Solid electrolyte, solid electrolyte production method, and power storage element

Abstract

A solid electrolyte according to one aspect of the present invention comprises elemental lithium, elemental phosphorus, elemental silicon, elemental sulfur, and a halogen element, wherein the halogen element includes at least one of elemental bromine and elemental iodine, and expression (1), expression (2A), and expression (3) are satisfied. In expression (1), expression (2A), and expression (3), P, Si, S, and X are the mole-based content of the elemental phosphorus, the elemental silicon, the elemental sulfur, and the halogen element, respectively, in the solid electrolyte.　Expression (1): 0.25≤Si / (P+Si)≤0.45 Expression (2A): 3.75≤S / (P+Si)≤4.03 Expression (3): 0.40≤X / (P+Si)

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 element.

[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 Documents 1 and 2 describe sulfide solid electrolytes that contain lithium, phosphorus, and sulfur elements and have a predetermined crystal structure.

[0004] JP 2005-228570 A International Publication No. 2019 / 239949

[0005] The development of new solid electrolytes with high ionic conductivity is desired for use in energy storage devices. Conventional sulfide solid electrolytes have the problem of generating hydrogen sulfide when they come into contact with water.

[0006] An object of the present invention is to provide a solid electrolyte having high ionic conductivity and suppressed generation of hydrogen sulfide, 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 embodiment of the present invention contains lithium, phosphorus, silicon, sulfur, and a halogen element, the halogen element including at least one of bromine and iodine, and satisfies the following formulas (1), (2A), and (3): 0.25≦Si / (P+Si)≦0.45 (1) 3.75≦S / (P+Si)≦4.03 (2A) 0.40≦X / (P+Si) (3) (In formulas (1), (2A), and (3), P, Si, S, and X represent the molar contents of phosphorus, silicon, sulfur, and halogen elements in the solid electrolyte, respectively.)

[0008] A solid electrolyte according to another aspect of the present invention contains lithium, phosphorus, silicon, sulfur, and a halogen element, the halogen element including at least one of bromine and iodine, and satisfies the following formulas (1), (2B), and (3): 0.25≦Si / (P+Si)≦0.45 (1) 0.86≦(Li−X) / (3P+4Si)≦1.02 (2B) 0.40≦X / (P+Si) (3) (In formulas (1), (2B), and (3), Li, P, Si, and X represent the molar contents of lithium, phosphorus, silicon, and the halogen element in the solid electrolyte, respectively.)

[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 a solid electrolyte containing lithium, phosphorus, silicon, sulfur, and a halogen element, the halogen element including at least one of bromine and iodine, and the elemental composition of the material for producing a solid electrolyte satisfies the following formulas (1), (2A), and (3): 0.25≦Si / (P+Si)≦0.45 (1) 3.75≦S / (P+Si)≦4.03 (2A) 0.40≦X / (P+Si) (3) (In formulas (1), (2A), and (3), P, Si, S, and X represent the molar contents of phosphorus, silicon, sulfur, and the halogen element in the material for producing a solid electrolyte, respectively.)

[0010] A method for producing a solid electrolyte according to another aspect of the present invention includes heat treating a material for producing a solid electrolyte, the material for producing a solid electrolyte containing lithium, phosphorus, silicon, sulfur, and a halogen element, the halogen element including at least one of bromine and iodine, and the elemental composition of the material for producing a solid electrolyte satisfies the following formulas (1), (2B), and (3): 0.25≦Si / (P+Si)≦0.45 (1) 0.86≦(Li−X) / (3P+4Si)≦1.02 (2B) 0.40≦X / (P+Si) (3) (In formulas (1), (2B), and (3), Li, P, Si, and X represent the molar contents of lithium, phosphorus, silicon, and the halogen element in the material for producing a solid electrolyte, respectively.)

[0011] An electric storage device according to another aspect of the present invention contains the solid electrolyte according to the aspect of the present invention.

[0012] According to any one aspect of the present invention, it is possible to provide a solid electrolyte having high ionic conductivity and suppressed generation of hydrogen sulfide, a method for producing such a solid electrolyte, and an energy storage element using such a solid electrolyte.

[0013] FIG. 1 is a schematic cross-sectional view showing an all-solid-state battery that is one embodiment of the energy storage element of the present invention. FIG. 2 is a schematic diagram showing an energy storage device including energy storage elements according to several embodiments of the present invention. FIG. 3 is an X-ray diffraction diagram of each solid electrolyte of Examples 1 and 3 and Comparative Example 4. FIG. 4 is an X-ray diffraction diagram of each solid electrolyte of Examples 2, 4, and 5. FIG. 5 is a scatter diagram plotting the amount of hydrogen sulfide generated (ppm) for each solid electrolyte of Examples 1 to 5 and Comparative Examples 2 to 5, with the horizontal axis representing Si / (P+Si) and the vertical axis representing S / (P+Si). FIG. 6 is a scatter diagram plotting the amount of hydrogen sulfide generated (ppm) for each solid electrolyte of Examples 1 to 5 and Comparative Examples 2 to 5, with the horizontal axis representing Si / (P+Si) and the vertical axis representing (Li-X) / (3P+4Si).

[0014] 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.

[0015] [1] A solid electrolyte according to one embodiment of the present invention contains lithium, phosphorus, silicon, sulfur, and a halogen element, the halogen element including at least one of bromine and iodine, and satisfies the following formulas (1), (2A), and (3): 0.25≦Si / (P+Si)≦0.45 (1) 3.75≦S / (P+Si)≦4.03 (2A) 0.40≦X / (P+Si) (3) (In formulas (1), (2A), and (3), P, Si, S, and X represent the molar contents of phosphorus, silicon, sulfur, and halogen elements in the solid electrolyte, respectively.)

[0016] The solid electrolyte described in [1] above has high ionic conductivity and suppresses the generation of hydrogen sulfide. While the reason for this is unclear, the following reason is presumed. In the solid electrolyte described in [1] above, by satisfying the above formula (1), the amount of pentavalent phosphorus replaced with tetravalent silicon is appropriate. Regarding formula (2A), the molar ratio of the sulfur content to the total content of phosphorus and silicon in the solid electrolyte indicates the degree of ortho-composition. In other words, when the value of S / (P+M) in formula (2A) is sufficiently close to 4.00, this means that the solid electrolyte has a favorable composition close to an ortho-composition. It is presumed that the solid electrolyte described in [1] above satisfies formula (1) and formula (2A), thereby having high ionic conductivity and suppressing the generation of hydrogen sulfide. In addition, it is presumed that the solid electrolyte described in [1] above contains a sufficient amount of halogen elements by satisfying formula (3), thereby increasing ionic conductivity.

