JP2022030244A - Sulfide solid electrolyte, electricity storage element and method for producing sulfide solid electrolyte - Google Patents

Abstract

To provide a sulfide solid electrolyte that is excellent in ionic conductivity, an electricity storage element that contains a sulfide solid electrolyte excellent in ionic conductivity, and a method for producing a sulfide solid electrolyte excellent in ionic conductivity.SOLUTION: The sulfide solid electrolyte contains lithium, sulfur, phosphorus and chlorine, has a crystalline structure that has diffraction peaks at 2θ=17.8°±0.5°, 19.1°±0.5°, 21.7°±0.5°, 23.8°±0.5°, and 30.85°±0.5° in X-ray diffraction measurement using CuKα ray, and in which the valence of the phosphorus is 5, and the sulfide solid electrolyte has virtually no crystalline phase of β-Li3 PS4.SELECTED DRAWING: None

Description

The present invention relates to a sulfide solid electrolyte, a power storage element, and a method for producing a sulfide solid electrolyte.

Lithium-ion secondary batteries are widely used in personal computers, electronic devices such as communication terminals, automobiles, and the like because of their high energy density. The lithium ion secondary battery generally has a pair of electrodes electrically separated by a separator and a non-aqueous electrolyte interposed between the electrodes, and transfers lithium ions between the two electrodes. It is configured to charge and discharge. Further, as a power storage element other than a lithium ion secondary battery, a capacitor such as a lithium ion capacitor is also widely used.

In recent years, for the purpose of improving the safety of a non-aqueous electrolyte secondary battery, an all-solid-state battery has been proposed in which a sulfide solid electrolyte or the like is used as the non-aqueous electrolyte instead of a liquid electrolyte such as an organic solvent (Patent Documents). 1).

Japanese Unexamined Patent Publication No. 2000-340257

Sulfide solid electrolyte materials with further improved ion conductivity are desired for energy storage elements used in hybrid electric vehicles (hereinafter, also referred to as "HEV") and hybrid industrial machines (heavy machinery, construction machinery, etc.). ing.

The present invention has been made based on the above circumstances, and is a sulfide solid electrolyte having excellent ionic conductivity, a storage element containing a sulfide solid electrolyte having excellent ionic conductivity, and sulfide having excellent ionic conductivity. It is an object of the present invention to provide a method for producing a solid electrolyte.

One aspect of the present invention contains lithium, sulfur, phosphorus and chlorine, and 2θ = 17.8 ° ± 0.5 °, 19.1 ° ± 0.5 °, 21. It has a crystal structure with diffraction peaks at 7 ° ± 0.5 °, 23.8 ° ± 0.5 °, and 30.85 ° ± 0.5 °, and the valence of the phosphorus is pentavalent. It is a sulfide solid electrolyte having substantially no crystalline phase of β-Li ₃ PS ₄ .

Another aspect of the present invention is a power storage element containing a sulfide solid electrolyte according to one aspect of the present invention.

Another aspect of the present invention comprises heat-treating a sulfide glass containing lithium, sulfur, phosphorus and chlorine and having a pentavalent phosphorus valence, wherein the heat treatment temperature is the crystals of the sulfide glass. This is a method for producing a sulfide solid electrolyte, which is lower than the crystallization temperature and the difference between the crystallization temperature and the heat treatment temperature is 20 ° C. or higher and 45 ° C. or lower.

According to the sulfide solid electrolyte according to one aspect of the present invention, a sulfide solid electrolyte having excellent ionic conductivity, a power storage element containing a sulfide solid electrolyte having excellent ionic conductivity, and a sulfide solid electrolyte having excellent ionic conductivity. Production method can be provided.

FIG. 1 is a schematic cross-sectional view of an all-solid-state battery according to an embodiment of the power storage element of the present invention. FIG. 2 is a schematic view showing a power storage device configured by assembling a plurality of power storage elements according to an embodiment of the present invention. FIG. 3 is an X-ray diffraction pattern of each solid electrolyte of Example 2 to Example 4 and Comparative Example 2 to Comparative Example 4. FIG. 4 is an X-ray diffraction pattern of each solid electrolyte of Example 1, Example 3, Example 5 to Example 7, Comparative Example 1 and Comparative Example 5. FIG. 5 is an X-ray diffraction pattern of each solid electrolyte of Example 3, Comparative Example 6 and Reference Example.

The sulfide solid electrolyte according to one aspect of the present invention contains lithium, sulfur, phosphorus and chlorine, and 2θ = 17.8 ° ± 0.5 °, 19.1 ° ± 0 in X-ray diffraction measurement using CuKα ray. It has a crystal structure with diffraction peaks at .5 °, 21.7 ° ± 0.5 °, 23.8 ° ± 0.5 °, and 30.85 ° ± 0.5 °, and the valence of the above phosphorus. Is pentavalent and has substantially no crystalline phase of β-Li ₃ PS ₄ .

The present inventors have focused on the fact that chlorine among halogen atoms is superior in electrochemical stability to bromine and iodine in order to improve the battery performance of the power storage element. The chlorine-containing Li ₂ SP ₂ S ₅ -LiCl-based glass-ceramic solid electrolyte does not have a crystal structure with low ionic conductivity, but has a specific crystal structure, so that sulfide having excellent ionic conductivity is obtained. We thought that a solid electrolyte could be obtained, and came up with the present invention.
The sulfide solid electrolyte contains lithium, sulfur, pentavalent phosphorus and chlorine, has substantially no crystal phase of β _- Li ₃ PS4 having low ionic conductivity, and has high ionic conductivity. In X-ray diffraction measurement using CuKα ray considered to be a crystalline phase, 2θ = 17.8 ° ± 0.5 °, 19.1 ° ± 0.5 °, 21.7 ° ± 0.5 °, 23. Having a crystal structure having diffraction peaks at 8 ° ± 0.5 ° and 30.85 ° ± 0.5 ° is excellent in ionic conductivity.
In the present invention, "substantially free of the crystal phase of β-Li ₃ PS ₄ " means that the above crystal phase is not contained in the structure at all, and the detection limit in the X-ray diffraction measurement. The following cases are also included when the content ratio is low. In the above-mentioned "when it is below the detection limit in the X-ray diffraction measurement", it is below the detection limit in the X-ray diffraction measurement, but it is β _- Li 3PS in the observation with a transmission electron microscope (TEM). The case where the crystal phase of ₄ is detected is also included.

The sulfide solid electrolyte has the general formula (100-z) (yLi ₂ S · (1-y) P ₂ S ₅ ) · zLiCl · αM (provided, 0.74 ≦ y ≦ 0.78, 5 ≦ z ≦. 55, 0 ≦ α ≦ 30. M preferably has a composition represented by one or more elements other than Li, P, S and Cl). When the sulfide solid electrolyte has a composition represented by the above general formula, the ionic conductivity can be further enhanced.

The ionic conductivity of the sulfide solid electrolyte at 25 ° C. is preferably 6.0 × 10 ^-4 S / cm or more. When the ionic conductivity of the sulfide solid electrolyte at 25 ° C. is equal to or higher than the above value, the charge / discharge performance such as the high rate charge / discharge performance of the power storage element containing the sulfide solid electrolyte can be improved.

The power storage device according to another aspect of the present invention contains the sulfide solid electrolyte.

