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

Abstract

A solid electrolyte according to one aspect of the present invention contains a lithium element, a phosphorus element, a silicon element, a sulfur element, and a halogen element, and has a crystal structure, in which the 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 0.25-0.85 inclusive, the molar ratio (X / (P+Si)) of the content of the halogen element to the total content of the phosphorus element and the silicon element is 0.35 or more, and the halogen element does not contain a chlorine element, or the halogen element contains the chlorine element and the molar ratio (Cl / (P+Si)) of the content of the chlorine element to the total content of the phosphorus element and the silicon element is 0.30 or less.

Description

Solid electrolyte, method for producing solid electrolyte, and energy storage element

[0001] The present invention relates to a solid electrolyte, a method for producing the solid electrolyte, and an electric 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. 2024-073233

[0005] A solid electrolyte used in an energy storage device is desired to have high ionic conductivity. In addition, the solid electrolyte is desired to have high oxidation resistance, particularly when used in a positive electrode.

[0006] An object of the present invention is to provide a solid electrolyte having high ionic conductivity and oxidation resistance, a method for producing such 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, and has a crystalline structure, wherein the molar ratio (Si / (P+Si)) of the content of the silicon to the total content of the phosphorus and the silicon is 0.25 or more and 0.85 or less, the molar ratio (X / (P+Si)) of the content of the halogen to the total content of the phosphorus and the silicon is 0.35 or more, and the halogen does not contain chlorine, or the halogen contains chlorine and the molar ratio (Cl / (P+Si)) of the content of the chlorine to the total content of the phosphorus and the silicon is 0.30 or less.

[0008] A solid electrolyte according to another aspect of the present invention is 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. Z is at least one element other than Li, P, Si, S, and X. a, b, c, d, and e satisfy 3.00≦a≦4.00, 0.25≦b≦0.85, 3.50≦c≦4.50, 0.35≦d≦1.10, and 0≦e≦0.50, respectively. When the molar ratio of the content of chlorine element to the content of X is m, dm satisfies 0≦dm≦0.30.)

[0009] 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 to the total content of the phosphorus and the silicon is 0.25 or more and 0.85 or less, the molar ratio (X / (P+Si)) of the content of the halogen to the total content of the phosphorus and the silicon is 0.35 or more, and the halogen does not contain chlorine, or the halogen contains chlorine and the molar ratio (Cl / (P+Si)) of the content of the chlorine to the total content of the phosphorus and the silicon is 0.30 or less.

[0010] An electric storage device according to another aspect of the present invention contains the solid electrolyte according to the aspect of the present invention.

[0011] According to any one aspect of the present invention, it is possible to provide a solid electrolyte having high ionic conductivity and oxidation resistance, a method for producing such a solid electrolyte, and an energy storage element using such a solid electrolyte.

[0012] 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 view showing an energy storage device including energy storage elements according to a plurality of embodiments of the present invention. Fig. 3 is a first X-ray diffraction diagram for each solid electrolyte of the Examples and Comparative Examples. Fig. 4 is a second X-ray diffraction diagram for each solid electrolyte of the Examples and Comparative Examples. Fig. 5 is a third X-ray diffraction diagram for each solid electrolyte of the Examples and Comparative Examples.

[0013] First, an outline of the solid electrolyte, the method for producing the solid electrolyte, and the energy storage device disclosed in this specification will be described.

[0014] [1] A solid electrolyte according to one aspect of the present invention contains lithium, phosphorus, silicon, sulfur, and a halogen, and has a crystalline structure, wherein the molar ratio (Si / (P+Si)) of the content of the silicon to the total content of the phosphorus and the silicon is 0.25 or more and 0.85 or less, the molar ratio (X / (P+Si)) of the content of the halogen to the total content of the phosphorus and the silicon is 0.35 or more, and the halogen does not contain chlorine, or the halogen contains chlorine and the molar ratio (Cl / (P+Si)) of the content of the chlorine to the total content of the phosphorus and the silicon is 0.30 or less.

[0015] The solid electrolyte described in [1] above has high ionic conductivity and oxidation resistance. While the reason for this is unclear, the following reasons are presumed. It is believed that halogen elements contribute to the formation of a crystalline structure with high ionic conductivity in a solid electrolyte containing lithium, phosphorus, and sulfur. However, according to the inventors' knowledge, among halogen elements, chlorine is an element that is relatively unlikely to contribute to the formation of a crystalline structure with high ionic conductivity in the solid electrolyte. Furthermore, by substituting a portion of the phosphorus element in the solid electrolyte with silicon, oxidation resistance tends to be improved. Furthermore, ionic conductivity can be maintained by suppressing the amount of phosphorus substituted by silicon. For these reasons, it is presumed that the solid electrolyte described in [1] above, which contains a halogen element, moderately substitutes a portion of the phosphorus element with silicon, and has a suppressed chlorine content, has high ionic conductivity and oxidation resistance.

