JP2020119783A - Solid electrolyte, lithium ion power storage element, and manufacturing methods thereof - Google Patents

Abstract

To provide a solid electrolyte which enables the increase in discharge capacity of a lithium ion power storage element, a lithium ion power storage element having a large discharge capacity, and their manufacturing methods.SOLUTION: A solid electrolyte comprises lithium, phosphorus, sulfur and halogen. According to X-ray diffraction measurement by use of Cu Kα rays, the solid electrolyte has a diffraction pattern which can be assigned to a space group F-43m; the ratio (FWHM(311)/FWHM(222)) of a half value width(FWHM(311)) of a diffraction line representing (311) plane and a half value width(FWHM(222)) of a diffraction line representing (222) plane is 0.93 or more and 0.98 or less.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a solid electrolyte, a lithium-ion power storage element, and a method for manufacturing these.

Non-aqueous electrolyte secondary batteries represented by lithium ion secondary batteries are widely used in electronic devices such as personal computers and communication terminals, automobiles and the like because of their high energy density. The non-aqueous electrolyte secondary battery generally has a pair of electrodes electrically isolated by a separator, and a non-aqueous electrolyte interposed between the electrodes, and a charge such as lithium ion between the electrodes. Is configured to be charged and discharged. In addition, capacitors such as lithium ion capacitors and electric double layer capacitors have been widely spread as non-aqueous electrolyte storage elements other than non-aqueous electrolyte secondary batteries.

In recent years, as a non-aqueous electrolyte, a storage element using a solid electrolyte such as a sulfide-based solid electrolyte in place of the non-aqueous electrolyte solution in which an electrolyte salt is dissolved in a liquid such as an organic solvent has been proposed. As one of sulfide-based solid electrolytes, Argyrodite type solid electrolytes containing lithium, phosphorus, sulfur and halogen are known (see Patent Documents 1 and 2 and Non-Patent Documents 1 and 2). This solid electrolyte is said to have a crystal structure belonging to the space group F-43m. Conventionally, such a solid electrolyte has been synthesized by pulverizing and mixing solid raw materials by mechanical milling treatment using a ball mill or the like, and firing the resulting mixed powder.

JP, 2018-67552, A JP, 2017-117753, A

Prasada Rao Rayavarapu et al., "Variation in structure and Li+-ion migration in argyrodite-type Li6PS5X (X=Cl,Br,I) solid electolytesl8eS10e12eS18,Solid telyte", 18Solid. Sylvain Boulineau other, "Mechanochemical synthesis of Li-argyrodite Li6PS5X (X = Cl, Br, I) as sulfur-based solid electrolytes for all solid state batteries application", Solid State Ionics 221 (2012) 1-5

The storage element is required to have a large discharge capacity and the like. Even in the storage element using the conventional Argyrodite type solid electrolyte as described above, the discharge capacity cannot be said to be sufficient, and further improvement in charge/discharge performance is desired.

The present invention has been made based on the above circumstances, and an object thereof is a solid electrolyte capable of increasing the discharge capacity of a lithium-ion storage element, a lithium-ion storage element having a large discharge capacity, and these. It is to provide a manufacturing method.

One embodiment of the present invention made to solve the above problems is a diffraction pattern containing lithium, phosphorus, sulfur, and halogen, which can be assigned to the space group F-43m in an X-ray diffraction measurement using CuKα ray. Of the diffraction line showing the (311) plane (FWHM(311)) and the half width of the diffraction line showing the (222) plane (FWHM(222)) (FWHM(311)/FWHM( 222)) is 0.93 or more and 0.98 or less.

Another aspect of the present invention is to prepare an organic liquid containing ether, a lithium source, a sulfur source and a halogen source, to prepare a raw material liquid, volatilize the organic liquid to obtain a solid body, And firing the precursor containing the solid body in this order, the content ratio of the ether in the organic liquid is 40% by volume or more, the precursor contains a phosphorus source, a method for producing a solid electrolyte, is there.

Another embodiment of the present invention is a lithium ion storage element, which comprises a positive electrode layer, an isolation layer, and a negative electrode layer, and the positive electrode layer, the isolation layer, the negative electrode layer, or a combination thereof includes the solid electrolyte. is there.

