is preferably 0.1% by mass or more and 8% by mass or less, more preferably 5% by mass or less, and even more preferably 2% by mass or less. The technology disclosed herein may also be implemented in an embodiment in which the positive electrode active material layer does not contain a thickener.

[0130] The filler is not particularly limited. The filler may be a component other than the positive electrode active material, solid electrolyte, conductive agent, binder, and thickener, and may be intentionally added. The filler may be added to fill gaps in the positive electrode active material layer, or may be added for other purposes. The filler may be an organic substance such as polyolefin, or an inorganic substance such as an inorganic oxide, hydroxide, or carbonate. One or more fillers may be used. When the positive electrode active material layer contains a filler, the content of the filler in the positive electrode active material layer may be 0.1% by mass or more and 8% by mass or less, typically 5% by mass or less is preferred, and 2% by mass or less is more preferred. The technology disclosed herein may also be implemented in an embodiment in which the positive electrode active material layer does not contain a filler.

[0131] The positive electrode active material layer may further contain other components in addition to the positive electrode active material, solid electrolyte, conductive agent, binder, thickener, and filler. These other components include those unintentionally generated in the positive electrode active material layer. The positive electrode active material layer may also contain unintentionally contained impurities as the other components, as long as the effects of the present invention are achieved. The upper limit of the content of the other components in the positive electrode active material layer may be 10% by mass, 5%, 2%, 1%, 0.1%, or 0.01% by mass. The upper limit of the content of the unintentionally generated components in the positive electrode active material layer may be 10% by mass, 5%, 2%, 1%, 0.1%, or 0.01% by mass. The upper limit of the content of the unintentionally contained impurities in the positive electrode active material layer may be 10% by mass, 5%, 2%, 1%, 0.1%, or 0.01% by mass.

[0132] The thickness of the positive electrode active material layer is appropriately set depending on the type of positive electrode active material, the application of the energy storage device, and the like. The average thickness of one positive electrode active material layer may be, for example, 5 μm or more and 1,000 μm or less. The lower limit of the average thickness of one positive electrode active material layer may be 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, or 100 μm. The upper limit of the average thickness of one positive electrode active material layer may be 800 μm, 500 μm, 200 μm, 100 μm, 80 μm, 60 μm, or 40 μm. The mass per unit area of ​​one positive electrode active material layer is, for example, 4 mg / cm. ２ 100mg / cm or more ２ The lower limit of the mass per unit area of ​​one positive electrode active material layer may be 6 mg / cm or less. ２ , 8 mg / cm ２ or 10 mg / cm ２ The upper limit of the mass per unit area of ​​one positive electrode active material layer is 50 mg / cm ２ , 20 mg / cm ２ , 15 mg / cm ２ , 12 mg / cm ２ or 10 mg / cm ２ may be.

[0133] (Negative electrode) As described above, the negative electrode has a negative electrode substrate and a negative electrode active material layer laminated on the negative electrode substrate directly or via an intermediate layer. Usually, the negative electrode has a portion where the negative electrode substrate is exposed. This portion where the negative electrode substrate is exposed is usually connected to the above-mentioned negative electrode lead. The negative electrode may have a shape such as a sheet, plate, or strip.

[0134] The thickness of the negative electrode is appropriately set depending on the application of the energy storage element, etc. The average thickness of the negative electrode may be, for example, 30 μm or more and 1,000 μm or less. The lower limit of the average thickness of the negative electrode may be 50 μm, 100 μm, or 200 μm. The upper limit of the average thickness of the negative electrode may be 500 μm, 400 μm, 300 μm, 200 μm, or 100 μm. The average thickness of the negative electrode is the average thickness of a portion where the negative electrode active material layer is laminated on the negative electrode substrate directly or via an intermediate layer. When there are both a portion where the negative electrode active material layer is laminated on both sides of the negative electrode substrate and a portion where the negative electrode active material layer is laminated on only one side of the negative electrode substrate, the average thickness of the portion where the negative electrode active material layer is laminated on both sides of the negative electrode substrate is taken as the average thickness.

[0135] The negative electrode substrate is conductive. Examples of materials for the negative electrode substrate include metals such as copper, nickel, iron, and alloys thereof (e.g., stainless steel), and carbon materials. Among these, copper or copper alloys are preferred.

[0136] The negative electrode substrate has a shape such as a sheet, plate, or strip. Examples of the form of the negative electrode substrate include foil, vapor-deposited film, mesh, and porous material, and foil is preferred. The negative electrode substrate may be, for example, copper foil or copper alloy foil.

[0137] The average thickness of the negative electrode substrate may be, for example, 2 μm or more and 35 μm or less. The lower limit of the average thickness of the negative electrode substrate may be 3 μm, 4 μm, 5 μm, or 10 μm. The upper limit of the average thickness of the negative electrode substrate may be 30 μm, 20 μm, 15 μm, or 10 μm.