Since the power storage element according to another aspect of the present invention contains the sulfide solid electrolyte, it is excellent in ion conductivity and can improve charge / discharge performance such as high rate charge / discharge performance.

The method for producing a sulfide solid electrolyte according to another aspect of the present invention comprises heat-treating a sulfide glass containing lithium, sulfur, phosphorus and chlorine and having a valence of the phosphorus pentavalent. The temperature is lower than the crystallization temperature of the sulfide glass, and the difference between the crystallization temperature and the heat treatment temperature is 20 ° C. or higher and 45 ° C. or lower.

When the Li ₂ SP ₂ S ₅ -LiCl-based glass is heated, the crystal phase of β-Li ₃ PS ₄ , which is a phase with low ionic conductivity, is also deposited along with the precipitation of the crystal phase, which is a crystal phase with high ionic conductivity. Tends to precipitate. By heating the Li ₂ SP ₂ S ₅ -LiCl glass under certain conditions, the present inventors suppress the precipitation of the crystalline phase of β-Li ₃ PS ₄ , which is a phase having low ionic conductivity. It was found that the composition range in which a crystal phase with high ionic conductivity is deposited can be expanded. The method for producing the sulfide solid electrolyte comprises heat-treating the sulfide glass having the above composition, the temperature of the heat treatment is lower than the crystallization temperature of the sulfide glass, and the crystallization temperature and the heat treatment temperature are used. When the difference between the two is 20 ° C. or higher and 45 ° C. or lower, a sulfide solid electrolyte having a crystal phase having high ionic conductivity and having substantially no crystal phase of β-Li ₃ PS ₄ having low ionic conductivity can be obtained. Can be manufactured. Therefore, the production method can produce a sulfide solid electrolyte having excellent ionic conductivity.

In the Li ₂ SP ₂ S ₅ -LiCl glass, which is a raw material used in the method for producing the sulfide solid electrolyte, the valence of phosphorus (P) is +5. Therefore, in the sulfide glass having the above composition, it is considered that the PS ₄₃ ^- unit is the main skeleton as in the Li ₂ SP ₂ S ₅ series glass. When this sulfide glass is heat-treated at a temperature higher than the crystallization temperature of the sulfide glass, it is presumed that the phase transition is likely to occur in the β _{-Li 3 PS 4} ^phase _, which is also composed of PS ₄₃ -units. On the other hand, sulfide glass produced by using phosphorus having a valence other than +5-valent, such as 0-valent or +3-valent as a raw material, can be produced by P2 _S64 ^{-units in addition to PS4 3 -} _{units .} It is known (Solid State Inics 262 (2014) 733-737, JP-A-2018-174130, etc.). When this sulfide glass is heat-treated, it is presumed that the phase transition to the β-Li _{3PS 4 phase} is less likely to occur even under high temperature conditions, and the phase changes to other crystalline phases. Therefore, the phenomenon that β-Li ₃ PS ₄ phase is generated when heat-treated at a temperature higher than the crystallization temperature of sulfide glass is that the valence of phosphorus contained in sulfide glass, which is the raw material of sulfide solid electrolyte, is high. It is presumed to be remarkable when it has substantially only +5 valence.

The sulfide glass has a general formula (yLi ₂ S · (1-y) P ₂ S ₅ ) · zLiCl · αM (provided that 0.74 ≦ y ≦ 0.78, 5 ≦ z ≦ 55, 0 ≦ α ≦ 30. M preferably has a composition represented by one or more elements other than Li, P, S, and Cl). When the sulfide glass has a composition represented by the above general formula, a sulfide solid electrolyte having higher ionic conductivity can be produced.

Hereinafter, embodiments of the sulfide solid electrolyte and the all-solid-state battery according to the present invention will be described in detail.

<Sulfide solid electrolyte>
The sulfide solid electrolyte according to one aspect of the present invention contains lithium, sulfur, phosphorus and chlorine, and 2θ = 17.8 ° ± 0.5 °, 19.1 ° ± 0 in X-ray diffraction measurement using CuKα ray. A crystal structure having diffraction peaks at .5 °, 21.7 ° ± 0.5 °, 23.8 ° ± 0.5 °, and 30.85 ° ± 0.5 ° (hereinafter, also referred to as crystal phase A). ), The phosphorus has a valence of pentavalent, and is a sulfide solid electrolyte having substantially no crystal phase of β-Li ₃ PS ₄ . The sulfide solid electrolyte can be used in any application that requires excellent ionic conductivity. Above all, the sulfide solid electrolyte is preferably used for a lithium power storage element.

The sulfide solid electrolyte contains lithium, sulfur, phosphorus and chlorine and has a crystal structure. Further, the valence of phosphorus is pentavalent. Here, "having a crystal structure" means that a peak derived from the crystal structure of the sulfide solid electrolyte is observed in the X-ray diffraction pattern in the X-ray diffraction measurement. The sulfide solid electrolyte having a crystal structure can be obtained, for example, by crystallizing an amorphous sulfide glass solid electrolyte by heat treatment or the like.

The sulfide solid electrolyte does not substantially have a crystal phase of β _- Li ₃ PS4 having low ionic conductivity, and is considered to be a crystal phase having high ionic conductivity in X-ray diffraction measurement using CuKα rays. 2θ = 17.8 ° ± 0.5 °, 19.1 ° ± 0.5 °, 21.7 ° ± 0.5 °, 23.8 ° ± 0.5 °, and 30.85 ° ± 0. Having a crystal structure having a diffraction peak at 5 ° is excellent in ionic conductivity.

The diffraction peak in the first crystal structure may be in the range of 2θ, further in the range of ± 0.3 °, or in the range of ± 0.1 °.

The crystal phase of β-Li ₃ PS ₄ is the same as the crystal phase reported in Electrochemistry Communications 5 (2003) 111-114, and 2θ = 17.5 in the X-ray diffraction measurement using the CuKα ray. Diffracted at positions of ° ± 0.5 °, 18.6 ° ± 0.5 °, 29.1 ° ± 0.5 °, 29.9 ° ± 0.5 °, 31.2 ° ± 0.5 ° Has a peak.
Therefore, the sulfide solid electrolyte does not have the diffraction peak identified in the crystal phase of β-Li ₃ PS ₄ in the X-ray diffraction diagram using CuKα ray.

The X-ray diffraction measurement using the CuKα ray is performed by the following procedure. The airtight sample holder for X-ray diffraction measurement is filled with the solid electrolyte powder to be measured under an argon atmosphere having a dew point of −50 ° C. or lower. Powder X-ray diffraction measurement is performed using an X-ray diffractometer (“MiniFlex II” manufactured by Rigaku). The radiation source is CuKα ray, the tube voltage is 30 kV, the tube current is 15 mA, and the diffracted X-ray is detected by a high-speed one-dimensional detector (model number: D / teX Ultra 2) through a Kβ filter having a thickness of 30 μm. The sampling width is 0.01 °, the scan speed is 5 ° / min, the divergent slit width is 0.625 °, the light receiving slit width is 13 mm (OPEN), and the scattering slit width is 8 mm.

As the sulfide solid electrolyte, the sulfide glass is of the general formula (100-z) (yLi ₂ S · (1-y) P ₂ S ₅ ) · zLiCl · αM (where 0.74 ≦ y ≦ 0. 78, 5 ≦ z ≦ 55, 0 ≦ α ≦ 30. M preferably has a composition represented by one or more elements other than Li, P, S, and Cl). When the sulfide solid electrolyte has a composition represented by the above general formula, the ionic conductivity can be further enhanced.