[0017] The quantitative determination of each element contained in the solid electrolyte is carried out by the following method. Lithium, phosphorus, silicon, sulfur, halogens, and other elements (elements other than lithium, phosphorus, silicon, sulfur, and halogens) are quantified by inductively coupled plasma atomic emission spectrometry (ICP-AES). However, among the other elements, hydrogen and oxygen are quantified by inert gas fusion-infrared absorption spectrometry. Among the other elements, nitrogen is quantified by inert gas fusion-thermal conductivity spectrometry. Among the other elements, carbon is quantified by combustion-infrared absorption spectrometry. Note that, when it is difficult to measure each element using the above-mentioned methods, other methods that are thought to produce equivalent measurement results can be used.

[0018] [2] A solid electrolyte according to one embodiment of the present invention contains lithium, phosphorus, silicon, sulfur, and a halogen element, the halogen element including at least one of bromine and iodine, and satisfies the following formulas (1), (2B), and (3): 0.25≦Si / (P+Si)≦0.45 (1) 0.86≦(Li−X) / (3P+4Si)≦1.02 (2B) 0.40≦X / (P+Si) (3) (In formulas (1), (2B), and (3), Li, P, Si, and X represent the molar contents of lithium, phosphorus, silicon, and the halogen element in the solid electrolyte, respectively.)

[0019] The solid electrolyte described in [2] above has high ionic conductivity and suppresses the generation of hydrogen sulfide. While the reason for this is unclear, the following reason is presumed. The solid electrolyte described in [2] above, like the solid electrolyte described in [1] above, satisfies the above formulas (1) and (3). Regarding formula (2B), in the crystal, up to three lithium elements are coordinated to one phosphorus element, and up to four lithium elements are coordinated to one silicon element. Furthermore, in the crystal, lithium ions can bond with halide ions. In other words, the value of (Li-X) / (3P+4Si) in formula (2B) above indicates the degree of ortho-composition, and when this value is sufficiently close to 1.00, it means that the solid electrolyte has a favorable composition close to the ortho-composition. In the solid electrolyte described in [2] above, similarly to the solid electrolyte described in [1] above, by satisfying the above formula (1) and the above formula (2B), the ionic conductivity is high and the generation of hydrogen sulfide is suppressed. In addition, by satisfying the above formula (3), it is presumed that the ionic conductivity is increased by containing a sufficient amount of halogen element.

[0020] [3] In the solid electrolyte described in [1] or [2] above, in an X-ray diffraction pattern using CuKα radiation, a diffraction peak A may be present in a diffraction angle 2θ range of 20.1°±0.3°, a diffraction peak B may be present in a diffraction angle 2θ range of 29.4°±0.3°, and a diffraction peak C may be present in a diffraction angle 2θ range of 33.3°±0.3°.

[0021] The crystalline phase characterized by the diffraction peaks A to C is a conventionally known sulfide solid electrolyte LGPS (Li １０ GeP ２ S １２ ) is a crystalline phase similar to the phase of LGPS. LGPS is a solid electrolyte with high ionic conductivity, and the solid electrolyte described in [3] above is thought to have higher ionic conductivity due to the precipitation of such a crystalline phase similar to LGPS. Furthermore, the solid electrolyte described in [3] above can be produced at a relatively low heat treatment temperature compared to LGPS, and has other advantages such as excellent productivity.

[0022] 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.

[0023] [4] In the solid electrolyte according to the above [3], in the X-ray diffraction diagram, there is no diffraction peak in the range of a diffraction angle 2θ of 24.9°±0.3°, or there is a diffraction peak D in the range of a diffraction angle 2θ of 24.9°±0.3° and the intensity I of the diffraction peak B is Ｂ The intensity I of the diffraction peak D relative to Ｄ Ratio I Ｄ / I Ｂ may be 0.50 or less.

[0024] The crystalline phase having the diffraction peak D is a crystalline phase with low ionic conductivity. The solid electrolyte described in [4] above has a higher ionic conductivity due to a smaller amount of the crystalline phase with low ionic conductivity, etc.

[0025] [5] In the solid electrolyte according to the above [3] or [4], in the X-ray diffraction diagram, the intensity I of the diffraction peak B Ｂ The intensity I of the diffraction peak C relative to Ｃ Ratio I Ｃ / I Ｂ may be 0.05 or more.

[0026] The solid electrolyte described in [5] above is considered to have a better crystal structure, and therefore has higher ionic conductivity and more suppresses the generation of hydrogen sulfide.

[0027] [6] In the solid electrolyte described in [1] above, the value of S / (P+Si) in the formula (2A) above may be 3.96 or less.

[0028] [7] In the solid electrolyte described in [2] above, the value of (Li-X) / (3P+4Si) in the formula (2B) above may be 0.98 or less.

[0029] The solid electrolyte described in the above [6] and the solid electrolyte described in the above [7] have higher ionic conductivity. Conventionally, sulfide solid electrolytes have tended to be basically searched for compositions based on ortho-compositions, and pseudo-binary systems (Li ４ SiS ４ -Li ３ P.S. ４ , Li ４ GeS ４ -Li ３ P.S. ４ , Li ４ SnS ４ -Li ３ P.S. ４ etc.) and pseudo-ternary systems (Li ４ SiS ４ -Li ４ SnS ４ -Li ３ P.S. ４It has been reported that ionic conductivity is increased by using an ortho-composition as a standard in solid electrolytes containing phosphorus, silicon, and halogen elements. Based on this, the inventors predicted that the highest ionic conductivity would be exhibited in an ortho-composition, even for solid electrolytes containing phosphorus, silicon, and halogen elements. However, experimental verification surprisingly revealed that even higher ionic conductivity is exhibited not in an ortho-composition, but in compositions with relatively lower sulfur or lithium contents than in an ortho-composition. This defies conventional wisdom, and although the mechanism of action is not yet clear, it is thought that the presence of halogen elements has an effect, and that the presence of halogen elements changes the optimal composition.

[0030] [8] In the solid electrolyte according to any one of [1] to [7] above, a molar ratio ((Br+I) / X) of the total content of the bromine element and the iodine element to the content of the halogen element may be 0.80 or more.

[0031] The solid electrolyte described in the above [8] has higher ionic conductivity and is more effectively inhibited from generating hydrogen sulfide.

[0032] [9] The solid electrolyte according to any one of the above [1] to [8] may be represented by the composition formula of the following formula (I): Li ａ (P １－ｂ Si ｂ ) S ｃ X ｄ Z ｅ ... (I) (In formula (I), X is a halogen element including at least one of bromine and iodine. Z is at least one element other than Li, P, Si, S, and X. a, b, c, d, and e satisfy the following relationships: 3.30≦a≦4.10, 0.25≦b≦0.45, 3.75≦c≦4.03, 0.40≦d≦1.00, and 0.00≦e≦0.50, respectively.)

[0033] The solid electrolyte described in the above [9] has higher ionic conductivity and is more effectively inhibited from generating hydrogen sulfide.

[0034]

[10] In the solid electrolyte according to any one of [1] to [9] above, the ionic conductivity at 25°C may be 5.0 mS / cm or more.

[0035] The solid electrolyte described in the above

[10] has higher ionic conductivity.