[0138] The structure of the intermediate layer of the negative electrode is not particularly limited, and can be selected from the structures exemplified for the intermediate layer of the positive electrode, for example.

[0139] The negative electrode active material layer includes a negative electrode active material. The negative electrode active material layer may optionally include optional components such as a solid electrolyte, a conductive agent, a binder, a thickener, and a filler. The optional components such as the solid electrolyte, the conductive agent, the binder, the thickener, and the filler may be selected from the materials exemplified for the positive electrode. The negative electrode active material layer may be formed from a negative electrode mixture including a negative electrode active material and other optional components. When the negative electrode active material layer includes a solid electrolyte, the negative electrode active material layer may be formed by coating and drying a composition including the above-mentioned components and an organic solvent. As in the energy storage element 1 of FIG. 1, the negative electrode active material layer may be provided on only one side of a negative electrode substrate having a shape such as a sheet. In another embodiment, the negative electrode active material layer may be provided on both sides of the negative electrode substrate.

[0140] As the negative electrode active material, a known negative electrode active material can be used. A material capable of absorbing and releasing lithium ions is usually used as the negative electrode active material for a lithium ion secondary battery. Examples of the negative electrode active material include metallic lithium; metals or semimetals such as silicon and tin; metal oxides or semimetal oxides such as silicon oxide, titanium oxide, and tin oxide; Li ４ Ti ５ O １２ , LiTiO ２、 TiNb ２ O ７ Examples of the negative electrode active material include titanium-containing oxides such as those mentioned above; polyphosphate compounds; silicon carbide; and carbon materials such as graphite and non-graphitic carbon. The surface of the graphite may be coated with another material such as non-graphitic carbon. One or more negative electrode active materials may be used.

[0141] "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.

[0142] "Non-graphitic carbon" refers to a carbon material that has an average lattice spacing (d ００２) is 0.34 nm or more and 0.42 nm or less. Non-graphitizable carbon includes non-graphitizable carbon and graphitizable carbon. "Non-graphitizable carbon" refers to a carbon material having the above d ００２ The term "easily graphitizable carbon" refers to a carbon material having a particle size of 0.36 nm or more and 0.42 nm or less. ００２ The term "carbon material" refers to a carbon material having a particle size of 0.34 nm or more and less than 0.36 nm.

[0143] Here, the "discharged state" of the carbon material refers to a state in which the carbon material, which is the negative electrode active material, is discharged so that lithium ions that can be absorbed and released during charging and discharging are sufficiently released from the carbon material. For example, this refers to a state in which the open circuit voltage of a half cell using a negative electrode containing a carbon material as the negative electrode active material as the working electrode and metallic lithium as the counter electrode is 0.7 V or higher.

[0144] The negative electrode active material may be particulate. The average particle size of the negative electrode active material may be, for example, 1 nm or more and 100 μm or less. When the negative electrode active material is a carbon material, a titanium-containing oxide, a polyphosphate compound, or the like, the average particle size may be 1 μm or more and 100 μm or less. When the negative electrode active material is Si, Sn, Si oxide, Sn oxide, or the like, the average particle size may 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 or 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 negative electrode active material layer is improved.

[0145] The content of the negative electrode active material in the negative electrode active material layer is, for example, preferably 60% by mass to 99% by mass, more preferably 90% by mass to 98% by mass. By setting the content of the negative electrode active material within this range, both high energy density and manufacturability of the negative electrode active material layer can be achieved.

[0146] When the negative electrode active material is a metal such as metallic lithium, the negative electrode active material layer may be in the form of a foil. The metallic lithium may exist as pure metallic lithium consisting essentially of elemental lithium, or may exist as a lithium alloy containing other metal elements. When the negative electrode active material is a metal such as metallic lithium, the content of elemental lithium in the negative electrode active material layer may be 90% by mass or more, 99% by mass or more, or even 100% by mass.

[0147] When the negative electrode active material layer contains a conductive agent, the content of the conductive agent in the negative electrode active material layer 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. The content of the conductive agent in the negative electrode active material layer may be 5% by mass or less, or may be 2% by mass or less. The technology disclosed herein may also be implemented in an embodiment in which the negative electrode active material layer does not contain a conductive agent.

[0148] When the negative electrode active material layer contains a solid electrolyte, the content of the solid electrolyte is preferably 5% by mass or more and 90% by mass or less, may be 10% by mass or more and 70% by mass or less, or may be 20% by mass or more and 50% by mass or less.

[0149] When the solid electrolyte according to one embodiment of the present invention is used in the negative electrode active material layer, 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 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.