As the lower limit of z in the above general formula, 10 is preferable, 12 is more preferable, and 15 is further preferable. As the upper limit of z, 50 is preferable, 40 is more preferable, and 30 is further preferable. When z in the above general formula is in the above range, the ionic conductivity at 25 ° C. can be further increased.

The lower limit of y in the above general formula is preferably 0.75. The upper limit of y is preferably 0.77. When the content ratio of Li ₂ S and P ₂ S ₅ in the sulfide solid electrolyte is in the above range, it has high ionic conductivity.

As α in the above general formula, 0 is preferable. When α = 0 in the above general formula, the ionic conductivity can be further improved.

Examples of the element M in the above general formula include elements belonging to any of the second to fifth periods of the 13th to 17th groups of the periodic table. Among these, N, O, F, Br and I are preferable. When the element M in the above general formula is an element belonging to any of the above ranges in the periodic table, the performance such as water resistance, reduction resistance, and ion conductivity can be improved.

The lower limit of the ionic conductivity of the sulfide solid electrolyte at 25 ° C. is preferably 6.0 × 10 ^-4 S / cm, more preferably 8.0 × 10 ^-4 S / cm, and 9.0 × 10 ⁻ . ⁴ S / cm is more preferable, and 1.0 × 10 ^-3 S / cm is particularly preferable. When the ionic conductivity of the sulfide solid electrolyte at 25 ° C. is equal to or higher than the above value, the charge / discharge performance such as the high rate charge / discharge performance of the power storage element can be improved.

The ionic conductivity of the sulfide solid electrolyte is determined by measuring the AC impedance by the following method. In an argon atmosphere with a dew point of −50 ° C. or lower, 120 mg of sample powder is put into a powder molding machine having an inner diameter of 10 mm, and then uniaxial pressure molding is performed at 50 MPa or less using a hydraulic press. After the pressure is released, 120 mg of SUS316L powder is charged onto the upper surface of the sample as a current collector, and then uniaxial pressure molding is performed again using a hydraulic press at 50 MPa or less. Next, 120 mg of SUS316L powder as a current collector is charged on the lower surface of the sample, and then 360 MPa, 5 min uniaxial pressure molding is performed to obtain pellets for ion conductivity measurement. The pellet for measuring ionic conductivity is inserted into an HS cell manufactured by Hosen Co., Ltd., and AC impedance is measured under a predetermined temperature. The measurement conditions are an applied voltage amplitude of 20 mV, a frequency range of 1 MHz to 100 MHz, and a measurement temperature of 25 ° C.

The ratio of the lithium content (Li / Cl) to the chlorine content is preferably less than 16.0 and 1.5 or more in terms of molar ratio. By setting the ratio of the lithium content (Li / Cl) to the chlorine content in the above range, a crystal phase having high ionic conductivity tends to be easily precipitated, and the ionic conductivity tends to be enhanced.

The ratio (S / Cl) of the sulfur content to the chlorine content is preferably less than 19.0 and 2.0 or more in terms of molar ratio. By setting the ratio of the lithium content (Li / Cl) to the chlorine content in the above range, a crystal phase having high ionic conductivity tends to be easily precipitated, and the ionic conductivity tends to be enhanced.

The shape of the solid electrolyte is not particularly limited, and is usually granular, lumpy, or the like.

According to the sulfide solid electrolyte, the ionic conductivity is excellent. The sulfide solid electrolyte can be suitably used as an electrolyte for a power storage element such as a lithium ion secondary battery, particularly a lithium ion power storage element. Above all, it can be particularly preferably used as an electrolyte for an all-solid-state battery. The solid electrolyte can be used for any of the positive electrode layer, the isolation layer, the negative electrode layer and the like in the power storage element.

<Power storage element>
Hereinafter, as an embodiment of the power storage element of the present invention, an all-solid-state battery will be described as a specific example. The power storage element 10 shown in FIG. 1 is an all-solid-state battery, and is a secondary battery in which a positive electrode layer 1 and a negative electrode layer 2 are arranged via an isolation layer 3. The positive electrode layer 1 has a positive electrode base material 4 and a positive electrode active material layer 5, and the positive electrode base material 4 is the outermost layer of the positive electrode layer 1. The negative electrode layer 2 has a negative electrode base material 7 and a negative electrode active material layer 6, and the negative electrode base material 7 is the outermost layer of the negative electrode layer 2. In the power storage element 10 shown in FIG. 1, the negative electrode active material layer 6, the isolation layer 3, the positive electrode active material layer 5, and the positive electrode base material 4 are laminated in this order on the negative electrode base material 7.

The power storage element 10 contains a sulfide solid electrolyte according to an embodiment of the present invention in at least one of the positive electrode layer 1, the negative electrode layer 2, and the isolation layer 3. More specifically, at least one of the positive electrode active material layer 5, the negative electrode active material layer 6 and the isolation layer 3 contains the solid electrolyte according to the embodiment of the present invention. Since the power storage element 10 contains the sulfide solid electrolyte having excellent ionic conductivity, it is excellent in ionic conductivity and can improve charge / discharge performance such as high rate charge / discharge performance.

The power storage element 10 may also use a solid electrolyte other than the solid electrolyte according to the embodiment of the present invention. Examples of other solid electrolytes include sulfide solid electrolytes other than the sulfide solid electrolyte, oxide-based solid electrolytes, dry polymer electrolytes, gel polymer electrolytes, pseudo-solid electrolytes, and the like, and sulfide solid electrolytes are preferable. Further, a plurality of different types of solid electrolytes may be contained in one layer of the power storage element 10, and different solid electrolytes may be contained in each layer.

Examples of the sulfide solid electrolyte include Li ₂ SP ₂ S ₅ , Li ₂ SP ₂ S ₅ -LiI, Li ₂ SP ₂ S ₅ -LiCl, Li ₂ SP ₂ S ₅ -LiBr, and the like. Li ₂ S-P ₂ S ₅ -Li ₂ O, Li ₂ S-P ₂ S ₅ -Li ₂ O-Li I, Li ₂ S-P ₂ S ₅ -Li ₃ N, Li ₂ S-SiS ₂ , Li ₂ S-SiS ₂ -LiI, Li ₂ S-SiS ₂ -LiBr, Li ₂ S-SiS ₂ -LiCl, Li ₂ S-SiS ₂ -B ₂ S ₃ -LiI, Li ₂ S-SiS ₂ -P ₂ S ₅ -LiI, Li ₂ SB ₂ S ₃ , Li ₂ SP ₂ S ₅ -Z _m S _2n (where m and n are positive numbers and Z is any of Ge, Zn and Ga. ), Li ₂ S-GeS ₂ , Li ₂ S-SiS ₂ -Li ₃ PO ₄ , Li ₂ S-SiS ₂ -Li _x MO _y (where x, y are positive numbers, M is P, Si, It is any of Ge, B, Al, Ga, In), Li ₁₀ GeP ₂ S ₁₂ , and the like.