[0036] The ionic conductivity of the solid electrolyte is determined by measuring AC impedance using the following method. In an argon atmosphere with a dew point of −50°C or less, 120 mg of sample powder of the solid electrolyte is placed in a powder molding machine with an inner diameter of 10 mm, and then uniaxially pressed at 10 MPa to 100 MPa using a hydraulic press. If it is difficult to prepare 120 mg of sample powder, less than 120 mg of sample powder may be placed. In this case, a powder molding machine with an inner diameter of less than 10 mm may be used. After releasing the pressure, 120 mg of SUS316L powder is placed on the top surface of the sample as a current collector, and then uniaxially pressed again at 10 MPa to 100 MPa using a hydraulic press. The SUS316L powder used has a mesh size of less than 100 mesh / inch. Next, 120 mg of SUS316L powder was placed on the underside of the sample as a current collector, and the sample was then uniaxially pressed at 360 MPa for 5 minutes to obtain a pellet for ionic conductivity measurement. This pellet for ionic conductivity measurement was inserted into a Hohsen HS cell, and AC impedance measurements were performed at a predetermined temperature. The results were plotted as a Nyquist plot. For solid electrolytes in which no arc component was observed in the Nyquist plot, the value on the real axis at the measurement point on the highest frequency side was taken as the resistance R. For solid electrolytes in which an arc component was observed in the Nyquist plot, the value on the real axis at the end point on the low frequency side of the arc was taken as the resistance R. The measurement conditions were an applied voltage amplitude of 20 mV, a frequency range of 1 MHz to 100 mHz, and a measurement temperature of 25°C. Furthermore, 240 mg of SUS316L powder was uniaxially pressed at 360 MPa for 5 minutes to obtain a SUS current collector pellet. Thereafter, the thicknesses of the pellet for measuring ionic conductivity and the SUS current collector pellet are measured using a micrometer, and then the thickness of the SUS current collector pellet is subtracted from the thickness of the pellet for measuring ionic conductivity to calculate the thickness L of the solid electrolyte sample. ２５(mS / cm) is a function of the resistance R (Ω), the thickness L (cm) of the solid electrolyte sample, and the area A (cm) of the solid electrolyte sample. ２ ) and calculate it by the following formula (A): ２５ =1000L / (RA)...(A)

[0037]

[11] In the solid electrolyte according to any one of [1] to

[10] above, the molar ratio (Li / (P+Si)) of the content of the lithium element to the total content of the phosphorus element and the silicon element may be 3.30 or more and 4.10 or less.

[0038]

[12] In the solid electrolyte according to any one of [1] to

[11] above, the molar ratio (Br / (P+Si)) of the content of the bromine element to the total content of the phosphorus element and the silicon element may be 0.05 or more.

[0039]

[13] In the solid electrolyte according to any one of [1] to

[12] above, the molar ratio (I / (P+Si)) of the content of the iodine element to the total content of the phosphorus element and the silicon element may be 0.05 or more.

[0040]

[14] In the solid electrolyte according to any one of [1] to

[13] 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 0.40 or more and 1.00 or less.

[0041]

[15] In the solid electrolyte according to any one of [1] to

[14] above, a molar ratio (Z / (P+Si)) of the content of an element (Z) other than the lithium element, the phosphorus element, the silicon element, the sulfur element, and the halogen element to the total content of the phosphorus element and the silicon element may be 0.00 or more and 0.50 or less.

[0042] The solid electrolyte according to any one of the above

[11] to

[15] is also a suitable embodiment of the present invention.

[0043]

[16] A method for producing a solid electrolyte according to one aspect of the present invention includes heat-treating a material for producing a solid electrolyte, wherein the material for producing a solid electrolyte contains lithium, phosphorus, silicon, sulfur, and a halogen element, the halogen element including at least one of bromine and iodine, and the elemental composition of the material for producing a solid electrolyte satisfies the following formulas (1), (2A), and (3): 0.25≦Si / (P+Si)≦0.45 (1) 3.75≦S / (P+Si)≦4.03 (2A) 0.40≦X / (P+Si) (3) (In formulas (1), (2A), and (3), P, Si, S, and X represent the molar contents of phosphorus, silicon, sulfur, and the halogen element in the material for producing a solid electrolyte, respectively.)

[0044]

[17] A method for producing a solid electrolyte according to one aspect of the present invention includes heat-treating a material for producing a solid electrolyte, wherein the material for producing a solid electrolyte contains lithium, phosphorus, silicon, sulfur, and a halogen element, the halogen element including at least one of bromine and iodine, and the elemental composition of the material for producing a solid electrolyte satisfies the following formulas (1), (2B), and (3): 0.25≦Si / (P+Si)≦0.45 (1) 0.86≦(Li−X) / (3P+4Si)≦1.02 (2B) 0.40≦X / (P+Si) (3) (In formulas (1), (2B), and (3), Li, P, Si, and X represent the molar contents of lithium, phosphorus, silicon, and the halogen element in the material for producing a solid electrolyte, respectively.)

[0045] According to the method for producing a solid electrolyte described in the above

[16] and the method for producing a solid electrolyte described in the above

[17] , a solid electrolyte having high ionic conductivity and suppressed generation of hydrogen sulfide can be produced.

[0046]

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

[15] above.

[0047] The electric storage element according to the above

[18] contains a solid electrolyte having high ionic conductivity and suppressing the generation of hydrogen sulfide, and therefore has good charge / discharge performance.

[0048] 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.

[0049] 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.

[0050] <Solid Electrolyte> (Composition) A solid electrolyte according to one embodiment of the present invention contains lithium, phosphorus, silicon, sulfur, and a halogen. The halogen includes at least one of bromine and iodine. The solid electrolyte refers to an electrolyte that remains solid at 25°C under a nitrogen atmosphere. The solid electrolyte preferably has lithium ion conductivity. The solid electrolyte may be a sulfide solid electrolyte.

[0051] The solid electrolyte has an elemental composition that satisfies the following formula (1), the following formula (2A) or the following formula (2B), and the following formula (3): 0.25≦Si / (P+Si)≦0.45 (1) 3.75≦S / (P+Si)≦4.03 (2A) 0.86≦(Li−X) / (3P+4Si)≦1.02 (2B) 0.40≦X / (P+Si) (3) In formulas (1), (2A), (2B), and (3), Li, P, Si, S, and X represent the molar contents of lithium, phosphorus, silicon, sulfur, and halogen elements in the solid electrolyte, respectively.

[0052] The lower limit of Si / (P+Si) in the above formula (1), i.e., the molar ratio of the content of silicon element to the total content of phosphorus element and silicon element (Si / (P+Si)), is 0.25, preferably 0.28, and more preferably 0.30. The upper limit of the molar ratio (Si / (P+Si)) is 0.45, preferably 0.42, and more preferably 0.40. When the molar ratio (Si / (P+Si)) is in the above range, it is possible to increase the ionic conductivity of the nonaqueous electrolyte and suppress the generation of hydrogen sulfide. The lower limit of the molar ratio (Si / (P+Si)) may be 0.32, 0.35, or 0.37. The upper limit of the molar ratio (Si / (P+Si)) may be 0.37, 0.35, or 0.32.