[0016] The quantitative determination of each element contained in the solid electrolyte is carried out by the following method. Sulfur element is quantified by combustion-infrared absorption spectroscopy (CS meter). Lithium element, phosphorus element, silicon element, halogen element, and optional elements (elements other than lithium element, phosphorus element, silicon element, sulfur element, and halogen element) are quantified by inductively coupled plasma atomic emission spectroscopy (ICP-AES). However, among the optional elements, hydrogen element and oxygen element are quantified by inert gas fusion-infrared absorption spectroscopy. Among the optional elements, nitrogen element is quantified by inert gas fusion-thermal conductivity spectroscopy. Among the optional elements, carbon element is quantified by combustion-infrared absorption spectroscopy. Note that, regarding the quantitative determination method for each element, if it is difficult to measure using each of the above-mentioned methods, another method that is thought to produce equivalent measurement results can be used.

[0017] [2] In the solid electrolyte according to [1] above, the halogen element may include at least one of a bromine element and an iodine element.

[0018] The solid electrolyte described in [2] above has higher ionic conductivity and oxidation resistance.

[0019] [3] In the solid electrolyte according to [1] or [2] above, the molar ratio (X / (P+Si)) of the content of the halogen element to the total content of the phosphorus element and the silicon element may be 0.80 or less.

[0020] The solid electrolyte described in [3] above has higher ionic conductivity.

[0021] [4] In the solid electrolyte according to any one of [1] to [3] above, in an X-ray diffraction pattern using CuKα radiation, a diffraction peak A may be present in a range of a diffraction angle 2θ of 20.2°±0.2°, and a diffraction peak B may be present in a range of a diffraction angle 2θ of 29.6°±0.2°.

[0022] In an X-ray diffraction pattern using CuKα radiation, a crystal structure having diffraction peaks in the range of a diffraction angle 2θ of 20.2°±0.2° and in the range of a diffraction angle 2θ of 29.6°±0.2° is a high ion conduction phase (HICP). Therefore, the solid electrolyte described in [4] above has higher ionic conductivity.

[0023] 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 difficult 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. The method for calculating the intensity of each diffraction peak from powder X-ray diffraction measurement data is as follows. Using Rigaku's software PDXL, calculated data is obtained from the X-ray diffraction measurement data by automatic reading, and the diffraction peak intensities are read. In the automatic reading process, smoothing, background processing, background refinement, Kα2 removal, and automatic fitting are performed to obtain calculated data.

[0024] [5] In the solid electrolyte according to any one of [1] to [4] above, in an X-ray diffraction diagram using CuKα radiation, a diffraction peak D is in the range of a diffraction angle 2θ of 27.7°±0.2°, a diffraction peak E is in the range of a diffraction angle 2θ of 28.6°±0.2°, a diffraction peak F is in the range of a diffraction angle 2θ of 29.1°±0.2°, and a diffraction peak G is in the range of a diffraction angle 2θ of 30.1°±0.2°.

[0025] The solid electrolyte described in [5] above has higher oxidation resistance.

[0026] [6] The solid electrolyte according to any one of [1] to [5] above may have an ionic conductivity of 1.0 mS / cm or more at 25°C.

[0027] The solid electrolyte described in [6] above has particularly sufficient ionic conductivity.

[0028] 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 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)

[0029] [7] In the solid electrolyte according to any one of [1] to [6] above, Li may be represented by the following formula (1): ａ (P １－ｂ Si ｂ ) S ｃ X ｄ Z ｅ ... (1) (In formula (1), X is a halogen element. Z is at least one element other than Li, P, Si, S, and X. a, b, c, d, and e satisfy 3.00≦a≦4.00, 0.25≦b≦0.85, 3.50≦c≦4.50, 0.35≦d≦1.10, and 0≦e≦0.50, respectively. When the molar ratio of the content of chlorine element to the content of X is m, dm satisfies 0≦dm≦0.30.)

[0030] The solid electrolyte described in [7] above contains a halogen element and has a portion of the phosphorus element appropriately substituted with silicon element, and therefore has high ionic conductivity and oxidation resistance.

[0031] [8] The solid electrolyte according to any one of [1] to [7] above may be a solid electrolyte for a positive electrode.

[0032] [9] In the solid electrolyte according to any one of [1] to [8] above, in the X-ray diffraction pattern, a diffraction peak C may be present in the range of a diffraction angle 2θ of 33.3°±0.2°.

[0033] The solid electrolyte described in [8] or [9] above is also a suitable embodiment of the present invention.

[0034]

[10] 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, wherein the material for producing a solid electrolyte contains lithium, phosphorus, silicon, sulfur, and a halogen, wherein a molar ratio (Si / (P+Si)) of the content of the silicon to a total content of the phosphorus and the silicon is 0.25 or more and 0.85 or less, a molar ratio (X / (P+Si)) of the content of the halogen to a total content of the phosphorus and the silicon is 0.35 or more, and the halogen does not contain chlorine, or the halogen contains chlorine and a molar ratio (Cl / (P+Si)) of the content of the chlorine to a total content of the phosphorus and the silicon is 0.30 or less.

[0035] According to the method for producing a solid electrolyte described in

[10] above, a solid electrolyte having high ionic conductivity and oxidation resistance can be produced.

[0036]

[11] An electric storage device according to another aspect of the present invention contains the solid electrolyte according to any one of [1] to [9] above.

[0037] The electric storage element according to the above

[11] contains a solid electrolyte having high ionic conductivity and oxidation resistance, and therefore has good charge / discharge performance.

[0038] 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.