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

(Positive electrode base material)
The positive electrode base material 4 has conductivity. Having "conductive" means that the volume resistivity measured according to JIS-H-0505 (1975) is ¹⁰⁷ Ω · cm or less, and "non-conductive" means. It means that the volume resistivity is more than ¹⁰⁷ Ω · cm. As the material of the positive electrode base material 4, a metal such as aluminum, titanium, tantalum, indium, stainless steel or an alloy thereof or an alloy thereof is used. Among these, aluminum or an aluminum alloy is preferable from the viewpoint of potential resistance, high conductivity, and cost. Examples of the positive electrode base material 4 include a foil and a vapor-deposited film, and the foil is preferable from the viewpoint of cost. Therefore, aluminum foil or aluminum alloy foil is preferable as the positive electrode base material 4. Examples of aluminum or aluminum alloy include A1085P and A3003P specified in JIS-H-4000 (2014).

The average thickness of the positive electrode substrate 4 is preferably 3 μm or more and 50 μm or less, more preferably 5 μm or more and 40 μm or less, further preferably 8 μm or more and 30 μm or less, and particularly preferably 10 μm or more and 25 μm or less. By setting the average thickness of the positive electrode base material 4 in the above range, it is possible to increase the strength of the positive electrode base material 4 and the energy density per volume of the power storage element 10. The "average thickness" of the positive electrode base material 4 and the negative electrode base material 7 described later means a value obtained by dividing the mass of the base material having a predetermined area by the true density and area of the base material.

The intermediate layer is a layer arranged between the positive electrode base material 4 and the positive electrode active material layer 5. The intermediate layer contains conductive particles such as carbon particles to reduce the contact resistance between the positive electrode base material 4 and the positive electrode active material layer 5. The composition of the intermediate layer is not particularly limited, and includes, for example, a resin binder and conductive particles.

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

The positive electrode active material contained in the positive electrode active material layer 5 can be appropriately selected from known positive electrode active materials usually used for lithium ion secondary batteries and all-solid-state batteries. As the positive electrode active material, a material capable of occluding and releasing lithium ions is usually used. For example, a lithium transition metal composite oxide having an α-NaFeO type ₂ crystal structure, a lithium transition metal composite oxide having a spinel type crystal structure, a polyanion compound, a chalcogen compound, sulfur and the like can be mentioned. Examples of the lithium transition metal composite oxide having an α-NaFeO type ₂ crystal structure include Li [Li _x Ni _1-x ] O ₂ (0 ≦ x <0.5) and Li [Li _x Ni _γ Co _(1- ). _x-γ) ] O ₂ (0 ≦ x <0.5, 0 <γ <1), Li [Li _x Ni _γ Mn _β Co _(1-x-γ-β) ] O ₂ (0 ≦ x <0) .5, 0 <γ, 0 <β, 0.5 <γ + β <1) and the like. Examples of the lithium transition metal composite oxide having a spinel-type crystal structure include Li _x Mn ₂ O ₄ and Li _x Ni _γ Mn _(2-γ) O ₄ . Examples of the polyanionic compound include LiFePO ₄ , LiMnPO ₄ , LiNiPO ₄ , LiCoPO ₄ , Li ₃ V ₂ (PO ₄ ) ₃ , Li ₂ MnSiO ₄ , Li ₂ CoPO ₄ F and the like. Examples of the chalcogen compound include titanium disulfide, molybdenum disulfide, molybdenum dioxide and the like. The atoms or polyanions in these materials may be partially substituted with atoms or anion species consisting of other elements. The surface of the positive electrode active material may be coated with an oxide such as lithium niobate, lithium titanate, or lithium phosphate. In the positive electrode active material layer, one kind of these positive electrode active materials may be used alone, or two or more kinds may be mixed and used.

The average particle size of the positive electrode active material is preferably 0.1 μm or more and 20 μm or less, for example. By setting the average particle size of the positive electrode active material to the above lower limit or more, the production or handling of the positive electrode active material becomes easy. By setting the average particle size of the positive electrode active material to the above upper limit or less, the electron conductivity of the positive electrode active material layer 5 is improved. Here, the "average particle size" is based on JIS-Z-8825 (2013), and is based on the particle size distribution measured by the laser diffraction / scattering method for a diluted solution obtained by diluting the particles with a solvent. -It means a value in which the volume-based integrated distribution calculated in accordance with Z-8819-2 (2001) is 50%.

A crusher, a classifier, or the like is used to obtain particles in a predetermined shape. Examples of the crushing method include a method using a mortar, a ball mill, a sand mill, a vibrating ball mill, a planetary ball mill, a jet mill, a counter jet mill, a swirling airflow type jet mill, a sieve, or the like. At the time of pulverization, wet pulverization in which water or an organic solvent such as hexane coexists can also be used. As a classification method, a sieve, a wind power classifier, or the like is used as needed for both dry and wet types.

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

When the positive electrode active material layer 5 contains a solid electrolyte, the content of the solid electrolyte is preferably 10% by mass or more and 90% by mass or less, more preferably 20% by mass or more and 70% by mass or less, and further preferably 50% by mass or less. It may be preferable. By setting the content of the solid electrolyte in the above range, the electric capacity of the power storage element can be increased. When the solid electrolyte according to the embodiment of the present invention is used for the positive electrode active material layer 5, the content of the solid electrolyte according to the embodiment of the present invention in the positive electrode active material layer 5 is 50% by mass. The above is preferable, 70% by mass or more is more preferable, 90% by mass or more is further preferable, and substantially 100% by mass is further preferable.

The mixture of the positive electrode active material and the solid electrolyte is a mixture produced by mixing the positive electrode active material, the solid electrolyte and the like by a mechanical milling method or the like. For example, a mixture of a positive electrode active material and a solid electrolyte or the like can be obtained by mixing a particulate positive electrode active material, a particulate solid electrolyte or the like. The composite of the positive electrode active material and the solid electrolyte includes a composite having a chemical or physical bond between the positive electrode active material and the solid electrolyte, and a physically complex of the positive electrode active material and the solid electrolyte. Examples thereof include a complex and the like. In the above composite, a positive electrode active material, a solid electrolyte, and the like are present in one particle, and for example, a positive electrode active material, a solid electrolyte, and the like forming an aggregated state, and a surface of the positive electrode active material. Examples thereof include those having a film containing a solid electrolyte or the like formed at least in a part thereof.

The conductive agent is not particularly limited as long as it is a conductive material. Examples of such a conductive agent include carbonaceous materials, metals, conductive ceramics and the like. Examples of the carbonaceous material include graphitized carbon, non-graphitized carbon, graphene-based carbon and the like. Examples of the non-graphitized carbon include carbon nanofibers, pitch-based carbon fibers, and carbon black. Examples of carbon black include furnace black, acetylene black, and ketjen black. Examples of graphene-based carbons include graphene, carbon nanotubes (CNTs), fullerenes and the like. Examples of the shape of the conductive agent include powder and fibrous. As the conductive agent, one of these materials may be used alone, or two or more of them may be mixed and used. Further, these materials may be combined and used. For example, a material in which carbon black and CNT are combined may be used. Among these, carbon black is preferable from the viewpoint of electron conductivity and coatability, and acetylene black is particularly preferable.

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

Examples of the binder include fluororesins (polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), etc.), thermoplastic resins such as polyethylene, polypropylene, and polyimide; ethylene-propylene-diene rubber (EPDM), sulfonated EPDM, and the like. Elastomers such as styrene-butadiene rubber (SBR) and fluororubber; polysaccharide polymers and the like can be mentioned.