[0053] The lower limit of S / (P+Si) in the above formula (2A), i.e., the molar ratio of the sulfur content to the total content of phosphorus and silicon (S / (P+Si)), is 3.75, preferably 3.77, and more preferably 3.80. The upper limit of the molar ratio (S / (P+Si)) is 4.03, preferably 4.00, more preferably 3.96, and even more preferably 3.92. When the molar ratio (S / (P+Si)) is in the above range, the ionic conductivity of the nonaqueous electrolyte can be increased, and the generation of hydrogen sulfide can be suppressed. The lower limit of the molar ratio (S / (P+Si)) may be 3.82 or 3.85. The upper limit of the molar ratio (S / (P+Si)) may be 3.90, 3.87, or 3.85.

[0054] In the above formula (2B), (Li-X) / (3P+4Si), i.e., the molar ratio ((Li-X) / (3P+4Si)) of the lithium content minus the halogen content relative to the sum of three times the phosphorus content and four times the silicon content, has a lower limit of 0.86, preferably 0.87, and more preferably 0.88. The upper limit of the molar ratio ((Li-X) / (3P+4Si)) is 1.02, preferably 1.00, more preferably 0.98, and even more preferably 0.96. By having the molar ratio ((Li-X) / (3P+4Si)) in the above range, it is possible to increase the ionic conductivity of the nonaqueous electrolyte, suppress the generation of hydrogen sulfide, and the like. The lower limit of the molar ratio ((Li-X) / (3P+4Si)) may be 0.90. The upper limit of the molar ratio ((Li-X) / (3P+4Si)) may be 0.94 or 0.92.

[0055] The lower limit of X / (P+Si) in the above formula (3), i.e., the molar ratio of the content of halogen elements to the total content of phosphorus and silicon elements (X / (P+Si)), is 0.40, preferably 0.45, more preferably 0.48, and even more preferably 0.50. When the molar ratio (X / (P+Si)) is equal to or greater than the above lower limit, it is possible to increase the ionic conductivity of the non-aqueous electrolyte. The upper limit of the molar ratio (X / (P+Si)) is preferably 1.00, more preferably 0.80, and even more preferably 0.70, and may be 0.60, 0.55, or 0.50. When the molar ratio (X / (P+Si)) is equal to or less than the above upper limit, it is possible to further increase the ionic conductivity of the non-aqueous electrolyte.

[0056] In addition to the above, with regard to the constituent elements of the solid electrolyte, 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 3.30, more preferably 3.40, even more preferably 3.45, and even more preferably 3.50. When the molar ratio (Li / (P+Si)) is not less than the above lower limit, the ionic conductivity of the non-aqueous electrolyte can be further increased. The lower limit of the molar ratio (Li / (P+Si)) may be 3.55, 3.60, or 3.65. The upper limit of the molar ratio (Li / (P+Si)) is preferably 4.10, more preferably 4.00, even more preferably 3.95, and even more preferably 3.90. When the molar ratio (Li / (P+Si)) is not more than the above upper limit, the ionic conductivity of the non-aqueous electrolyte can be further increased. The upper limit of the molar ratio (Li / (P+Si)) may be 3.85, 3.80, 3.75, 3.70, 3.65, or 3.60.

[0057] The halogen element contained in the solid electrolyte includes at least one of bromine and iodine, and preferably includes both bromine and iodine, which can increase the ionic conductivity of the solid electrolyte.

[0058] The lower limit of the molar ratio ((Br+I) / X) of the total content of bromine and iodine elements to the content of halogen elements is preferably 0.80, more preferably 0.90, even more preferably 0.95, and even more preferably 0.99. When the content of halogen elements other than bromine and iodine elements is low in this way, the ionic conductivity of the solid electrolyte tends to be higher. The upper limit of the molar ratio ((Br+I) / X) may be 1.00. The molar ratio ((Br+I) / X) may be 1.00.

[0059] 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 0.05, more preferably 0.10, and even more preferably 0.20. The upper limit of the molar ratio (Br / (P+Si)) is preferably 0.80, more preferably 0.60, even more preferably 0.50, and even more preferably 0.40. When the molar ratio (Br / (P+Si)) is within the above range, the ionic conductivity of the nonaqueous electrolyte can be further increased.

[0060] The lower limit of the molar ratio (I / (P+Si)) of the content of iodine element to the total content of phosphorus element and silicon element is preferably 0.05, more preferably 0.10, even more preferably 0.15, and even more preferably 0.17. When the molar ratio (I / (P+Si)) is equal to or greater than the above lower limit, the ionic conductivity of the non-aqueous electrolyte can be further increased. Although the reason for this is unclear, it is presumed that the sufficient content of iodine element, which has a large ionic radius, causes a moderate distortion in the crystal structure, making it easier for lithium ions to move. The upper limit of the molar ratio (I / (P+Si)) is preferably 0.50, more preferably 0.40, even more preferably 0.30, and even more preferably 0.25.

[0061] The solid electrolyte may be substantially free of chlorine. The upper limit of the molar ratio of the content of chlorine to the total content of phosphorus and silicon (Cl / (P+Si)) is preferably 0.05, more preferably 0.02, and even more preferably 0.01. The molar ratio (Cl / (P+Si)) may be less than 0.01 or may be 0.00.

[0062] The solid electrolyte may be substantially free of elemental fluorine. The upper limit of the molar ratio of the content of elemental fluorine to the total content of elemental phosphorus and elemental silicon (F / (P+Si)) is preferably 0.05, more preferably 0.02, and even more preferably 0.01. The molar ratio (F / (P+Si)) may be less than 0.01 or may be 0.00.

[0063] The solid electrolyte may further contain an element (Z) other than lithium, phosphorus, silicon, sulfur, and halogen. The other element (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 element (Z) to the total content of phosphorus and silicon is preferably 0.50, more preferably 0.40, and even more preferably 0.30, 0.20, 0.10, 0.05, or 0.01. When the solid electrolyte does not contain the other element (Z) or the content of the other element (Z) is low, the essential elements can function effectively, thereby further increasing the ionic conductivity of the non-aqueous electrolyte and further suppressing the generation of hydrogen sulfide. The molar ratio (Z / (P+Si)) of the content of the other element (Z) to the total content of phosphorus and silicon may be less than 0.01 or may be 0.00. The lower limit of the molar ratio (Z / (P+Si)) may be 0.00.

[0064] The solid electrolyte may have a low content of nitrogen element as the other element (Z), or may not contain nitrogen element. The solid electrolyte may also 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.

[0065] The solid electrolyte may have a low content of oxygen element as the other element (Z), or may not contain oxygen element. The solid electrolyte may also 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.