[0039] In addition, the lower limit and upper limit of each numerical range described in the embodiments of the present invention can be combined arbitrarily. Unless otherwise specified, the lower limit and upper limit of a numerical range include the lower limit and upper limit. In other words, a lower limit of A means that the range is A or more. Similarly, an upper limit of B means that the range is B or less.

[0040] <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 a substance that exhibits ion conductivity and 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.

[0041] With respect 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 0.25, preferably 0.28, more preferably 0.30, and may be 0.40, 0.50, 0.60, or 0.70. When the molar ratio (Si / (P+Si)) is equal to or greater than the above lower limit, oxidation resistance can be improved. The upper limit of the molar ratio (Si / (P+Si)) is 0.85, preferably 0.82, more preferably 0.80, even more preferably 0.75, even more preferably 0.70, and may be 0.65, 0.60, 0.50, or 0.40. When the molar ratio (Si / (P+Si)) is equal to or less than the above upper limit, the ionic conductivity of the solid electrolyte can be increased.

[0042] The lower limit of the molar ratio (P / (P+Si)) of the content of elemental phosphorus to the total content of elemental phosphorus and elemental silicon is 0.15, preferably 0.18, more preferably 0.20, even more preferably 0.25, still more preferably 0.30, and may be 0.35, 0.40, 0.50, or 0.60. When the molar ratio (P / (P+Si)) is equal to or greater than the above lower limit, the ionic conductivity of the solid electrolyte can be increased. The upper limit of the molar ratio (P / (P+Si)) is 0.75, preferably 0.72, more preferably 0.70, and may be 0.60, 0.50, 0.40, or 0.30. When the molar ratio (P / (P+Si)) is equal to or less than the above upper limit, the oxidation resistance of the solid electrolyte can be increased.

[0043] 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 0.35, preferably 0.40, more preferably 0.45, and even more preferably 0.50. When the molar ratio (X / (P+Si)) is equal to or greater than the above lower limit, the ionic conductivity of the solid electrolyte can be increased. The upper limit of the molar ratio (X / (P+Si)) may be 1.10, 1.00, or 0.90, but is preferably 0.80, more preferably 0.75, even more preferably 0.70, even more preferably 0.60, and may be 0.55 or 0.50. When the molar ratio (X / (P+Si)) is equal to or less than the above upper limit, the ionic conductivity and oxidation resistance of the solid electrolyte can be increased.

[0044] 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 is preferably 3.00, more preferably 3.10, even more preferably 3.20, and even more preferably 3.30, 3.35, 3.40, 3.45, or 3.50. When the molar ratio (Li / (P+Si)) is not less than the above lower limit, the ionic conductivity and oxidation resistance of the solid electrolyte can be further increased. The upper limit of the molar ratio (Li / (P+Si)) is preferably 4.00, more preferably 3.90, even more preferably 3.80, and even more preferably 3.70, 3.65, 3.60, 3.55, or 3.50. When the molar ratio (Li / (P+Si)) is not more than the above upper limit, the ionic conductivity and oxidation resistance of the solid electrolyte can be further increased.

[0045] The lower limit of the molar ratio (S / (P+Si)) of the content of elemental sulfur to the total content of elemental phosphorus and elemental silicon is preferably 3.50, more preferably 3.60, and may be 3.65, 3.70, 3.75, or 3.85. The upper limit of the molar ratio (S / (P+Si)) is preferably 4.50, more preferably 4.40, even more preferably 4.30, and even more preferably 4.20, 4.10, 4.00, 3.95, or 3.90. When the molar ratio (S / (P+Si)) is within the above range, the ionic conductivity and oxidation resistance of the solid electrolyte can be further improved.

[0046] The halogen element contained in the solid electrolyte preferably includes at least one of bromine and iodine, and more preferably includes both bromine and iodine. The solid electrolyte can further improve its ionic conductivity and oxidation resistance by including these halogen elements. The solid electrolyte may also include halogen elements other than bromine and iodine (e.g., fluorine, chlorine). The solid electrolyte may also be substantially free of halogen elements other than bromine and iodine (e.g., fluorine, chlorine).

[0047] The upper limit of the molar ratio (Cl / (P+Si)) of the content of elemental chlorine to the total content of elemental phosphorus and elemental silicon is 0.30, preferably less than 0.30, more preferably 0.20, even more preferably 0.10, and even more preferably 0.05. The molar ratio (Cl / (P+Si)) may be 0.00. That is, in the solid electrolyte, the halogen elements do not contain elemental chlorine, or the halogen elements contain elemental chlorine and the molar ratio (Cl / (P+Si)) is 0.30 or less. By having the molar ratio (Cl / (P+Si)) within the above range, it is possible to improve the ionic conductivity and oxidation resistance of the solid electrolyte.

[0048] The upper limit of the molar ratio (Cl / X) of the chlorine element content to the halogen element content is preferably 0.60, more preferably less than 0.60, even more preferably 0.50 or less, and even more preferably 0.40, 0.30, 0.20, or 0.10. The molar ratio (Cl / X) may be 0.00. That is, it is preferable that the halogen element in the solid electrolyte does not contain chlorine element, or that the halogen element contains chlorine element and the molar ratio (Cl / X) is 0.60 or less. By having the molar ratio (Cl / X) within the above range, it is possible to further improve the ionic conductivity and oxidation resistance of the solid electrolyte.