The content of the binder in the positive electrode active material layer 5 is preferably 1% by mass or more and 10% by mass, and more preferably 3% by mass or more and 9% by mass or less. By setting the content of the binder in the above range, the active substance can be stably retained.

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

The filler is not particularly limited. Fillers include polyolefins such as polypropylene and polyethylene, silicon dioxide, aluminum oxide, titanium dioxide, calcium oxide, strontium oxide, barium oxide, magnesium oxide, inorganic oxides such as aluminosilicate, magnesium hydroxide, calcium hydroxide, and water. Hydroxides such as aluminum oxide, carbonates such as calcium carbonate, sparingly soluble ion crystals such as calcium fluoride, barium fluoride, barium sulfate, nitrides such as aluminum nitride and silicon nitride, talc, montmorillonite, boehmite and zeolite. , Apatite, Kaolin, Murite, Spinel, Olivin, Sericite, Bentonite, Mica and other mineral resource-derived substances or man-made products thereof.

The positive electrode active material layer 5 is a typical non-metal element such as B, N, P, F, Cl, Br, I, Li, Na, Mg, Al, K, Ca, Zn, Ga, Ge, Sn, Sr, Ba. Typical metal elements such as Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, Nb, W and other transition metal elements are used as positive electrode active materials, conductive agents, binders, thickeners, etc. It may be contained as a component other than the filler.

The average thickness of the positive electrode active material layer 5 is preferably 30 μm or more and 1,000 μm or less, and more preferably 60 μm or more and 500 μm or less. By setting the average thickness of the positive electrode active material layer 5 to be equal to or greater than the above lower limit, a power storage element 10 having a high energy density can be obtained. By setting the average thickness of the positive electrode active material layer 5 to be equal to or less than the above upper limit, the power storage element 10 can be downsized. The average thickness of the positive electrode active material layer 5 is the average value of the thickness measured at any five locations. The same applies to the average thickness of the negative electrode active material layer 6 and the isolation layer 3, which will be described later.

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

(Negative electrode base material)
The negative electrode base material 7 has conductivity. As the material of the negative electrode base material 7, a metal such as copper, nickel, stainless steel, nickel-plated steel, aluminum, or an alloy thereof is used. Among these, copper or a copper alloy is preferable. Examples of the negative electrode base material include a foil and a vapor-deposited film, and the foil is preferable from the viewpoint of cost. Therefore, a copper foil or a copper alloy foil is preferable as the negative electrode base material. Examples of the copper foil include rolled copper foil, electrolytic copper foil and the like.

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

(Negative electrode active material layer)
The negative electrode active material layer 6 contains a negative electrode active material. The negative electrode active material layer 6 can be formed from a so-called negative electrode mixture containing a negative electrode active material. The negative electrode active material layer 6 may contain a mixture or a composite containing a negative electrode active material and a solid electrolyte. The negative electrode active material layer 6 contains optional components such as a conductive agent, a binder, a thickener, and a filler, if necessary. The types and suitable contents of the optional components in the negative electrode active material layer 6 are the same as those of the above-mentioned optional components in the positive electrode active material layer 5. One or more of each of these optional components may not be substantially contained in the negative electrode active material layer 6.

The negative electrode active material layer 6 is a typical non-metal element such as B, N, P, F, Cl, Br, I, Li, Na, Mg, Al, K, Ca, Zn, Ga, Ge, Sn, Sr, Ba. Typical metal elements such as Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, Ta, Hf, Nb, W and other transition metal elements are used as negative electrode active materials, conductive agents, binders, etc. It may be contained as a component other than a thickener and a filler.

The negative electrode active material can be appropriately selected from known negative electrode active materials usually used for lithium ion secondary batteries and all-solid-state batteries. As the negative electrode active material, a material capable of occluding and releasing lithium ions is usually used. Examples of the negative electrode active material include metal Li; metal or semi-metal such as Si and Sn; metal oxide or semi-metal oxide such as Si oxide, Ti oxide and Sn oxide; Li ₄ Ti ₅ O ₁₂ ; Titanium-containing oxides such as LiTIO _{2 and} TiNb _{2O 7} ; polyphosphate compounds; silicon carbide; carbon materials such as graphite (graphite) and non-graphitric carbon (easy graphitable carbon or non-graphitizable carbon) can be mentioned. Be done. Among these materials, graphite and non-graphitic carbon are preferable. In the negative electrode active material layer 6, one kind of these materials may be used alone, or two or more kinds thereof may be mixed and used.

“Graphite” refers to a carbon material having an average lattice spacing (d ₀₀₂ ) of (002) planes determined by X-ray diffraction before charging / discharging or in a discharged state of 0.33 nm or more and less than 0.34 nm. Examples of graphite include natural graphite and artificial graphite. Artificial graphite is preferable from the viewpoint that a material having stable physical properties can be obtained.

"Non-graphitic carbon" refers to a carbon material having an average lattice spacing (d ₀₀₂ ) of the (002) plane determined by X-ray diffraction before charging / discharging or in a discharged state of 0.34 nm or more and 0.42 nm or less. say. Examples of non-graphitizable carbon include non-graphitizable carbon and easily graphitizable carbon. Examples of the non-graphitic carbon include a resin-derived material, a petroleum pitch-derived material, an alcohol-derived material, and the like.

Here, the "discharged state" means a state in which the open circuit voltage is 0.7 V or more in a unipolar battery using a negative electrode containing a carbon material as a negative electrode active material as a working electrode and a metal Li as a counter electrode. Since the potential of the metal Li counter electrode in the open circuit state is substantially equal to the redox potential of Li, the open circuit voltage in the single pole battery is substantially equal to the potential of the negative electrode containing the carbon material with respect to the redox potential of Li. .. That is, the fact that the open circuit voltage in the single-pole battery is 0.7 V or more means that the carbon material, which is the negative electrode active material, sufficiently releases lithium ions that can be occluded and discharged by charging and discharging. ..

The “non-graphitizable carbon” refers to a carbon material having d ₀₀₂ of 0.36 nm or more and 0.42 nm or less.

The “graphitizable carbon” refers to a carbon material having d ₀₀₂ of 0.34 nm or more and less than 0.36 nm.

The negative electrode active material is usually particles (powder). The average particle size of the negative electrode active material can be, for example, 1 nm or more and 100 μm or less. When the negative electrode active material is, for example, a carbon material, the average particle size thereof may be preferably 1 μm or more and 100 μm or less. When the negative electrode active material is a metal, a semi-metal, a metal oxide, a semi-metal oxide, a titanium-containing oxide, a polyphosphate compound or the like, the average particle size thereof may be preferably 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 higher than the above lower limit, the production or handling of the negative electrode active material becomes easy. By setting the average particle size of the negative electrode active material to the above upper limit or less, the electron conductivity of the active material layer is improved. A crusher, a classifier, or the like is used to obtain a powder having a predetermined particle size. The pulverization method and the powder grade method can be selected from, for example, the methods exemplified in the positive electrode layer 1.

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

When the negative electrode active material layer 6 contains a solid electrolyte, the content of the solid electrolyte is preferably 10% by mass or more and 90% by mass or less, more preferably 20% by mass or more and 70% by mass or less, and further preferably 50% by mass or less. It may be preferable. By setting the content of the solid electrolyte in the above range, the electric capacity of the power storage element 10 can be increased. When the solid electrolyte according to the embodiment of the present invention is used for the negative electrode active material layer 6, the content of the solid electrolyte according to the embodiment of the present invention in the negative electrode active material layer 6 is 50% by mass. The above is preferable, 70% by mass or more is more preferable, 90% by mass or more is further preferable, and substantially 100% by mass is further preferable.