[0066] The solid electrolyte is preferably represented by the composition formula (I) below: ａ (P １－ｂ Si ｂ ) S ｃ X ｄ Z ｅ ... (I) In formula (I), X is a halogen element including at least one of bromine and iodine. Z is at least one element other than Li, P, Si, S, and X. a, b, c, d, and e satisfy the following relationships: 3.30≦a≦4.10, 0.25≦b≦0.45, 3.75≦c≦4.03, 0.40≦d≦1.00, and 0.00≦e≦0.50, respectively.

[0067] When the solid electrolyte has the element composition represented by the above formula (I), the ionic conductivity is further increased and the generation of hydrogen sulfide is further suppressed. The preferred ranges of a, b, c, d, and e in the above formula (I) 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, and the preferred range of e is the same as the preferred range of the molar ratio (Z / (P+Si)) described above. The preferred ranges of the other contents in the solid electrolyte represented by the above formula (I) are also the same as the preferred ranges described above.

[0068] (Crystal Structure) The solid electrolyte according to one embodiment of the present invention preferably has, in an X-ray diffraction diagram using CuKα radiation, a diffraction peak A in a diffraction angle 2θ range of 20.1°±0.3°, a diffraction peak B in a diffraction angle 2θ range of 29.4°±0.3°, and a diffraction peak C in a diffraction angle 2θ range of 33.3°±0.3°. When the solid electrolyte has such a crystal structure, it is possible to further increase ionic conductivity, etc.

[0069] In the above X-ray diffraction diagram, the intensity I of the diffraction peak B Ｂ Intensity of diffraction peak C relative to I Ｃ Ratio IＣ / I Ｂ The lower limit of the ratio I is preferably 0.05, more preferably 0.07, and even more preferably 0.09, and may be 0.10, 0.15, or 0.20. Ｃ / I Ｂ When the ratio I is equal to or greater than the lower limit, the ionic conductivity of the non-aqueous electrolyte can be further increased. Ｃ / I Ｂ The upper limit of is preferably 0.60, more preferably 0.50, even more preferably 0.40, and even more preferably 0.30.

[0070] In the above X-ray diffraction diagram, the intensity I of the diffraction peak B Ｂ Intensity of diffraction peak A relative to I Ａ Ratio I Ａ / I Ｂ The lower limit of the ratio I is, for example, 0.10, and may be 0.15, 0.20, or 0.25. Ａ / I Ｂ The upper limit is, for example, 0.50, and may be 0.40, 0.30, or 0.25.

[0071] In the X-ray diffraction pattern, the diffraction peak B may be the highest diffraction peak in the diffraction angle 2θ range of 10.0° to 40.0°. That is, the intensity I of the diffraction peak B among the intensities of all the diffraction peaks in the range Ｂ may be the largest value.

[0072] In the X-ray diffraction pattern, there is no diffraction peak in the range of a diffraction angle 2θ of 24.9°±0.3°, or there is a diffraction peak D in the range of a diffraction angle 2θ of 24.9°±0.3° and the intensity I of the diffraction peak B is Ｂ The intensity I of the diffraction peak D relative to Ｄ Ratio I Ｄ / I Ｂ It is preferable that the ratio I is 0.50 or less. Ｄ / I Ｂ The upper limit of ratio I is preferably 0.45, more preferably 0.40, and even more preferably 0.35, 0.30, 0.25, 0.20, 0.15, 0.10 or 0.05. Ｄ / I ＢWhen the content of the nonaqueous electrolyte is equal to or less than the upper limit, the ionic conductivity of the nonaqueous electrolyte can be further increased.

[0073] In the X-ray diffraction diagram, of all the diffraction peaks present in the diffraction angle 2θ range of 10.0° to 40.0°, it is preferable that any one of the diffraction peaks A, B, and C has the highest peak intensity, and it is more preferable that the diffraction peak B has the highest peak intensity. In such a case, a crystalline phase similar to the above-mentioned LGPS exists as the main crystalline phase in the nonaqueous electrolyte, and the ionic conductivity of the nonaqueous electrolyte tends to be further increased.

[0074] Intensity I of other diffraction peaks other than the diffraction peak A, the diffraction peak B, and the diffraction peak C present in the range of diffraction angle 2θ from 10.0° to 40.0° in the X-ray diffraction pattern Ｏ are the intensities I of the diffraction peak B. Ｂ In such a case, the non-aqueous electrolyte contains a crystalline phase similar to the above-described LGPS as the main crystalline phase, and the ionic conductivity of the non-aqueous electrolyte tends to be further increased. Ｂ Intensity I of the other diffraction peaks Ｏ Ratio I Ｏ / I Ｂ The upper limit may be 0.40 or 0.30.

[0075] (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 5.0 mS / cm, more preferably 5.5 mS / cm, and even more preferably 6.0 mS / cm, 6.6 mS / cm, 7.0 mS / cm, 7.5 mS / cm, 8.0 mS / cm, 8.5 mS / cm, 9.0 mS / cm, or 9.5 mS / cm. When the ionic conductivity of the solid electrolyte at 25°C is equal to or greater than the lower limit, the charge / discharge performance of an energy storage device including the solid electrolyte can be improved. The upper limit of the ionic conductivity is not particularly limited, but may be, for example, 20 mS / cm, 15 mS / cm, or 12 mS / cm.

[0076] 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.

[0077] <Method for Producing a Solid Electrolyte> A method for producing a solid electrolyte according to one embodiment of the present invention comprises heat treating a material for producing a solid electrolyte.

[0078] The material for producing a solid electrolyte contains lithium, phosphorus, silicon, sulfur, and a halogen element, and the halogen element includes at least one of bromine and iodine. The elemental composition of the material for producing a solid electrolyte satisfies the following formula (1), the following formula (2A) or the following formula (2B), and the following formula (3): 0.25≦Si / (P+Si)≦0.45 (1) 3.75≦S / (P+Si)≦4.03 (2A) 0.86≦(Li−X) / (3P+4Si)≦1.02 (2B) 0.40≦X / (P+Si) (3) In formulas (1), (2A), (2B) and (3), Li, P, Si, S and X represent the molar contents of lithium, phosphorus, silicon, sulfur and halogen elements in the material for producing a solid electrolyte, respectively.

[0079] 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.

[0080] 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.

[0081] Examples of compounds containing lithium include Li ２ S., Li. ２ O, Li ３ N., Li. ２ CO ３ , metallic lithium, LiBr, LiI, etc. Among these, Li ２ S, LiBr and LiI are preferred. The lithium element-containing compounds may be used alone or in combination of two or more.

[0082] 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.

[0083] Examples of compounds containing silicon include SiS, SiS ２ , SiO ２, and compounds containing silicon such as silicon element. ２ The silicon-containing compound may be used alone or in combination of two or more.

[0084] Examples of compounds containing sulfur include Li ２ S, P ２ S ３ , P ２ S ５ , Al ２ S ３ , MgS, SiS, SiS ２ 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.

[0085] Examples of compounds containing halogen elements include lithium halides and simple halogens. Specific examples of compounds containing halogen elements include LiBr and Br. ２ compounds containing bromine such as LiI, I ２ Among these, LiI and LiBr are preferred. The halogen-containing compounds may be used alone or in combination of two or more.