[0049] The lower limit of the molar ratio (Br / (P+Si)) of the content of elemental bromine to the total content of elemental phosphorus and elemental silicon is preferably 0.20, more preferably 0.25, still more preferably 0.28, and may be 0.30. The upper limit of the molar ratio (Br / (P+Si)) is preferably 0.60, more preferably 0.50, and may be 0.45 or 0.40. When the molar ratio (Br / (P+Si)) is within the above range, the ionic conductivity of the solid electrolyte can be further increased, for example.

[0050] The lower limit of the molar ratio (Br / X) of the content of bromine element to the content of halogen element is preferably 0.30, more preferably 0.40, and may be 0.50 or 0.60. The upper limit of the molar ratio (Br / X) is preferably 0.90, more preferably 0.80, and may be 0.75 or 0.70. When the molar ratio (Br / X) is within the above range, the ionic conductivity of the solid electrolyte can be further increased.

[0051] The lower limit of the molar ratio (I / (P+Si)) of the content of elemental iodine to the total content of elemental phosphorus and elemental silicon is preferably 0.10, more preferably 0.15, still more preferably 0.18, and may be 0.20. The upper limit of the molar ratio (I / (P+Si)) is preferably 0.50, more preferably 0.40, and may be 0.35 or 0.30. When the molar ratio (I / (P+Si)) is within the above range, the ionic conductivity of the solid electrolyte can be further increased, for example.

[0052] 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 may be 0.30 or 0.40. The upper limit of the molar ratio (I / X) is preferably 0.70, more preferably 0.60, and may be 0.55 or 0.50. When the molar ratio (I / X) is within the above range, the ionic conductivity of the solid electrolyte can be further increased.

[0053] The lower limit of the molar ratio ((Br + I) / (P + Si)) of the total content of bromine and iodine elements to the total content of phosphorus and silicon elements is preferably 0.35, more preferably 0.40, even more preferably 0.45, and even more preferably 0.50. When the molar ratio ((Br + I) / (P + Si)) is equal to or greater than the above lower limit, the ionic conductivity of the solid electrolyte can be further increased. The upper limit of the molar ratio ((Br + I) / (P + Si)) is 0.80, preferably 0.75, more preferably 0.70, even more preferably 0.60, and may be 0.55 or 0.50. When the molar ratio ((Br + I) / (P + Si)) is equal to or less than the above upper limit, the ionic conductivity and oxidation resistance of the solid electrolyte can be further increased.

[0054] The lower limit of the molar ratio ((Br + I) / X) of the total content of bromine element and iodine element in the content of halogen element is preferably 0.35, more preferably 0.40, even more preferably 0.60, even more preferably 0.80, and may be 0.90 or 0.95. When the molar ratio ((Br + I) / X) is equal to or greater than the above lower limit, the ionic conductivity and oxidation resistance of the solid electrolyte can be further improved. The upper limit of the molar ratio ((Br + I) / X) is preferably 1.00, and may be 0.95 or 0.90.

[0055] The solid electrolyte may be substantially free of halogen elements (X') other than bromine and iodine. The upper limit of the molar ratio (X' / X) of the content of the other halogen elements (X') relative to the content of the halogen element (X) is preferably 0.15, more preferably 0.10, even more preferably 0.05, and even more preferably 0.01. The molar ratio (X' / X) may be 0. The upper limit of the molar ratio (X' / (P+Si)) of the content of the other halogen elements relative to the total content of phosphorus and silicon is preferably 0.20, more preferably 0.15, and even more preferably 0.10, 0.05, or 0.01. The molar ratio (X' / (P+Si)) may be 0.

[0056] 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 0.15, more preferably 0.10, further preferably 0.05, and even more preferably 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 is preferably 0.20, more preferably 0.15, and further preferably 0.10, 0.05, or 0.01. The molar ratio (F / (P+Si)) may be 0.

[0057] 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 0.50, more preferably 0.30, and even more preferably 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 the ionic conductivity and oxidation resistance of the solid electrolyte. 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.

[0058] 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 0.50, or may be 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.

[0059] 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 0.50, or may be 0.40, 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.

[0060] 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. Z is at least one element other than Li, P, Si, S, and X. a, b, c, d, and e satisfy 3.00≦a≦4.00, 0.25≦b≦0.85, 3.50≦c≦4.50, 0.35≦d≦1.10, and 0≦e≦0.50, respectively. When the molar ratio of the content of chlorine element to the content of X is m, dm satisfies 0≦dm≦0.30. Note that dm is the product of d and m.)

[0061] When the solid electrolyte has a composition represented by the above formula (1), it can further improve ionic conductivity and oxidation resistance. 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 relative 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 molar ratio (Si / (P+Si)) described above, the preferred range of c is the same as the preferred range of the molar ratio (S / (P+Si)) described above, the preferred range of d is the same as the preferred range of the molar ratio (X / (P+Si)) described above, the preferred range of e is the same as the preferred range of the molar ratio (Z / (P+Si)) described above, and the preferred range of dm is the same as the preferred range of the molar ratio (Cl / (P+Si)) described above. The preferred ranges of other contents in the solid electrolyte represented by the above formula (1), such as the content of chlorine element in the content of halogen elements, are the same as the preferred ranges described above.