The mixture or composite of the negative electrode active material and the solid electrolyte may be the above-mentioned mixture or composite of the positive electrode active material and the solid electrolyte, in which the positive electrode active material is replaced with the negative electrode active material.

The average thickness of the negative electrode active material layer 6 is preferably 30 μm or more and 1,000 μm or less, and more preferably 60 μm or more and 500 μm or less. By setting the average thickness of the negative electrode active material layer 6 to be equal to or greater than the above lower limit, a power storage element 10 having a high energy density can be obtained. By setting the average thickness of the negative electrode active material layer 6 to be equal to or less than the above upper limit, the power storage element 10 can be downsized.

[Isolation layer]
The isolation layer 3 contains a solid electrolyte. As the solid electrolyte contained in the isolation layer 3, various solid electrolytes exemplified in the positive electrode active material layer 5 can be used in addition to the solid electrolyte according to the embodiment of the present invention described above, and among them, a sulfide solid. It is preferable to use an electrolyte. The content of the solid electrolyte in the isolation layer 3 is preferably 70% by mass or more, more preferably 90% by mass or more, further preferably 99% by mass or more, and even more preferably substantially 100% by mass. be. When the solid electrolyte according to the embodiment of the present invention is used for the isolation layer 3, the content of the solid electrolyte according to the embodiment of the present invention in the isolation layer 3 is 50% by mass or more. Is more preferable, 70% by mass or more is more preferable, 90% by mass or more is further preferable, and substantially 100% by mass is further preferable.

The isolation layer 3 may contain optional components such as a binder, a thickener, and a filler. Optional components such as a binder, a thickener, and a filler can be selected from the materials exemplified in the positive electrode active material layer 5.

The average thickness of the isolation layer 3 is preferably 1 μm or more and 50 μm or less, and more preferably 3 μm or more and 20 μm or less. By setting the average thickness of the isolation layer 3 to be equal to or greater than the above lower limit, it is possible to insulate the positive electrode layer 1 and the negative electrode layer 2 with high certainty. By setting the average thickness of the isolation layer 3 to be equal to or less than the above upper limit, it is possible to increase the energy density of the power storage element 10.

The power storage element of the present embodiment is a power source for automobiles such as an electric vehicle (EV), a hybrid vehicle (HEV), and a plug-in hybrid vehicle (PHEV), a power source for electronic devices such as a personal computer and a communication terminal, or a power source for power storage. For example, it can be mounted as a power storage unit (battery module) composed of a plurality of power storage elements assembled together. In this case, the technique according to the embodiment of the present invention may be applied to at least one power storage element included in the power storage unit.

FIG. 2 shows an example of a power storage device 30 in which a power storage unit 20 in which two or more electrically connected power storage elements 10 are assembled is further assembled. The power storage device 30 may include a bus bar (not shown) for electrically connecting two or more power storage elements 10, a bus bar (not shown) for electrically connecting two or more power storage units 20 and the like. The power storage unit 20 or the power storage device 30 may include a state monitoring device (not shown) for monitoring the state of one or more power storage elements.

<Manufacturing method of sulfide solid electrolyte>
The method for producing a sulfide solid electrolyte according to an embodiment of the present invention comprises heat-treating a sulfide glass containing lithium, sulfur, phosphorus and chlorine and having a valence of phosphorus pentavalent (heat treatment step). .. In the method for producing the sulfide solid electrolyte, a composition containing, for example, lithium, phosphorus, sulfur and chlorine is prepared as another step before the heat treatment (preparation step), and the composition is prepared. It is preferable to provide a sulfide glass containing lithium, sulfur, phosphorus and chlorine and having a valence of phosphorus pentavalent (sulfide glass production step).

(Preparation process)
In this step, a composition containing lithium, phosphorus, sulfur and chlorine is prepared. The composition is usually a mixture of two or more compounds containing at least one element of lithium, phosphorus, sulfur and chlorine. The composition (mixture) may contain each element of lithium, phosphorus, sulfur and chlorine. One compound may contain two or more elements of lithium, phosphorus, sulfur and chlorine. For example, Li ₂ S described later can be mentioned as a compound containing lithium and sulfur, P ₂ S ₅ described later can be mentioned as a compound containing phosphorus and sulfur, and Li Cl described later can be mentioned as a compound containing lithium and chlorine.

Examples of the lithium-containing compound and the like include Li _2S , metallic lithium and the like. In addition, LiCl or the like described later may be used. Among these, Li _2S is preferable. As the compound containing lithium, one kind may be used alone, or two or more kinds may be mixed and used.

Examples of the phosphorus _- containing compound and the like include P2 _S5 and the like. As the compound containing phosphorus, one kind may be used alone, or two or more kinds may be mixed and used.

Examples of the sulfur-containing compound include Li ₂ S, P ₂ S _{5, and} elemental sulfur. Among these, Li ₂ S and P ₂ S ₅ are preferable. As the compound containing sulfur, one kind may be used alone, or two or more kinds may be mixed and used.

Examples of the chlorine-containing compound include LiCl. As the compound containing chlorine, one kind may be used alone, or two or more kinds may be mixed and used.

For example, as one embodiment, the composition is preferably a mixture of Li ₂ S, P ₂ S ₅ and Li Cl.

The specific content and suitable content of each element (lithium, phosphorus, sulfur and chlorine) in the above composition are the respective elements (lithium, phosphorus, sulfur and chlorine) in the sulfide solid electrolyte according to the embodiment of the present invention described above. It is the same as the specific content and the preferable content of chlorine).

(Sulfide glass manufacturing process)
In this step, for example, a sulfide glass containing lithium, sulfur, phosphorus and chlorine and having a pentavalent phosphorus valence is produced by the following procedure. In this step, the composition containing lithium, phosphorus, sulfur and chlorine is treated with, for example, a mechanical milling method to react the composition to obtain sulfide glass. The sulfide glass includes the general formula (100-z) (yLi ₂ S · (1-y) P ₂ S ₅ ) · zLiCl · αM (provided that 0.74 ≦ y ≦ 0.78, 5 ≦ z ≦. 55, 0 ≦ α ≦ 30. M represents one or more elements other than Li, P, S, Cl), and thus has a sulfide having higher ionic conductivity. Solid electrolytes can be produced. The preferred ranges of y, z and α in the above general formula are as described above. Further, the means for obtaining the sulfide glass is not limited to this, and other methods may be used for obtaining the sulfide glass. For example, instead of the mechanical milling method, a melt quenching method or the like may be performed. "Sulfide glass" means a sulfide solid electrolyte containing an amorphous structure.

The treatment by the mechanical milling method may be either a dry method or a wet method, but is preferably a wet method because the raw material compound can be mixed more uniformly. Examples of the device for performing the processing by the mechanical milling method include a container-driven mill, a medium stirring mill, a high-speed rotary crusher, a roller mill, and a jet mill. Examples of the container-driven mill include a rotary mill, a vibration mill, a planetary ball mill, and the like. Examples of the medium stirring mill include an attritor and a bead mill. Examples of the high-speed rotary crusher include a hammer mill and a pin mill. Among these, a container-driven mill is preferable, and a planetary ball mill is particularly preferable.