[0086] 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.

[0087] 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 consisting of lithium, phosphorus, silicon, sulfur, and halogen elements, which has been subjected to a process such as mechanical milling.

[0088] 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.

[0089] 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.

[0090] In a method for producing a solid electrolyte according to an embodiment of the present invention, the heat treatment is preferably performed by raising the temperature to a maximum heat treatment temperature set in the temperature range of 280°C to 360°C and maintaining the temperature. In this production method, by performing heat treatment on a material for producing a solid electrolyte by raising the temperature to a maximum heat treatment temperature set in the above temperature range and maintaining the temperature, a solid electrolyte having high ionic conductivity and in which a crystalline phase similar to the above-mentioned LGPS is sufficiently precipitated is easily obtained. The heat treatment may be performed under a reduced pressure atmosphere or an inert gas atmosphere. The lower limit of the maximum heat treatment temperature is preferably 290°C, more preferably 300°C, and even more preferably 310°C. The upper limit of the maximum heat treatment temperature is more preferably 380°C, and may be 370°C or 360°C. The time for maintaining the maximum heat treatment temperature is preferably 1 hour to 24 hours, more preferably 2 hours to 12 hours. The upper limit of the time for maintaining the maximum heat treatment temperature may be 10 hours or 5 hours.

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

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

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

[0094] The energy storage device 1 contains a solid electrolyte according to an embodiment of the present invention in at least one of the positive electrode 2, the negative electrode 3, and the separator 4. More specifically, the solid electrolyte according to an embodiment of the present invention is contained in at least one of the positive electrode active material layer 6, the negative electrode active material layer 8, and the separator 4. The energy storage device 1 contains a solid electrolyte that has high ionic conductivity and suppresses the generation of hydrogen sulfide, and therefore has good charge / discharge performance.

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

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

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

[0098] Examples of sulfide solid electrolytes other than the solid electrolyte according to one embodiment of the present invention include Li ２ S-P ２ S５ 、i ２ 3-0 ２ ﳳ ５ -iｩ、ｬi ２ 3-0 ２ ﳳ ５ -iCl、ｬi ２ 3-0 ２ ﳳ ５ -iBr、ｬi ２ 3-0 ２ ﳳ ５ -i ２ 9、i ２ 3-0 ２ ﳳ ５ -i ２ OLiｩ、ii ２ 3-0 ２ ﳳ ５ -i ３ N、ii ２ 3-3iｳ ２ 、i ２ 3-3iｳ ２ -iｩ、ｬi ２ 3-3iｳ ２ -iBr、ｬi ２ 3-3iｳ ２ -iCl、ｬi ２ 3-3iｳ ２ -3 ２ ﳳ ３ -iｩ、ｬi ２ 3-3iｳ ２ -P ２ ﳳ ５ -iｩ、ｬi ２ 3-3 ２ ﳳ ３ 、i ２ 3-0 ２ ﳳ ５ -Z ｍ ﳳ ２ｎ ```````````````````````````````(``````(``````````‘``‘`‘`‘‘`‘‘‘`‘‘``‘````````````````````````````````````````````````````(tom? alive? ２ 3-11⁄3 ２ 、i ２ 3-3iｳ ２ -i ３ PO ４ 、i ２ 3-3iｳ ２ -i ｘ 79 ｙ(where x and y are positive numbers, and M is one of P, Si, Ge, B, Al, Ga, and In.), Li １０ GeP ２ S １２ etc.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

[0117] The positive electrode active material is usually particulate. The average particle size of the positive electrode active material is preferably, for example, 0.1 μm or more and 20 μm or less. By setting the average particle size of the positive electrode active material to the above-mentioned lower limit or more, the production and handling of the positive electrode active material becomes easier. By setting the average particle size of the positive electrode active material to the above-mentioned upper limit or less, the electronic conductivity of the positive electrode active material layer is improved. When a composite of the positive electrode active material and another material is used, the average particle size of the composite is taken as the average particle size of the positive electrode active material. The term "average particle size" refers to the value (D50) at which the volume-based cumulative distribution calculated in accordance with JIS-Z-8819-2 (2001) is 50% based on the particle size distribution measured by laser diffraction / scattering in accordance with JIS-Z-8825 (2013) for a diluted solution obtained by diluting particles with a solvent. For example, known methods using a pulverizer, a classifier, or the like can be used to obtain particles of the positive electrode active material and the negative electrode active material described below with a predetermined particle size.

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

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

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

[0121] When the solid electrolyte according to one embodiment of the present invention is used in the positive electrode active material layer, the content of the solid electrolyte according to one embodiment of the present invention relative to the total solid electrolyte in the positive electrode active material layer is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, and even more preferably substantially 100% by mass. 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 in the positive electrode active material layer is preferably 5% by mass or more and 90% by mass or less, and more preferably 20% by mass or more and 70% by mass or less.

[0122] The conductive agent is usually a component made of a material having electrical conductivity. Even when the volume resistivity of the conductive agent cannot be measured directly, it is possible to measure the volume resistivity by measuring the volume resistivity of the conductive agent when the volume resistivity is 10 －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 kinds. The conductive agent may be a composite of these materials. For example, a composite material of carbon black and CNT may be used.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

[0139] The negative electrode active material layer includes a negative electrode active material. The negative electrode active material layer may optionally include optional components such as a solid electrolyte, a conductive agent, a binder, a thickener, and a filler. The 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.

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

[0141] "Graphite" refers to a graphite material that has an average lattice spacing (d ００２ ) is 0.33 nm or more and less than 0.34 nm. Examples of graphite include natural graphite and artificial graphite.

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

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

[0144] The negative electrode active material may be particulate. The average particle size of the negative electrode active material may be, for example, 1 nm or more and 100 μm or less. When the negative electrode active material is a carbon material, a titanium-containing oxide, a polyphosphate compound, or the like, the average particle size may be 1 μm or more and 100 μm or less. When the negative electrode active material is Si, Sn, Si oxide, Sn oxide, or the like, the average particle size may be 1 nm or more and 1 μm or less. By setting the average particle size of the negative electrode active material to be equal to or greater than the above lower limit, the production or handling of the negative electrode active material becomes easier. By setting the average particle size of the negative electrode active material to be equal to or less than the above upper limit, the electronic conductivity of the negative electrode active material layer is improved.

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

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

[0147] When the negative electrode active material layer contains a conductive agent, the content of the conductive agent in the negative electrode active material layer is preferably 1% by mass or more and 10% by mass or less, and more preferably 3% by mass or more and 9% by mass or less. The content of the conductive agent in the negative electrode active material layer may be 5% by mass or less, or may be 2% by mass or less. The technology disclosed herein may also be implemented in an embodiment in which the negative electrode active material layer does not contain a conductive agent.