[0062] (Crystalline Structure) The solid electrolyte according to one embodiment of the present invention has a crystalline structure. Here, "having a crystalline structure" means that in an X-ray diffraction measurement, a peak derived from the crystalline structure of the solid electrolyte is observed in the X-ray diffraction pattern. The solid electrolyte may contain an amorphous portion. A solid electrolyte having a crystalline structure can be obtained, for example, by crystallizing an amorphous solid electrolyte by heat treatment or the like.

[0063] In an X-ray diffraction diagram using CuKα radiation, the solid electrolyte preferably has a diffraction peak A in the diffraction angle 2θ range of 20.2°±0.2° and a diffraction peak B in the diffraction angle 2θ range of 29.6°±0.2°. In this case, since the solid electrolyte has a HICP crystal structure, the ionic conductivity is higher. In the X-ray diffraction diagram, of all diffraction peaks present in the diffraction angle 2θ range of 10.0° to 40.0°, diffraction peak B in the diffraction angle 2θ range of 29.6°±0.2° may be the diffraction peak with the highest peak intensity. In the X-ray diffraction diagram, of all diffraction peaks present in the diffraction angle 2θ range of 10.0° to 40.0°, diffraction peak A in the diffraction angle 2θ range of 20.2°±0.2° may be the diffraction peak with the second highest peak intensity.

[0064] The solid electrolyte may partially have a crystal structure other than HICP. Other crystal structures include LGPS type, argyrodite type, Li ７ P ３ S １１ , Thio-LISICON, etc. The solid electrolyte may have an amorphous portion.

[0065] In the X-ray diffraction diagram, the solid electrolyte preferably has a diffraction peak C in the range of a diffraction angle 2θ of 33.3°±0.2°. In this case, the solid electrolyte has higher ionic conductivity.

[0066] In the X-ray diffraction diagram, the solid electrolyte preferably has a diffraction peak D at a diffraction angle 2θ of 27.7°±0.2°, a diffraction peak E at a diffraction angle 2θ of 28.6°±0.2°, a diffraction peak F at a diffraction angle 2θ of 29.1°±0.2°, and a diffraction peak G at a diffraction angle 2θ of 30.1°±0.2°. In this case, the solid electrolyte has higher ionic conductivity.

[0067] (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 1.5 mS / cm, even more preferably 2.0 mS / cm, and even more preferably 3.0 mS / cm, 4.0 mS / cm, 4.5 mS / cm, or 5.0 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, and may be, for example, 20 mS / cm, 10 mS / cm, 8.0 mS / cm, 6.0 mS / cm, or 5.0 mS / cm.

[0068] 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. Because the solid electrolyte has high ionic conductivity and oxidation resistance, it can be particularly suitably used in a positive electrode.

[0069] <Method for Producing Solid Electrolyte> A method for producing a solid electrolyte according to one embodiment of the present invention includes heat treating a material for producing a solid electrolyte. The material for producing a solid electrolyte used in this method contains lithium, phosphorus, silicon, sulfur, and a halogen, wherein the molar ratio of the silicon content to the total content of the phosphorus and the silicon (Si / (P+Si)) is 0.25 to 0.85, the molar ratio of the halogen content to the total content of the phosphorus and the silicon (X / (P+Si)) is 0.35 or more, and the halogen does not contain chlorine, or the halogen contains chlorine and the molar ratio of the chlorine content to the total content of the phosphorus and the silicon (Cl / (P+Si)) is 0.30 or less.

[0070] The specific and preferred elemental compositions of the material for producing a solid electrolyte are the same as the specific and preferred elemental compositions of the solid electrolyte according to one embodiment of the present invention described above.

[0071] 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.

[0072] Examples of compounds containing lithium include Li ２ S., Li. ２ O, Li ３ N., Li. ２ CO ３ , metallic lithium, LiCl, LiBr, LiI, etc. Among these, Li ２ S, LiCl, LiBr and LiI are preferred. The lithium element-containing compounds may be used alone or in combination of two or more.

[0073] 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.

[0074] Examples of compounds containing silicon include SiS, SiS ２ , SiO ２ Among these, SiS ２ The silicon-containing compound is preferably a silicon sulfide. The silicon-containing compound may be used alone or in combination of two or more.

[0075] 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.

[0076] Examples of compounds containing halogen elements include lithium halides and simple halogens, such as LiCl, LiI, LiBr, and Cl. ２ , I ２ ,Br ２ Among these, LiI and LiBr are preferred. Two or more halogen-containing compounds can be used in combination.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] In this production method, a solid electrolyte at least partly having a HICP crystal structure 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.

[0082] In a method for producing a solid electrolyte according to one embodiment of the present invention, the heat treatment involves raising the temperature to a maximum heat treatment temperature set within a specific temperature range and maintaining the temperature. In this production method, the heat treatment is performed on a material for producing a solid electrolyte by raising the temperature to a maximum heat treatment temperature set within a specific temperature range and maintaining the temperature. This results in a solid electrolyte having high ionic conductivity, at least a portion of which has precipitated the HICP crystal structure. The lower limit of the maximum heat treatment temperature during the heat treatment is preferably 180°C, and may be 200°C, 220°C, 240°C, 260°C, 280°C, or 300°C. The upper limit of the maximum heat treatment temperature during the heat treatment is preferably 390°C, more preferably 370°C, or may be 350°C, 330°C, or 320°C. By setting the maximum heat treatment temperature within the above range, a crystalline phase exhibiting high ionic conductivity can be precipitated as the main phase. The time for maintaining the maximum heat treatment temperature is preferably 1 hour to 24 hours, and more preferably 2 hours to 12 hours. The upper limit of the time for which the temperature is maintained at the maximum heat treatment temperature may be 10 hours or 5 hours.