[0150] When the negative electrode active material layer contains a binder, the content of the binder in the negative electrode active material layer is preferably 0.1 mass% to 10 mass%, more preferably 0.5 mass% to 8 mass%. The content of the binder in the negative electrode active material layer may be 5 mass% or less, or may be 2 mass% or less. The technology disclosed herein may also be implemented in an embodiment in which the negative electrode active material layer does not contain a binder.

[0151] When the negative electrode active material layer contains a thickener, the content of the thickener in the negative electrode active material layer is preferably 0.1% by mass or more and 10% by mass or less, and more preferably 0.5% by mass or more and 8% by mass or less. The content of the thickener in the negative electrode active material layer may be 5% by mass or less, or may be 2% by mass or less. The technology disclosed herein may also be implemented in an embodiment in which the negative electrode active material layer does not contain a thickener.

[0152] The filler in the negative electrode active material layer may be a component other than the negative electrode active material, solid electrolyte, conductive agent, binder, and thickener, and may be an intentionally contained component. The filler may be contained as a component to fill gaps in the negative electrode active material layer, or may be contained for another purpose. When the negative electrode active material layer contains a filler, the content of the filler in the negative electrode active material layer may be 0.1% by mass or more and 8% by mass or less, and typically 5% by mass or less is preferred, and 2% by mass or less is more preferred. The technology disclosed herein may also be implemented in an embodiment in which the negative electrode active material layer does not contain a filler.

[0153] The negative electrode active material layer may further contain other components in addition to the negative electrode active material, solid electrolyte, conductive agent, binder, thickener, and filler. These other components include those unintentionally present in the negative electrode active material layer. The negative electrode active material layer may also contain unintentionally present impurities as other components, as long as the effects of the present invention are achieved. The upper limit of the content of the other components in the negative electrode active material layer may be 10% by mass, 5%, 2%, 1%, 0.1%, or 0.01% by mass. The upper limit of the content of the unintentionally present components in the negative electrode active material layer may be 10% by mass, 5%, 2%, 1%, 0.1%, or 0.01% by mass. The upper limit of the content of the unintentionally present impurities in the negative electrode active material layer may be 10% by mass, 5%, 2%, 1%, 0.1%, or 0.01% by mass.

[0154] The thickness of the negative electrode active material layer is appropriately set depending on the type of negative electrode active material, the application of the energy storage device, and the like. The average thickness of one negative electrode active material layer may be, for example, 5 μm or more and 1,000 μm or less. The lower limit of the average thickness of one negative electrode active material layer may be 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, or 100 μm. The upper limit of the average thickness of one negative electrode active material layer may be 800 μm, 500 μm, 200 μm, 100 μm, 80 μm, 60 μm, or 40 μm. The mass per unit area of ​​one negative electrode active material layer is, for example, 2 mg / cm. ２ 50mg / cm or more ２ The lower limit of the mass per unit area of ​​one negative electrode active material layer may be 3 mg / cm or less. ２ , 4 mg / cm ２ , 5 mg / cm ２ or 6 mg / cm ２ The upper limit of the mass per unit area of ​​one negative electrode active material layer is 30 mg / cm ２ , 20 mg / cm ２ , 15 mg / cm ２ , 12 mg / cm ２ or 10 mg / cm ２ may be.

[0155] (Isolation Layer) The isolation layer usually contains a solid electrolyte. The content of the solid electrolyte in the isolation layer is preferably 70% by mass or more and 100% by mass or less. The content of the solid electrolyte in the isolation layer may be 90% by mass or more, 99% by mass or more, or 100% by mass.

[0156] When the solid electrolyte according to one embodiment of the present invention is used in the separator layer, the content of the solid electrolyte according to one embodiment of the present invention relative to the total solid electrolyte in the separator layer 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.

[0157] The isolation layer may contain an additive (e.g., Li ３ P.O. ４The separator layer may contain optional components such as a phosphate compound, an oxide, a halogen compound, etc.), a binder, a thickener, a filler, etc. The optional components such as the binder, the thickener, the filler, etc. can be selected from the materials exemplified for the positive electrode active material layer. When the separator layer contains a solid electrolyte and a binder, the separator layer may be formed by coating and drying a composition containing the above-mentioned components and an organic solvent.

[0158] The average thickness of the separator is preferably 1 μm or more and 100 μm or less, more preferably 2 μm or more and 50 μm or less, and even more preferably 3 μm or more and 20 μm or less. By setting the average thickness of the separator to be equal to or greater than the lower limit, it is possible to insulate the positive electrode and the negative electrode with high reliability. By setting the average thickness of the separator to be equal to or less than the upper limit, it is possible to increase the energy density of the energy storage element.