(Heat treatment process)
In this step, sulfide glass containing lithium, sulfur, phosphorus and chlorine and having a valence of 5 phosphorus is heat-treated. As a result, the sulfide glass is crystallized, and the sulfide glass ceramics can be produced. The heat treatment may be performed in a reduced pressure atmosphere or in an inert gas atmosphere.

The temperature of the heat treatment is lower than the crystallization temperature of the sulfide glass. The lower limit of the difference between the crystallization temperature and the heat treatment temperature is 20 ° C, preferably 23 ° C, and more preferably 25 ° C. On the other hand, the upper limit of the difference between the crystallization temperature and the heat treatment temperature is 45 ° C, preferably 42 ° C, more preferably 40 ° C. The temperature of the heat treatment is lower than the crystallization temperature of the sulfide glass, and by setting the difference between the crystallization temperature and the heat treatment temperature within the above range, the crystal of β _- Li ₃ PS4 having low ionic conductivity A sulfide solid electrolyte having a crystalline phase with high ionic conductivity can be produced by suppressing the precipitation of the phase. Further, in the Li ₂ SP ₂ S ₅ -LiCl solid electrolyte, a crystal phase having high ionic conductivity can be precipitated in a relatively wide composition range, so that variation in characteristics due to composition unevenness during mass production can be suppressed. can.

The crystallization temperature can be determined by differential scanning calorimetry (DSC).

<Manufacturing method of power storage element>
The method for manufacturing a power storage element according to an embodiment of the present invention is a generally known method except that the solid electrolyte according to the embodiment of the present invention is used for producing at least one of a positive electrode layer, an isolation layer and a negative electrode layer. Can be done by. Specifically, the manufacturing method is, for example, (1) preparing a positive electrode mixture, (2) preparing a material for an isolation layer, (3) preparing a negative electrode mixture, and (4) preparing a positive electrode. The layer, the isolation layer and the negative electrode layer are laminated. Hereinafter, each process will be described in detail.

(1) Positive electrode mixture preparation step In this step, a positive electrode mixture for forming a positive electrode layer (positive electrode active material layer) is usually produced. The method for producing the positive electrode mixture is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include treatment of the material of the positive electrode mixture by a mechanical milling method, compression molding of the positive electrode active material, and sputtering using the target material of the positive electrode active material. When the positive electrode mixture contains a mixture or a composite containing a positive electrode active material and a solid electrolyte, this step mixes the positive electrode active material and the solid electrolyte by using, for example, a mechanical milling method, and obtains the positive electrode active material. It can include making a mixture or complex with a solid electrolyte.

(2) Material preparation process for isolation layer In this step, a material for forming the isolation layer is usually produced. When the power storage element is a lithium ion power storage element, the material for the isolation layer is usually a solid electrolyte. The solid electrolyte as the material for the isolation layer can be produced by a conventionally known method. For example, it can be obtained by treating a predetermined material by a mechanical milling method. A material for an isolation layer may be produced by heating a predetermined material to a melting temperature or higher by a melting quenching method, melting and mixing the two at a predetermined ratio, and quenching. Other methods for synthesizing the material for the isolation layer include, for example, a solid phase method in which the material is sealed under reduced pressure and calcined, a liquid phase method such as dissolution precipitation, a gas phase method (PLD), and calcining in an argon atmosphere after mechanical milling. Can be mentioned. When the material for the isolation layer is the sulfide solid electrolyte, the method for producing the sulfide solid electrolyte is used for producing the material for the isolation layer.

(3) Negative electrode mixture preparation step In this step, a negative electrode mixture for forming a negative electrode layer (negative electrode active material layer) is usually produced. The specific method for producing the negative electrode mixture is the same as that for the positive electrode mixture. When the negative electrode mixture contains a mixture or a composite containing a negative electrode active material and a solid electrolyte, in this step, the negative electrode active material and the solid electrolyte are mixed by using, for example, a mechanical milling method, and the negative electrode active material is combined with the negative electrode active material. It can include making a mixture or complex with a solid electrolyte.

(Laminating process)
In this step, for example, a positive electrode layer having a positive electrode base material and a positive electrode active material layer, an isolation layer, and a negative electrode layer having a negative electrode base material and a negative electrode active material layer are laminated. In this step, the positive electrode layer, the isolation layer, and the negative electrode layer may be sequentially formed in this order, or vice versa, and the order of formation of each layer is not particularly limited. The positive electrode layer is formed by, for example, pressure molding a positive electrode base material and a positive electrode mixture, the isolation layer is formed by pressure molding a material for an isolation layer, and the negative electrode layer is a negative electrode base material. And the negative electrode mixture is formed by pressure molding. The positive electrode layer, the isolation layer, and the negative electrode layer may be laminated by pressure molding the positive electrode base material, the positive electrode mixture, the isolation layer material, the negative electrode mixture, and the negative electrode base material at once. The positive electrode layer and the negative electrode layer may be formed in advance, and the isolation layer may be pressure-molded and laminated.

[Other embodiments]
The present invention is not limited to the above embodiment, and can be implemented in various modifications and improvements in addition to the above embodiment. For example, the power storage element according to the present invention may include a layer other than the positive electrode layer, the isolation layer, and the negative electrode layer. Further, the power storage element according to the present invention may contain a liquid in one or more of the layers. The power storage element according to the present invention may be a capacitor or the like in addition to the power storage element which is a secondary battery.

The configuration of the all-solid-state battery according to the present invention is not particularly limited, and may include other layers other than the negative electrode layer, the positive electrode layer, and the isolation layer, such as an intermediate layer and an adhesive layer.

<Example>
Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples.

[Examples 1 to 7 and Comparative Examples 1 to 5]
The sulfide solid electrolytes of Examples 1 to 7 and Comparative Examples 1 to 5 were synthesized by the following treatments.
(Preparation process)
Li ₂ S (purity 99.98%, manufactured by Aldrich), P ₂ S ₅ (purity 99%, manufactured by Aldrich) and LiCl (purity 99.998%, manufactured by Aldrich) in a glove box with a dew point of -50 ° C or lower in an argon atmosphere. ) Was mixed in a mortar to prepare a composition containing Li, P, S, and Cl.
(Sulfide glass manufacturing process)
1.0 g of the above composition was put into a closed 80 mL zirconia pot containing 900 zirconia balls having a diameter of 4 mm. A planetary ball mill (manufactured by FRITSCH, model number Premium line P-7) was used to perform treatment by a mechanical milling method at a revolution speed of 510 rpm in a range of 10 to 25 hours to obtain sulfide glass.
(Heat treatment process)
The sulfide glass is heated from room temperature to the temperature shown in Table 1 at a heating rate of 2 ° C./min, and then heat-treated at the temperature shown in Table 1 for 2 hours from Example 1 to Example 7 and Comparative Example 1. The sulfide solid electrolyte of Comparative Example 5 was synthesized.

[Comparative Example 6]
In the preparatory step, Li ₂ S (purity 99.98%, manufactured by Aldrich) and P ₂ S ₅ (purity 99%, manufactured by Aldrich) are mixed in a mortar in a glove box having an argon atmosphere with a dew point of -50 ° C or lower, and Li, The same treatment as in Example 1 above was performed except that the composition containing P and S was prepared.