[0083] The solid electrolyte obtained by the above-described method for producing a solid electrolyte may also be one embodiment of the present invention.

[0084] <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 may be an all-solid-state electric storage element or an all-solid-state battery.

[0085] 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 .

[0086] The energy storage device 1 contains a solid electrolyte according to one 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 one 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 device 1 contains a solid electrolyte having high ionic conductivity and oxidation resistance, and therefore has good charge / discharge performance. The energy storage device 1 preferably contains a solid electrolyte according to one embodiment of the present invention in the positive electrode 2, more specifically, in the positive electrode active material layer 6. Because the solid electrolyte according to one embodiment of the present invention has high ionic conductivity and oxidation resistance, when used in the positive electrode, the energy storage device 1 can exhibit particularly good charge / discharge performance.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] Examples of sulfide solid electrolytes other than the solid electrolyte according to one embodiment of the present invention include Li ２ S-P ２ S５ 、 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 (However, m, n are positive numbers, and Z is any one of Ge, Zn, Ga.), Li ２ S - GeS ２ 、 Li ２ S - SiS ２ - Li ３ PO 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 In addition, the symbol "-" in the above-mentioned options means that the sulfide solid electrolyte is prepared from a plurality of raw material compositions. For example, the above-mentioned "Li ２ S-P ２ S ５ " is the raw material composition Li ２ S and P ２ S ５ The sulfide solid electrolyte is prepared from

[0091] 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.

[0092] 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.

[0093] (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.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] α-NaFeO ２ As the lithium transition metal composite oxide having a crystalline structure, Li １＋α Ma １－α O２ (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.

[0104] 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.

[0105] 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).

[0106] Examples of the chalcogen compound include titanium disulfide, molybdenum disulfide, and molybdenum dioxide.

[0107] 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.

[0108] 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.

[0109] 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 positive electrode active material is easily manufactured or handled. 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.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] 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 －２ Conductive 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 of these materials. For example, a composite of carbon black and CNT may be used.

[0115] 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.

[0116] Examples of the binder include a water-based binder and an organic solvent-based binder.

[0117] 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.

[0118] 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.

[0119] 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.

[0120] 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.

[0121] 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.

[0122] 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.

[0123] 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.

[0124] 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.

[0125] (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.

[0126] 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.

[0127] 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.

[0128] 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.

[0129] 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.

[0130] 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.

[0131] 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 solid electrolyte may be selected from the materials exemplified above. The optional components such as a conductive agent, a binder, a thickener, and a 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-described 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.

[0132] 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.

[0133] "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.

[0134] "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.

[0135] 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.

[0136] 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.

[0137] 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.

[0138] 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.

[0139] 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.

[0140] 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.

[0141] 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.

[0142] 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.

[0143] 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.

[0144] 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.

[0145] 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 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 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 contained 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 contained impurities in the negative electrode active material layer may be 10% by mass, 5%, 2%, 1%, 0.1%, or 0.01% by mass.

[0146] 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 More than 50mg / cm 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.

[0147] (Isolation Layer) The isolation layer usually contains a solid electrolyte. The solid electrolyte contained in the isolation layer may be the solid electrolyte according to one embodiment of the present invention, or may be a solid electrolyte other than the solid electrolyte according to one embodiment of the present invention. However, it is preferable to use the solid electrolyte according to one embodiment of the present invention. The other solid electrolyte may be selected from the materials exemplified above. 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.

[0148] 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.

[0149] The isolation layer may contain an additive (e.g., Li ３ P.O. ４ The 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.

[0150] 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.

[0151] (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.

[0152] 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.

[0153] (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.

[0154] 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.

[0155] 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.

[0156] 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.

[0157] <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.

[0158] 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.

[0159] 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.

[0160] 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.

[0161] 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.

[0162] 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.

[0163] 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.

[0164] <Other Embodiments> The solid electrolyte, the method for manufacturing the solid electrolyte, and the energy storage element 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.

[0165] 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.

[0166] 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.

[0167] 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.

[0168] [Example 1] 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 out as raw material compounds in a molar ratio of 56.60:13.21:11.32:11.32:7.55, 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. The material for producing the solid electrolyte was heat-treated by heating it to a maximum heat treatment temperature HT set at 310° C. and maintaining it for 2 hours, thereby obtaining the solid electrolyte of Example 1.

[0169] [Examples 2 to 4, Comparative Examples 1 to 6] The amounts (molar ratios) of the raw material compounds used were adjusted to give the composition ratios of the solid electrolytes shown in Table 1. The maximum heat treatment temperature HT was also set to be as shown in Table 1. Except for these points, the solid electrolytes of Examples 2 to 4 and Comparative Examples 1 to 6 were obtained in the same manner as in Example 1.