[0159] (Container) The container accommodates the positive electrode, negative electrode, etc. in its internal space. Materials for the container include metal materials such as aluminum and stainless steel, and resin materials, with metal materials being preferred from the viewpoint of strength, etc. Composite materials of metal materials and resin materials can also be used.

[0160] The shape of the container is not particularly limited, and may be cylindrical, rectangular (square), disk-like, etc. The container may also be in the shape of a sheet formed from a metal-resin composite film.

[0161] (Shape, Use, etc. of Energy Storage Element) The shape of the energy storage element according to one embodiment of the present invention is not particularly limited. The energy storage element may be, for example, a cylindrical battery, a prismatic battery, a flat battery, a coin battery, a button battery, or the like.

[0162] The use of the energy storage element according to one embodiment of the present invention is not particularly limited, and the energy storage element can be used, for example, as a power source for automobiles such as electric vehicles, hybrid vehicles, and plug-in hybrid vehicles, a power source for electronic devices such as personal computers and communication terminals, a power source for power storage, and the like.

[0163] The energy storage element according to one embodiment of the present invention may be used singly or in multiples. When the required output and the required voltage are small, the energy storage element may be used singly. On the other hand, when at least one of the required output and the required voltage is large, the energy storage element may be used as an energy storage device combined with other energy storage elements. In an energy storage device in which multiple energy storage elements are combined, at least one of the energy storage elements included in the energy storage device may be the energy storage element according to one embodiment of the present invention. The energy storage device will be described in detail later.

[0164] In an energy storage element according to one embodiment of the present invention, for example, the container may be constrained so as to maintain a constant thickness, or may not be constrained in this manner. Furthermore, the container may be constrained so as to apply a constant load to the container. When the container is constrained, expansion of the container due to charge / discharge cycles, etc., may be suppressed, and deterioration of charge / discharge performance may be suppressed. When the container is constrained, a load may or may not be applied to the positive and negative electrodes in the container. For example, a constraining member that performs such constraining may be provided in the energy storage element or the energy storage device.

[0165] <Method for manufacturing energy storage element> The energy storage element according to one embodiment of the present invention can be manufactured by a known method, for example, the method for manufacturing the energy storage element includes preparing a positive electrode mixture, preparing a separator material, preparing a negative electrode mixture, and stacking the positive electrode, the separator, and the negative electrode.

[0166] Preparing a positive electrode mixture may mean producing a positive electrode mixture. The method for preparing the positive electrode mixture is not particularly limited and can be appropriately selected depending on the purpose. For example, the positive electrode mixture can be prepared by mixing a positive electrode active material and a solid electrolyte using a mechanical milling method or the like. It is also possible to produce a composite of a positive electrode active material and a solid electrolyte in advance, and then mix the obtained composite with other components.

[0167] Preparing an isolation layer material may mean producing an isolation layer material. A solid electrolyte as an isolation layer material can be produced by a conventionally known method. For example, it can be obtained by treating a predetermined material by mechanical milling. The isolation layer material may also be produced by heating a predetermined material to a melting temperature or higher by melt-quenching, melt-mixing the two at a predetermined ratio, and then quenching. Other methods for producing an 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), or a method in which the material is sintered in an argon atmosphere after treatment by mechanical milling.

[0168] Preparing the negative electrode mixture may be preparing a negative electrode mixture. The specific method for preparing the negative electrode mixture is the same as that for the positive electrode mixture. When a metal such as metallic lithium is used as the negative electrode active material, a metal foil that will become the negative electrode active material layer may be prepared instead of preparing the negative electrode mixture.

[0169] By stacking a positive electrode, a separator, and a negative electrode, for example, a positive electrode having a positive electrode substrate and a positive electrode active material layer, a separator, and a negative electrode having a negative electrode substrate and a negative electrode active material layer are stacked. In this process, the positive electrode, the separator, and the negative electrode may be formed sequentially in this order, or vice versa; the order of forming each layer is not particularly important. For example, the positive electrode is formed by pressure molding a positive electrode substrate and a positive electrode mixture, the separator is formed by pressure molding an separator material, and the negative electrode is formed by pressure molding a negative electrode substrate and a negative electrode mixture. The positive electrode, the separator, and the negative electrode may be stacked by pressure molding the positive electrode substrate, the positive electrode mixture, the separator material, the negative electrode mixture, and the negative electrode substrate all at once. The positive electrode and the negative electrode may be formed in advance, and then pressure molded and stacked with the separator. The positive electrode active material layer may be formed by coating and drying a paste-like positive electrode mixture. Similarly, the separator layer may be provided by applying and drying a paste of separator-forming material, and the negative electrode active material layer may be provided by applying and drying a paste of negative electrode mixture.