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

[0149] When the solid electrolyte according to one embodiment of the present invention is used in the negative electrode active material layer, the content of the solid electrolyte according to one embodiment of the present invention relative to the total solid electrolyte in the negative electrode active material layer is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, and even more preferably substantially 100% by mass. 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 in the negative electrode active material layer is preferably 5% by mass or more and 90% by mass or less, and more preferably 20% by mass or more and 70% by mass or less.

[0150] In the negative electrode active material layer, the solid electrolyte may form a complex with the negative electrode active material. Such a complex may further contain other components (e.g., a conductive agent) in addition to the solid electrolyte and the negative electrode active material.

[0151] 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.

[0152] 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.

[0153] 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.

[0154] 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.

[0155] The thickness of the negative electrode active material layer is appropriately set depending on the type of negative electrode active material, the application of the energy storage device, and the like. The average thickness of one negative electrode active material layer may be, for example, 5 μm or more and 1,000 μm or less. The lower limit of the average thickness of one negative electrode active material layer may be 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, or 100 μm. The upper limit of the average thickness of one negative electrode active material layer may be 800 μm, 500 μm, 200 μm, 100 μm, 80 μm, 60 μm, or 40 μm. The mass per unit area of ​​one negative electrode active material layer is, for example, 2 mg / cm. ２ 50mg / cm or more ２ The lower limit of the mass per unit area of ​​one negative electrode active material layer may be 3 mg / cm or less. ２ , 4 mg / cm ２ , 5 mg / cm ２ or 6 mg / cm ２ The upper limit of the mass per unit area of ​​one negative electrode active material layer is 30 mg / cm ２ , 20 mg / cm ２ , 15 mg / cm ２ , 12 mg / cm ２ or 10 mg / cm ２ may be.

[0156] (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.

[0157] When the solid electrolyte according to one embodiment of the present invention is used in the separator, the content of the solid electrolyte according to one embodiment of the present invention relative to the total solid electrolyte in the separator 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. When the solid electrolyte according to one embodiment of the present invention is used in the separator, the content of the solid electrolyte according to one embodiment of the present invention in the separator is preferably 70% by mass or more, more preferably 90% by mass or more, even more preferably 99% by mass or more, and even more preferably substantially 100% by mass.

[0158] The isolation layer may contain an additive (e.g., Li ３ P.O. ４ The separator 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. When the separator contains a solid electrolyte and a binder, the separator may be formed by coating and drying a composition containing the above-mentioned components and an organic solvent.

[0159] 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.

[0160] (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.

[0161] 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.

[0162] (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.

[0163] 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.

[0164] 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.

[0165] 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.

[0166] <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.

[0167] 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.

[0168] 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.

[0169] 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.

[0170] 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.

[0171] 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.

[0172] 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.

[0173] <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.

[0174] 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.

[0175] 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.

[0176] EXAMPLES 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. Note that hereinafter, silicon element and tin element will also be referred to as element M.

[0177] [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 to 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, and halogen elements (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.

[0178] [Examples 2 to 5, Comparative Examples 1 to 7] The compounds used as raw materials and the amounts (molar ratios) thereof 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 5 and Comparative Examples 1 to 7 were obtained in the same manner as in Example 1.

[0179] Regarding the constituent elements of each solid electrolyte of the examples and comparative examples, the type of element M (silicon element (Si) or tin element (Sn)), the molar ratio of the content of lithium element to the total content of phosphorus element and element M (Li / (P+M)), the molar ratio of the content of sulfur element to the total content of phosphorus element and element M (S / (P+M)), the molar ratio of the content of bromine element to the total content of phosphorus element and element M (Br / (P+M)), the molar ratio of the content of iodine element to the total content of phosphorus element and element M (I / (P+M)), Table 1 shows the molar ratio of the halogen content to the total content of phosphorus and element M (X / (P+M)), the molar ratio of the phosphorus content to the total content of phosphorus and element M (P / (P+M)), the molar ratio of the M content to the total content of phosphorus and element M (M / (P+M)), and the molar ratio ((Li-X) / (3P+4M)) of the lithium content minus the halogen content to the sum of three times the phosphorus content and four times the silicon content. Note that each solid electrolyte in the examples and comparative examples can be considered to contain substantially no elements other than lithium, phosphorus, element M (silicon or tin), sulfur, and halogen (bromine and iodine). That is, for example, the composition formula of the solid electrolyte in Example 1 is Li ３．５０ (P ０．７０ Si ０．３０ ) S ３．８５ Br ０．３０ I ０．２０ is.

[0180] (X-ray Diffraction Measurement) For each solid electrolyte of the Examples and Comparative Examples, powder X-ray diffraction measurement was performed using the method described above to obtain an X-ray diffraction diagram. Each solid electrolyte had a diffraction peak A in the diffraction angle 2θ range of 20.1°±0.3°, a diffraction peak B in the diffraction angle 2θ range of 29.4°±0.3°, and a diffraction peak C in the diffraction angle 2θ range of 33.3°±0.3°. Note that, for each solid electrolyte of the Examples, of all the diffraction peaks present in the diffraction angle 2θ range of 10.0° to 40.0°, diffraction peak B was the diffraction peak with the highest peak intensity. FIG. 3 shows the X-ray diffraction patterns of the solid electrolytes of Examples 1, 3 and Comparative Example 4 (solid electrolytes with a molar ratio (Si / (P+Si)) of 0.30). FIG. 4 shows the X-ray diffraction patterns of the solid electrolytes of Examples 2, 4 and 5 (solid electrolytes with a molar ratio (Si / (P+Si)) of 0.40). Table 1 shows the I calculated based on the obtained X-ray diffraction patterns. Ｃ / I Ｂ (Intensity I of diffraction peak B Ｂ Intensity of diffraction peak C relative to I Ｃ (ratio of) and I Ｄ / I Ｂ (Intensity I of diffraction peak B Ｂ Intensity I of diffraction peak D Ｄ The ratio of the diffraction peak D to the diffraction peak D is shown. Ｄ / I Ｂ The column is marked "-".

[0181] [Evaluation] (Measurement of Ionic Conductivity) The ionic conductivity (σ) of each solid electrolyte of the Examples and Comparative Examples at 25°C was measured. ２５ ) was determined by measuring AC impedance using Bio-Logic's VMP-300 in the same manner as above. The ionic conductivity (σ ２５ ) are shown in Table 1.

[0182] (Amount of Hydrogen Sulfide Generated) For each of the solid electrolytes in Examples 1 to 5 and Comparative Examples 2 to 7, hydrogen sulfide (H ２The amount of generated CO₂ was measured. A desiccator was placed in a dry box with a dry air atmosphere at a dew point of −35°C. Then, the solid electrolyte powder (300 mg) was placed in a sealed desiccator (effective volume 2300 cm). ３ ) for 1 hour, and the hydrogen sulfide measurement was performed using a hydrogen sulfide measuring instrument (ToxiRAE Pro (H ２ The amount of hydrogen sulfide generated was measured using a 3P+4Si solid electrolyte (Li-X) / (3P+4Si) solution. The measurement results are shown in Table 1. FIG. 5 shows a scatter diagram for each of the solid electrolytes of Examples 1 to 5 and Comparative Examples 2 to 5 (solid electrolytes in which element M was silicon and the amount of hydrogen sulfide generated was measured), plotted on the horizontal axis as Si / (P+Si) in the above formula (1) and on the vertical axis as S / (P+Si) in the above formula (2A), and indicating the amount of hydrogen sulfide generated (ppm) for the corresponding solid electrolyte. FIG. 6 shows a scatter diagram for each of the solid electrolytes of Examples 1 to 5 and Comparative Examples 2 to 5, plotted on the horizontal axis as Si / (P+Si) in the above formula (1) and on the vertical axis as (Li-X) / (3P+4Si) in the above formula (2B), and indicating the amount of hydrogen sulfide generated (ppm) for the corresponding solid electrolyte.