[0170] [Example 5, Comparative Example 7] The solid electrolytes of Example 5 and Comparative Example 7 were obtained in the same manner as in Example 1, except that LiCl (99.999%, manufactured by Aldrich) was added as a raw material compound and the amounts (molar ratios) of the raw material compounds used were adjusted to give the composition ratios of the solid electrolytes shown in Table 2.

[0171] [Examples 6 to 8] The solid electrolytes of Examples 6 to 8 were obtained in the same manner as in Example 1, except that the amounts (molar ratios) of the raw material compounds used were adjusted to give the composition ratios of the solid electrolytes shown in Table 3.

[0172] 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 chlorine content to the total content of phosphorus and silicon (Cl / (P+Si)), the molar ratio of the halogen element to the total content of phosphorus and silicon (X / (P+Si)), the molar ratio of phosphorus to the total content of phosphorus and silicon (P / (P+Si)), and the molar ratio of silicon to the total content of phosphorus and silicon (Si / (P+Si)). It is to be noted that each solid electrolyte in the examples and comparative examples is considered to contain substantially no elements other than lithium, sulfur, bromine, iodine, chlorine, phosphorus, and silicon.

[0173] The inventors used a material for producing a solid electrolyte containing lithium, sulfur, bromine, iodine, chlorine, phosphorus, and silicon to produce a solid electrolyte having an elemental composition different from that of the above-mentioned Examples and Comparative Examples, and quantified the content of each constituent element in this solid electrolyte by the above-mentioned method. The content ratio of each constituent element in this solid electrolyte was generally consistent with the content ratio of each constituent element in the material for producing a solid electrolyte, i.e., the content ratio of each constituent element in the material used.

[0174] (X-ray Diffraction Measurement) Powder X-ray diffraction measurement was performed for each solid electrolyte of the Examples and Comparative Examples using the method described above to obtain X-ray diffraction patterns. FIG. 3 shows X-ray diffraction patterns for each solid electrolyte of Examples 1 to 4 and Comparative Examples 4 and 5. FIG. 4 shows X-ray diffraction patterns for each solid electrolyte of Examples 1 and 5 and Comparative Example 7. FIG. 5 shows X-ray diffraction patterns for each solid electrolyte of Examples 1, 6 to 8. Note that the dotted lines in each X-ray diffraction pattern indicate the positions of peaks related to preferred embodiments of the present invention.

[0175] 3, in each of the solid electrolytes of Examples 1 to 3, a diffraction peak A was observed in the diffraction angle 2θ range of 20.2° ± 0.2°, and a diffraction peak B was observed in the diffraction angle 2θ range of 29.6° ± 0.2°, confirming that the solid electrolytes had a HICP crystalline structure. Furthermore, in each of the solid electrolytes of Examples 1 to 3, a diffraction peak C was observed in the diffraction angle 2θ range of 33.3° ± 0.2°. Furthermore, in each of the solid electrolytes of Examples 3 and 4, a diffraction peak D was observed in the diffraction angle 2θ range of 27.7° ± 0.2°, a diffraction peak E was observed in the diffraction angle 2θ range of 28.6° ± 0.2°, a diffraction peak F was observed in the diffraction angle 2θ range of 29.1° ± 0.2°, and a diffraction peak G was observed in the diffraction angle 2θ range of 30.1° ± 0.2°.

[0176] 4, it was confirmed that each of the solid electrolytes of Example 5 and Comparative Example 7 had a diffraction peak A in the diffraction angle 2θ range of 20.2°±0.2° and a diffraction peak B in the diffraction angle 2θ range of 29.6°±0.2°, and thus had a HICP crystal structure. Furthermore, each of the solid electrolytes of Example 5 and Comparative Example 7 had a diffraction peak C in the diffraction angle 2θ range of 33.3°±0.2°.

[0177] 5, each of the solid electrolytes of Examples 6 to 8 had a diffraction peak A in the diffraction angle 2θ range of 20.2°±0.2° and a diffraction peak B in the diffraction angle 2θ range of 29.6°±0.2°, confirming that they had a HICP crystalline structure. Furthermore, each of the solid electrolytes of Examples 6 to 8 had a diffraction peak C in the diffraction angle 2θ range of 33.3°±0.2°.

[0178] [Evaluation] [Ionic Conductivity Measurement] The ionic conductivity (σ) of each solid electrolyte of the Examples and Comparative Examples at 25°C was measured. ２５ The AC impedance of each of the samples was measured by the method described above using a VMP-300 manufactured by Bio-Logic. The measurement results are shown in Tables 1, 2 and 3.

[0179] [Evaluation of Oxidation Resistance] The following measurement cells were prepared using each solid electrolyte of the Examples and Comparative Examples, and square wave voltammetry (SWV) measurements were performed. ＭＡＸ The oxidation resistance was evaluated based on the above. In an argon atmosphere with a dew point of -50°C or less, 80 mg of sample powder (solid electrolyte to be measured) was placed in a powder molding machine with an inner diameter of 10 mm, and then uniaxially pressed at 50 MPa or less using a hydraulic press. After releasing the pressure, graphite powder was placed on the upper surface of the sample, and then uniaxially pressed at 360 MPa or less using a hydraulic press for 5 minutes. Next, a metal foil consisting of a metal indium foil and a metal lithium foil bonded to it was placed on the lower surface of the sample, and then uniaxially pressed at 50 MPa or less to obtain a pellet-type measurement cell. This measurement cell was compressed in the stacking direction with a compression jig at a torque of 50 cNm, and SWV measurement was performed under the following measurement conditions. (SWV measurement conditions) Voltage amplitude: 20 mV Relaxation time: 50 ms Step voltage: 1 mV Voltage range: OCV to 4.5 V Measurement temperature: 50°C Measured peak current I ＭＡＸ are shown in Tables 1, 2 and 3. Peak current I ＭＡＸ When the value is small, it is judged that the oxidation resistance is excellent.