[0170] When the positive electrode active material layer, separator layer, and negative electrode active material layer contain a solid electrolyte, examples of organic solvents used in forming the positive electrode active material layer, separator layer, and negative electrode active material layer include aliphatic hydrocarbons (hexane, heptane, octane, decane, dodecane, etc.), alicyclic hydrocarbons (cyclohexane, cycloheptane, cyclooctane, cyclodecane, etc.), aromatic hydrocarbons (toluene, xylene, mesitylene, naphthalene, tetralin, etc.), ketones (3-pentanone, 4-heptanone, methylhexyl ketone, diisobutyl ketone, etc.), esters (butyl acetate, butyl butyrate, methyl butanoate, butyl pentanoate, butyl hexanoate, pentyl butyrate, pentyl pentanoate, pentyl hexanoate, hexyl butyrate, hexyl pentanoate, hexyl hexanoate, etc.), and ethers (dibutyl ether, tetrahydrofuran, anisole, etc.). One or more organic solvents can be used. The organic solvent is preferably a non-polar solvent. The non-polar solvent preferably has a dielectric constant of less than 5. By using such an organic solvent, it is possible to suppress the reaction between the organic solvent and the solid electrolyte.

[0171] 2 includes a plurality of energy storage units 20. Each energy storage unit 20 includes a plurality of electrically connected energy storage elements 1. The energy storage device 30 may include a bus bar (not shown) that electrically connects the plurality of energy storage elements 1, a bus bar (not shown) that electrically connects the plurality of energy storage units 20, and the like. The energy storage unit 20 or the energy storage device 30 may include a state monitoring device (not shown) that monitors the state of one or more energy storage elements 1.

[0172] <Other Embodiments> The solid electrolyte, material for producing a solid electrolyte, method for producing a solid electrolyte, and energy storage device of the present invention are not limited to the above-described embodiments, and various modifications may be made without departing from the spirit of the present invention. For example, the configuration of one embodiment can be added to the configuration of another embodiment, and part of the configuration of one embodiment can be replaced with the configuration of another embodiment or well-known technology. Furthermore, part of the configuration of one embodiment can be deleted. Also, well-known technology can be added to the configuration of one embodiment.

[0173] In the above embodiment, the electric storage element is used as a chargeable and dischargeable secondary battery, but the electric storage element may be of any type, shape, size, capacity, etc. The present invention can also be applied to various secondary batteries, electric double layer capacitors, lithium ion capacitors, and other capacitors.

[0174] For example, the energy storage element according to the present invention may include layers other than the positive electrode, separator, and negative electrode. The present invention can also be applied to an energy storage element including a bipolar electrode. The energy storage element according to the present invention may also include a liquid. Examples of such an energy storage element include an energy storage element in which voids in the positive electrode active material layer 6, separator 4, negative electrode active material layer 8, etc. in the above-described energy storage element 1 are filled with a nonaqueous electrolyte solution containing an ionic liquid or the like.

[0175] 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.

[0176] In the following examples and comparative examples, the solid electrolytes of each example represented by, for example, Example 1-X (X is 1, 2, 3, or 4) mean those obtained using the same material for producing a solid electrolyte. These are also collectively referred to as the material for producing a solid electrolyte or the solid electrolyte of Example 1. The same applies to Example 2, etc.

[0177] [Examples 1-1 to 1-4] Li was added to a glove box in an argon atmosphere with a dew point of −50° C. or less. ２ S (99.98%, Aldrich), P ２ S ５ (99%, manufactured by Aldrich), SiS ２(99%, manufactured by Materion), LiBr (99.999%, manufactured by Aldrich), and LiI (99.999%, manufactured by Aldrich) were weighed to a molar ratio of 58.25:16.50:5.83:11.65:7.77, and then mixed in a mortar to prepare a mixture containing lithium, phosphorus, silicon, sulfur, bromine, and iodine as constituent elements. The mixture was placed in a sealed 80 mL zirconia pot containing 160 g of zirconia balls with a diameter of 4 mm. Mechanical milling was performed for 45 hours at an orbital rotation speed of 510 rpm using a planetary ball mill (manufactured by FRITSCH, model number Premium line PL-7), and a material for producing a solid electrolyte was obtained. A portion of the obtained material for producing a solid electrolyte was taken out and subjected to DSC measurement by the method described above to determine the crystallization temperature T1 and the crystallization temperature T2. The results are shown in Table 1. The material for producing a solid electrolyte was subjected to a heat treatment in which it was held for 2 hours at a heat treatment temperature HT of 205°C (Example 1-1), 230°C (Example 1-2), 250°C (Example 1-3), or 270°C (Example 1-4), to obtain each of the solid electrolytes of Examples 1-1 to 1-4.