[Reference Example 1]
Li ₂ S (purity 99.98%, manufactured by Aldrich), P ₂ S ₅ (purity 99%, manufactured by Aldrich) and LiBr (purity 99.999%) in a glove box with an argon atmosphere with a dew point of -50 ° C or less in the preparatory step. , Aldrich) was mixed in a mortar, and the same treatment as in Example 1 above was carried out except that a composition containing Li, P, S and Br was prepared.

[Reference Example 2]
Li _{2S (purity 99.98%, manufactured by Aldrich), P2 S 5 ( purity} 99%, manufactured by Aldrich) and LiI (purity 99.999%) in a glove box with an argon atmosphere with a dew point of -50 ° C or less in the preparation step. , Aldrich) was mixed in a mortar, and the same treatment as in Example 1 above was carried out except that a composition containing Li, P, S and I was prepared.

The crystallization temperature _TC was determined by measuring with DSC by the following method. Using a DSC device (Thermo Plus DSC8230 manufactured by Rigaku Co., Ltd.) and a steel closed pan, the temperature was raised from room temperature to 400 ° C. at 10 ° C./min.

[evaluation]
(1) XRD analysis X-ray diffraction measurement was performed by the above method.

3 to 5 show X-ray diffraction patterns in the range of 2θ = 10 ° to 40 ° of Examples and Comparative Examples. Table 1 shows the crystal structure identified from the X-ray diffraction pattern.

(2) Ion conductivity (σ)
The ionic conductivity (σ ₂₅ ) of the solid electrolytes of each Example and Comparative Example at 25 ° C. was determined by measuring the AC impedance by the above method using "VMP-300" manufactured by Bio-Logic. Table 1 shows the ionic conductivity of Examples and Comparative Examples at 25 ° C.

As shown in FIGS. 3 to 5, peaks were observed in the sulfide solid electrolytes of Examples 1 to 7, Comparative Examples 2 to 6, Reference Example 1 and Reference Example 2 in the X-ray diffraction measurement. It was confirmed to have a crystal structure. By setting the difference between the crystallization temperature and the heat treatment temperature to 20 ° C. or higher and 45 ° C. or lower in the heat treatment step, 2θ = 17.8 ° ± 0.5 °, 19.1 ° ± in the X-ray diffraction measurement. Implementations with a crystal structure (crystal phase A) having diffraction peaks at 0.5 °, 21.7 ° ± 0.5 °, 23.8 ° ± 0.5 °, and 30.85 ° ± 0.5 °. The sulfide solid electrolyte of Example 1 to Example 7 could be obtained. On the other hand, the sulfide solid electrolytes of Comparative Examples 1 to 5 obtained by setting the difference between the crystallization temperature and the heat treatment temperature to less than 20 ° C or more than 45 ° C have β-Li having low ionic conductivity. ₃ It had a crystalline phase of _PS4 or had an amorphous phase. Further, as shown in Table 1 and FIG. 5, Comparative Example 6 of the composition, which does not contain chlorine and is represented by 75Li ₂ S. 25P ₂ S ₅ , is a crystal phase of β-Li ₃ PS ₄ having low ion conductivity. Had.

As shown in Table 1, the sulfide solid electrolytes of Examples 1 to 7 had good ionic conductivity at 25 ° C. On the other hand, it can be seen that the sulfide solid electrolytes of Comparative Examples 1 to 6 have lower ionic conductivity than those of Examples 1 to 7. In general, the good range of ionic conductivity of the sulfide solid electrolyte differs depending on the composition constituting the sulfide solid electrolyte. A good range of ionic conductivity of a sulfide solid electrolyte containing a composition represented by the general formula (100-z) (yLi ₂ S · (1-y) P ₂ S ₅ ) · zLiCl is, for example, z = 15. In the case of 7.0 × 10 ^-4 S / cm or more and 3.0 × 10 ^-3 S / cm or less, and in the case of z = 30, 6.0 × 10 ^-4 S / cm or more and 2.0. It is considered that it is × 10 ^-3 S / cm or less, and when z = 50, it is 4.0 × 10 ^-4 S / cm or more and 1.0 × 10 ^-3 S / cm or less.

Further, it is represented by Reference Example 1 and 85 (0.75Li ₂ S / 0.25P ₂ S ₅ ) / 15LiI of the composition represented by 85 (0.75Li ₂ S / 0.25P ₂ S ₅ ) / 15LiBr. Reference Example 2 of the composition had a crystal structure containing a crystal phase different from the crystal phase A of the sulfide solid electrolyte (referred to as crystal phase B in Table 1). That is, in Comparative Example 6, Reference Example 1 and Reference Example 2, the crystal phase of the sulfide solid electrolyte is present even though the difference between the crystallization temperature and the heat treatment temperature is 20 ° C. or higher and 45 ° C. or lower. It has a crystal phase different from that of A, and it can be seen that the crystal phase A is a peculiar crystal phase possessed by the sulfide solid electrolyte containing chlorine.

From the above results, it was shown that the sulfide solid electrolyte according to the present invention has excellent ionic conductivity.

The solid electrolyte according to the present invention is suitably used as a solid electrolyte for a power storage element such as an all-solid-state battery.

1 Positive electrode layer 2 Negative electrode layer 3 Isolation layer 4 Positive electrode base material 5 Positive electrode active material layer 6 Negative electrode active material layer 7 Negative electrode base material 10 Power storage element (all-solid-state battery)
20 Power storage unit 30 Power storage device

Claims (6)

Contains lithium, sulfur, phosphorus and chlorine,
2θ = 17.8 ° ± 0.5 °, 19.1 ° ± 0.5 °, 21.7 ° ± 0.5 °, 23.8 ° ± 0.5 ° in X-ray diffraction measurement using CuKα ray , And a crystal structure with diffraction peaks at 30.85 ° ± 0.5 °.
The valence of phosphorus is 5 and
A sulfide solid electrolyte that is substantially free of the crystalline phase of β-Li ₃ PS ₄ . General formula (100-z) (yLi ₂ S · (1-y) P ₂ S ₅ ) · zLiCl · αM (where 0.74 ≦ y ≦ 0.78, 5 ≦ z ≦ 55, 0 ≦ α ≦ 30 The sulfide solid electrolyte according to claim 1, wherein M represents one or more elements other than Li, P, S, and Cl). The sulfide solid electrolyte according to claim 1 or 2, wherein the ionic conductivity at 25 ° C. is 6.0 × 10 ^-4 S / cm or more. A power storage device containing the sulfide solid electrolyte according to claim 1, claim 2 or claim 3. It comprises heat-treating a sulfide glass containing lithium, sulfur, phosphorus and chlorine and having a valence of 5 phosphorus.
The temperature of the heat treatment is lower than the crystallization temperature of the sulfide glass,
A method for producing a sulfide solid electrolyte in which the difference between the crystallization temperature and the heat treatment temperature is 20 ° C. or higher and 45 ° C. or lower. The sulfide glass has a general formula (yLi ₂ S · (1-y) P ₂ S ₅ ) · zLiCl · αM (provided that 0.74 ≦ y ≦ 0.78, 5 ≦ z ≦ 55, 0 ≦ α ≦ 30. M represents one or more elements other than Li, P, S, Cl).) The method for producing a sulfide solid electrolyte according to claim 5, which has a composition represented by). ..

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