[0180]

[0181]

[0182]

[0183] As shown in Table 1, in Comparative Examples 1 to 3 and 6 in which the molar ratio (Si / P+Si) was less than 0.25, the peak current I ＭＡＸ In Comparative Examples 4 and 5, in which the molar ratio (Si / P+Si) was greater than 7.0 and the molar ratio (Si / P+Si) was greater than 0.85, the ionic conductivity σ ２５ In contrast, in Examples 1 to 4 in which the molar ratio (Si / P+Si) was 0.25 or more and 0.85 or less, the molar ratio (X / P+Si) was 0.35 or more, and the molar ratio (Cl / P+Si) was 0.30 or less, the peak current I ＭＡＸ is small and ionic conductivity σ ２５ was as high as 1.0 mS / cm or more.

[0184] As shown in Table 2, when Examples 1 and 5 and Comparative Example 7 were compared in which the molar ratio (Si / P+Si) and the molar ratio (X / P+Si) were the same and the molar ratio (Cl / P+Si) was changed, in Comparative Example 7 in which the molar ratio (Cl / P+Si) exceeded 0.30, the ionic conductivity σ ２５ decreases, and the peak current I ＭＡＸ There was a tendency for this to increase.

[0185] As shown in Table 3, Examples 6 to 8, in which the molar ratio (Si / P+Si) was 0.25 or more and 0.85 or less, the molar ratio (X / P+Si) was 0.35 or more, and the molar ratio (Cl / P+Si) was 0.30 or less, had a peak current I ＭＡＸ is small and ionic conductivity σ ２５ Furthermore, when Examples 1, 6 to 4 are compared, when the molar ratio (X / P+Si) exceeds 0.70, the ionic conductivity σ ２５ decreases, and the peak current I ＭＡＸ There was a tendency for this to increase.

[0186] 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.

[0187] 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

1. A solid electrolyte containing lithium, phosphorus, silicon, sulfur and a halogen, having a crystalline structure, 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 0.25 or more and 0.85 or less, the molar ratio (X / (P+Si)) of the content of the halogen element to the total content of the phosphorus and the silicon element is 0.35 or more, and wherein the halogen element does not contain chlorine, or the halogen element contains chlorine and the molar ratio (Cl / (P+Si)) of the content of the chlorine element to the total content of the phosphorus and the silicon element is 0.30 or less.

2. The solid electrolyte according to claim 1, wherein the halogen element includes at least one of bromine and iodine.

3. A solid electrolyte according to claim 1 or 2, wherein the molar ratio (X / (P+Si)) of the content of said halogen element to the total content of said phosphorus element and said silicon element is 0.80 or less.

4. A solid electrolyte according to claim 1 or 2, which has, in an X-ray diffraction pattern using CuKα radiation, a diffraction peak A in the range of a diffraction angle 2θ of 20.2°±0.2° and a diffraction peak B in the range of a diffraction angle 2θ of 29.6°±0.2°.

5. A solid electrolyte according to claim 1 or 2, which has, in an X-ray diffraction pattern using CuKα rays, a diffraction peak D at a diffraction angle 2θ in the range of 27.7°±0.2°, a diffraction peak E at a diffraction angle 2θ in the range of 28.6°±0.2°, a diffraction peak F at a diffraction angle 2θ in the range of 29.1°±0.2°, and a diffraction peak G at a diffraction angle 2θ in the range of 30.1°±0.2°.

6. The solid electrolyte according to claim 1 or 2, having an ionic conductivity of 1.0 mS / cm or more at 25°C.

7. The solid electrolyte according to claim 1 or 2, which is 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. Z is at least one element other than Li, P, Si, S, and X. a, b, c, d, and e satisfy 3.00≦a≦4.00, 0.25≦b≦0.85, 3.50≦c≦4.50, 0.35≦d≦1.10, and 0≦e≦0.50, respectively. When the molar ratio of the content of chlorine element to the content of X is m, dm satisfies 0≦dm≦0.30.) 8. A method for producing a solid electrolyte, comprising heat treating a material for producing a solid electrolyte, wherein the material for producing a solid electrolyte contains lithium, phosphorus, silicon, sulfur, and a halogen, the 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 0.25 or more and 0.85 or less, the molar ratio (X / (P+Si)) of the content of the halogen element to the total content of the phosphorus element and the silicon element is 0.35 or more, and the halogen element does not contain chlorine, or the halogen element contains chlorine and the molar ratio (Cl / (P+Si)) of the content of the chlorine element to the total content of the phosphorus element and the silicon element is 0.30 or less.

9. An electric storage element containing the solid electrolyte according to claim 1 or 2.

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