[0178] [Examples 2-1 to 21-2, Comparative Examples 1-1 to 6-2] The compounds used as raw materials and their amounts (molar ratios) were adjusted to obtain the composition ratios of the solid electrolytes as shown in Tables 1 to 3. The heat treatment temperatures HT were set as shown in Tables 1 to 3. Except for these points, the solid electrolytes of Examples 2-1 to 21-2 and Comparative Examples 1-1 to 6-2 were obtained in the same manner as in Example 1-1, etc. Furthermore, similar to Example 1-1, etc., a portion of the material for producing the solid electrolyte was taken out and subjected to DSC measurement using the method described above to determine the crystallization temperature T1 and the crystallization temperature T2. The results are shown in Tables 1 to 3. The results of Examples 2-1 to 2-4 are shown in both Tables 1 and 2 for comparison with other Examples, etc. Furthermore, Examples 2-1 and 2-4 are also shown in Table 3 for comparison with other Examples, etc. In Examples 17-1 to 21-2 and Comparative Examples 5-1 to 6-2, elemental chlorine was incorporated using LiCl (99.999%, manufactured by Aldrich).

[0179] With respect to the constituent elements of each solid electrolyte of the Examples and Comparative Examples, the molar ratio of the lithium content to the total content of phosphorus and silicon (Li / (P+Si)), the molar ratio of the sulfur content to the total content of phosphorus and silicon (S / (P+Si)), the molar ratio of the bromine content to the total content of phosphorus and silicon (Br / (P+Si)), the molar ratio of the iodine content to the total content of phosphorus and silicon (I / (P+Si)), the molar ratio of the phosphorus content to the total content of phosphorus and silicon (P / (P+Si)), and the molar ratio of the silicon content to the total content of phosphorus and silicon (Si / (P+Si)) are shown in Tables 1 to 3. Table 3 also shows the molar ratio of the total content of bromine and iodine to the halogen content in the solid electrolyte of each Example and Comparative Example ((Br+I) / X). It is to be noted that each solid electrolyte of the examples and comparative examples is considered to contain substantially no elements other than lithium, phosphorus, silicon, sulfur, bromine, and iodine. That is, for example, the composition formula of the solid electrolyte of Example 1-1 is Li ３．５０ (P ０．８５ Si ０．１５ ) S ３．９３ Br ０．３０ I ０．２０ is.

[0180] (DSC Curves) FIG. 3 shows DSC curves for the materials for producing a solid electrolyte of Comparative Example 1 (Si / (P+Si)=0), Comparative Example 2 (Si / (P+Si)=0.025), Comparative Example 3 (Si / (P+Si)=0.10), Example 2 (Si / (P+Si)=0.20), Example 3 (Si / (P+Si)=0.30), Example 4 (Si / (P+Si)=0.40), Example 5 (Si / (P+Si)=0.50), and Example 6 (Si / (P+Si)=0.60).

[0181] (X-ray Diffraction Measurement) Powder X-ray diffraction measurement was performed on each of the solid electrolytes of the Examples and Comparative Examples using the method described above, and X-ray diffraction patterns were obtained. Figure 4 shows X-ray diffraction patterns for the solid electrolytes of Comparative Example 1-1 (Si / (P+Si) = 0), Comparative Example 2-1 (Si / (P+Si) = 0.025), Comparative Example 3-1 (Si / (P+Si) = 0.10), Example 2-1 (Si / (P+Si) = 0.20), Example 3-1 (Si / (P+Si) = 0.30), Example 4-1 (Si / (P+Si) = 0.40), Example 5-1 (Si / (P+Si) = 0.50), and Example 6-1 (Si / (P+Si) = 0.60). These solid electrolytes were obtained by heat treatment at temperatures near the crystallization temperature T1°C of the solid electrolyte manufacturing materials used in each example. FIG. 5 shows X-ray diffraction patterns of the solid electrolytes of Comparative Example 3-4 (Si / (P+Si)=0.10), Example 2-4 (Si / (P+Si)=0.20), Example 3-3 (Si / (P+Si)=0.30), and Example 4-3 (Si / (P+Si)=0.40). These are solid electrolytes obtained by heat treatment at 270°C. FIG. 6 shows X-ray diffraction patterns of the solid electrolytes of Example 8-1 (Li / (P+Si)=3.20), Example 9-1 (Li / (P+Si)=3.30), Example 10-1 (Li / (P+Si)=3.40), Example 2-1 (Li / (P+Si)=3.50), and Example 11-1 (Li / (P+Si)=3.60). These are solid electrolytes obtained by heat treatment at temperatures near the crystallization temperature T1°C of the solid electrolyte manufacturing materials used in each example. 7 shows X-ray diffraction patterns of the solid electrolytes of Example 2-1 ((Br + I) / X = 1.00), Example 17-1 ((Br + I) / X = 0.88), Example 18-1 ((Br + I) / X = 0.75), Example 19-1 ((Br + I) / X = 0.63), Example 20-1 ((Br + I) / X = 0.50), Example 21-1 ((Br + I) / X = 0.38), and Comparative Example 6-1 ((Br + I) / X = 0.25). These are solid electrolytes obtained by heat treatment at a temperature near the crystallization temperature T1°C of the solid electrolyte production material used in each example.