[0183]

[0184] As shown in Table 1, Figures 5 and 6, in the solid electrolytes of the Examples which satisfy the above formula (1) and the above formula (2A) or (2B), i.e., 0.25≦Si / (P+Si)≦0.45 and 3.75≦S / (P+Si)≦4.03 or 0.86≦(Li−X) / (3P+4Si)≦1.02, the amount of hydrogen sulfide generated was 20 ppm or less, and the generation of hydrogen sulfide was suppressed. Furthermore, as shown in Table 1, the solid electrolytes of Comparative Example 1 which does not satisfy the above formula (3), i.e., the molar ratio (X / (P+Si)) is less than 0.40, and Comparative Examples 6 and 7 in which the element M is tin, have a higher ionic conductivity (σ) at 25°C than the solid electrolytes of the Examples. ２５ In contrast, the solid electrolytes of the examples that satisfied the above formula (1), the above formula (2A) or the above formula (2B), and the above formula (3) had high ionic conductivity and suppressed the generation of hydrogen sulfide.

[0185] 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.

[0186] REFERENCE SIGNS LIST 1 Energy storage element 2 Positive electrode 3 Negative electrode 4 Separator layer 5 Positive electrode substrate 6 Positive electrode active material layer 7 Negative electrode substrate 8 Negative electrode active material layer 20 Energy storage unit 30 Energy storage device

Claims

Contains lithium, phosphorus, silicon, sulfur and halogen elements, the halogen element includes at least one of a bromine element and an iodine element, A solid electrolyte satisfying the following formula (1), the following formula (2A), and the following formula (3). 0.25≦Si / (P+Si)≦0.45 (1) 3.75≦S / (P+Si)≦4.03...(2A) 0.40≦X / (P+Si)...(3) (In formulas (1), (2A), and (3), P, Si, S, and X represent the molar contents of phosphorus, silicon, sulfur, and halogen elements, respectively, in the solid electrolyte.) 　 Contains lithium, phosphorus, silicon, sulfur and halogen elements, the halogen element includes at least one of a bromine element and an iodine element, A solid electrolyte satisfying the following formula (1), the following formula (2B), and the following formula (3). 0.25≦Si / (P+Si)≦0.45 (1) 0.86≦(Li-X) / (3P+4Si)≦1.02...(2B) 0.40≦X / (P+Si)...(3) (In formula (1), formula (2B), and formula (3), Li, P, Si, and X represent the molar contents of lithium, phosphorus, silicon, and halogen elements in the solid electrolyte, respectively.) 　 3. The solid electrolyte according to claim 1, wherein an X-ray diffraction pattern using CuKα rays has a diffraction peak A in a diffraction angle 2θ range of 20.1°±0.3°, a diffraction peak B in a diffraction angle 2θ range of 29.4°±0.3°, and a diffraction peak C in a diffraction angle 2θ range of 33.3°±0.3°. 　 In the X-ray diffraction pattern, there is no diffraction peak in the range of a diffraction angle 2θ of 24.9°±0.3°, or there is a diffraction peak D in the range of a diffraction angle 2θ of 24.9°±0.3° and the intensity of the diffraction peak B is Ｂ The intensity I of the diffraction peak D relative to Ｄ Ratio I Ｄ / I Ｂ The solid electrolyte according to claim 3, wherein the σ is 0.50 or less. 　 In the X-ray diffraction diagram, the intensity I of the diffraction peak B Ｂ The intensity I of the diffraction peak C relative to Ｃ Ratio I Ｃ / I Ｂ The solid electrolyte according to claim 3, wherein is 0.05 or more.

2. The solid electrolyte according to claim 1, wherein the value of S / (P+Si) in the formula (2A) is 3.96 or less. 　 The solid electrolyte according to claim 2, wherein the value of (Li-X) / (3P+4Si) in the formula (2B) is 0.98 or less.

3. The solid electrolyte according to claim 1, wherein a molar ratio ((Br+I) / X) of the total content of said bromine element and said iodine element to the content of said halogen element is 0.80 or more.

3. The solid electrolyte according to claim 1 or 2, which is represented by the following composition formula (I): Li ａ (P) １－ｂ Yes ｂ )S ｃ X ｄ Z ｅ ・・・(@) (In formula (I), X is a halogen element including at least one of bromine and iodine. Z is at least one element other than Li, P, Si, S, and X. a, b, c, d, and e satisfy the following relationships: 3.30≦a≦4.10, 0.25≦b≦0.45, 3.75≦c≦4.03, 0.40≦d≦1.00, and 0.00≦e≦0.50, respectively.) 3. The solid electrolyte according to claim 1, wherein the ionic conductivity at 25°C is 5.0 mS / cm or more. 　 heat-treating a material for producing a solid electrolyte; The material for producing a solid electrolyte contains lithium, phosphorus, silicon, sulfur, and a halogen element, the halogen element includes at least one of a bromine element and an iodine element, The method for producing a solid electrolyte, wherein the elemental composition of the material for producing a solid electrolyte satisfies the following formula (1), the following formula (2A), and the following formula (3). 0.25≦Si / (P+Si)≦0.45 (1) 3.75≦S / (P+Si)≦4.03...(2A) 0.40≦X / (P+Si)...(3) (In the formulas (1), (2A), and (3), P, Si, S, and X represent the molar contents of phosphorus, silicon, sulfur, and halogen elements, respectively, in the material for producing a solid electrolyte.) 　 heat-treating a material for producing a solid electrolyte; The material for producing a solid electrolyte contains lithium, phosphorus, silicon, sulfur, and a halogen element, the halogen element includes at least one of a bromine element and an iodine element, The method for producing a solid electrolyte, wherein the elemental composition of the material for producing a solid electrolyte satisfies the following formula (1), the following formula (2B), and the following formula (3). 0.25≦Si / (P+Si)≦0.45 (1) 0.86≦(Li-X) / (3P+4Si)≦1.02...(2B) 0.40≦X / (P+Si)...(3) (In the formulas (1), (2B), and (3), Li, P, Si, and X represent the molar contents of lithium, phosphorus, silicon, and halogen elements, respectively, in the material for producing a solid electrolyte.) 　 An electric storage element comprising the solid electrolyte according to claim 1 or 2.

Images