[0182] [Evaluation] (Measurement of Ionic Conductivity) The ionic conductivity (σ) of each solid electrolyte of the Examples and Comparative Examples at 25°C was measured. ２５The AC impedance of each of the samples was measured by the method described above using a Bio-Logic VMP-300. The measurement results are shown in Tables 1 to 3.

[0183]

[0184]

[0185]

[0186] In each of the solid electrolytes of the Examples shown in Tables 1 to 3, even those obtained by heat treatment at 270°C had ionic conductivity (σ ２５ On the other hand, the solid electrolytes of Comparative Examples 1 to 5, which have a molar ratio (Si / (P+Si)) of less than 0.12 shown in Tables 1 and 3, had a σ of the solid electrolytes obtained by heat treatment at 230°C or 270°C. ２５ The σ of the solid electrolyte obtained by heat treatment at a temperature above 230°C was low and the heat resistance was poor. In the solid electrolytes of Comparative Examples 1, 2, 4, and 5, which did not have results of heat treatment at a temperature above 230°C (for example, 270°C), it can be determined that the ionic conductivity is further reduced when the solid electrolyte is heat treated at a temperature above 230°C (for example, 270°C). In addition, the solid electrolyte of Comparative Example 6, which has a molar ratio ((Br+I) / X) of less than 0.30 shown in Table 3, also has a σ of the solid electrolyte obtained by heat treatment at 270°C. ２５ was low and the heat resistance was poor.

[0187] For example, in Example 2, T1 was 208°C, and the ionic conductivity of the solid electrolyte of Example 2-1, which was heat-treated at 210°C near T1°C, was 3.5 mS / cm at 25°C, while the ionic conductivity of the solid electrolyte of Example 2-3, which was heat-treated at 250°C near (T1+40)°C, was 6.4 mS / cm at 25°C. From these results, it can be seen that the ratio (σ Ｔ１＋４０ / σ Ｔ１) is estimated to be about 1.8. On the other hand, for example, in Comparative Example 1, T1 was 187°C, and the ionic conductivity at 25°C of the solid electrolyte of Comparative Example 1-1, which was heat-treated at 190°C near T1°C, was 3.7 mS / cm, and the ionic conductivity at 25°C of the solid electrolyte of Comparative Example 1-3, which was heat-treated at 230°C near (T1+40)°C, was 0.18 mS / cm. From these results, it can be seen that the ratio (σ Ｔ１＋４０ / σ Ｔ１ ) is estimated to be about 0.05. Ｔ１＋４０ / σ Ｔ１ ) is an index of heat resistance, and when Example 2 is compared with Comparative Example 1, it can be said that Example 2 has high heat resistance and Comparative Example 1 has low heat resistance.

[0188] Furthermore, as shown in FIG. 4, in each solid electrolyte obtained by heat treatment near T1 ° C., diffraction peaks appeared in the diffraction angle 2θ range of 20.0 ° ± 0.5 ° and the diffraction angle 2θ range of 29.3 ° ± 0.5 °, confirming the precipitation of HICP. As shown in FIG. 5, in the solid electrolyte of Comparative Example 3-4 obtained by heat treatment at 270 ° C., a diffraction peak appeared in the diffraction angle 2θ range of 17.5 ° ± 0.5 °, suggesting that the HICP underwent a phase transition to LICP or the like. On the other hand, in each solid electrolyte of Examples 2-4, 3-3, and 4-3 obtained by heat treatment at 270 ° C., no diffraction peak appeared in the diffraction angle 2θ range of 17.5 ° ± 0.5 ° or the diffraction peak in this range was low, suggesting that the thermal stability of the HICP was high. As shown in FIG. 6, the crystallinity tended to increase as the molar ratio (Li / (P + Si)) decreased. This high crystallinity is thought to contribute to the improvement of ionic conductivity. In addition, in all of the solid electrolytes of the Examples obtained by heat treatment at around T1°C, diffraction peaks appeared in the range of a diffraction angle 2θ of 20.0°±0.5° and a diffraction angle 2θ of 29.3°±0.5°, but no diffraction peak appeared in the range of a diffraction angle 2θ of 17.5°±0.5°.

[0189] The present invention can be applied to power storage elements used as power sources for electronic devices such as personal computers and communication terminals, automobiles, industrial equipment, and the like.

[0190] REFERENCE SIGNS LIST 1 Energy storage element 2 Positive electrode 3 Negative electrode 4 Separator layer 5 Positive electrode substrate 6 Positive electrode active material layer 7 Negative electrode substrate 8 Negative electrode active material layer 20 Energy storage unit 30 Energy storage device

Claims

Contains lithium, phosphorus, silicon, sulfur and halogen elements, a molar ratio (Si / (P+Si)) of the content of the silicon element to the total content of the phosphorus element and the silicon element is 0.12 or more; the halogen element includes at least one of a bromine element and an iodine element, a molar ratio ((Br+I) / X) of the total content of the bromine element and the iodine element to the content of the halogen element is 0.30 or more; In an X-ray diffraction pattern using CuKα radiation, the crystal has diffraction peaks in the range of a diffraction angle 2θ of 20.0°±0.5° and in the range of a diffraction angle 2θ of 29.3°±0.5°, A solid electrolyte in which, in the X-ray diffraction pattern, there is no diffraction peak within a diffraction angle 2θ range of 17.5°±0.5°, or there is a diffraction peak within a diffraction angle 2θ range of 17.5°±0.5°, and the intensity of the diffraction peak within the diffraction angle 2θ range of 17.5°±0.5° is ⅕ or less of the intensity of the diffraction peak within the diffraction angle 2θ range of 20.0°±0.5°.

2. The solid electrolyte according to claim 1, wherein the molar ratio (Si / (P+Si)) is 0.55 or less.

3. The solid electrolyte according to claim 1, wherein the molar ratio (Si / (P+Si)) is 0.50 or less.

3. The solid electrolyte according to claim 1, wherein a molar ratio (Li / (P+Si)) of the content of the lithium element to the total content of the phosphorus element and the silicon element is 3.10 or more and less than 3.

70. The solid electrolyte according to claim 1, represented by the following formula (1): Li ａ (P) １－ｂ Yes ｂ )S ｃ X ｄ Z ｅ ・・・(1) (In formula (1), X is a halogen element including at least one of bromine and iodine. Z is at least one element other than Li, P, Si, S, and X. a, b, c, d, and e satisfy the following relationships: 3.00≦a≦3.80, 0.12≦b<1.00, 3.00≦c≦4.20, 0.01≦d≦1.00, and 0≦e≦1.00, respectively.) 3. The solid electrolyte according to claim 1, wherein the ionic conductivity at 25°C is 1.0 mS / cm or more.

3. The solid electrolyte according to claim 1, wherein the ionic conductivity at 25°C after heat treatment at 270°C for 2 hours is 1.0 mS / cm or more. 　 Contains lithium, phosphorus, silicon, sulfur and halogen elements, a molar ratio (Si / (P+Si)) of the content of the silicon element to the total content of the phosphorus element and the silicon element is 0.12 or more; the halogen element includes at least one of a bromine element and an iodine element, a molar ratio ((Br+I) / X) of the total content of the bromine element and the iodine element to the content of the halogen element is 0.30 or more; The ionic conductivity σ at 25°C after heat treatment for 2 hours at T1°C, which is the lowest temperature among the one or more crystallization temperatures, is σ Ｔ１ Ionic conductivity σ at 25 ° C. after heat treatment at (T1 + 40) ° C. for 2 hours Ｔ１＋４０ The ratio of (σ Ｔ１＋４０ / σ Ｔ１ ) is 0.7 or more. 　 A method for producing a solid electrolyte, comprising: heat-treating the material for producing a solid electrolyte according to claim 8; The method for producing a solid electrolyte includes a period of time during which the heat treatment is maintained at a temperature equal to or higher than T1°C. 　 The method for producing a solid electrolyte according to claim 9 , wherein the maximum temperature in the heat treatment is 400° C. or less. 　 heat-treating a material for producing a solid electrolyte; The material for producing a solid electrolyte contains lithium, phosphorus, silicon, sulfur, and a halogen element, a molar ratio (Si / (P+Si)) of the content of the silicon element to the total content of the phosphorus element and the silicon element is 0.12 or more; the halogen element includes at least one of a bromine element and an iodine element, a molar ratio ((Br+I) / X) of the total content of the bromine element and the iodine element to the content of the halogen element is 0.30 or more; The method for producing a solid electrolyte, wherein the heat treatment includes a period of time during which the temperature is maintained at 200°C or higher, and the maximum temperature during the heat treatment is 400°C or lower. 　 A solid electrolyte obtained by the method for producing a solid electrolyte according to any one of claims 9 to 11. 　 An electric storage element comprising the solid electrolyte according to claim 1 or 2.

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