Another embodiment of the present invention comprises producing at least one of a positive electrode layer, a separation layer and a negative electrode layer using the solid electrolyte or the solid electrolyte obtained by the method for producing the solid electrolyte, lithium ion It is a manufacturing method of a storage element.

According to the present invention, it is possible to provide a solid electrolyte capable of increasing the discharge capacity of a lithium-ion power storage element, a lithium-ion power storage element having a large discharge capacity, and a method for manufacturing these.

FIG. 1 is a schematic cross-sectional view of an all-solid-state battery that is an embodiment of the lithium-ion storage device of the present invention.

The solid electrolyte according to one embodiment of the present invention contains lithium, phosphorus, sulfur, and halogen, and has a diffraction pattern that can be assigned to the space group F-43m in an X-ray diffraction measurement using CuKα ray, The ratio (FWHM(311)/FWHM(222)) of the full width at half maximum of the diffraction line showing the (311) plane (FWHM(311)) and the full width at half maximum of the diffraction line showing the (222) plane (FWHM(222)) is The solid electrolyte is 0.93 or more and 0.98 or less.

The solid electrolyte can increase the discharge capacity of the lithium ion storage element. The reason why such an effect occurs is not clear, but the following reason is presumed. The above-mentioned half width ratio (FWHM(311)/FWHM(222)) is an index depending on the crystal orientation. That is, when the ratio of the full width at half maximum is in the above range, the crystal orientation is considered to be in an appropriate state for enhancing the charge/discharge performance, and it is presumed that the discharge capacity is increased.

It should be noted that "-4" in the space group "F-43m" represents the target element of the four-fold anti-axis, and should be originally described by adding a bar "-" over "4". The X-ray diffraction measurement using the CuKα ray is performed by the following procedure. An airtight sample holder for X-ray diffraction measurement is filled with a solid electrolyte powder to be used for measurement under an argon atmosphere having a dew point of -50°C or lower. The powder X-ray diffraction measurement is performed using an X-ray diffractometer (“MiniFlex II” manufactured by Rigaku). The radiation source is CuKα rays, the tube voltage is 30 kV, the tube current is 15 mA, and the diffracted X-rays are 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 divergence slit width is 0.625°, the light receiving slit width is 13 mm (OPEN), and the scattering slit width is 8 mm. In addition, the obtained X-ray diffraction pattern is automatically analyzed using PDXL (analysis software, manufactured by Rigaku). Here, "Refine background" and "Automatic" are selected in the work window of the PDXL software, and refining is performed so that the intensity error between the actually measured pattern and the calculated pattern is 4000 or less. Background processing is performed by this refinement, and the value of the peak intensity of each diffraction line and the value of the half width are obtained based on the result of subtracting the baseline.

The full width at half maximum (FWHM(311)) is preferably 0.130° or more. When the full width at half maximum (FWHM(311)) is 0.130° or more in the solid electrolyte according to the embodiment of the present invention, the crystal orientation is in a better state, and thus the discharge capacity is increased. can do.

A method for producing a solid electrolyte according to an embodiment of the present invention, an organic liquid containing ether, a lithium source, a sulfur source and a halogen source, to prepare a raw material liquid containing, by volatilizing the organic liquid, Providing a solid body and firing the precursor containing the solid body in this order, the content ratio of the ether in the organic liquid is 40 vol% or more, the precursor contains a phosphorus source, It is a manufacturing method of a solid electrolyte.

According to the method for producing a solid electrolyte, it is possible to obtain a solid electrolyte capable of increasing the discharge capacity of a lithium ion storage element. The reason for this is not clear, but the following is presumed. When the organic liquid is volatilized in the raw material liquid containing the organic liquid, it is presumed that a solid body in which lithium, sulfur, and halogen are in an appropriate orientation state is obtained. Therefore, it is presumed that by firing the precursor containing such a solid body, the crystal orientation of the obtained solid electrolyte is controlled to a good state.

A lithium ion power storage device according to an embodiment of the present invention includes a positive electrode layer, a separation layer, and a negative electrode layer, and the positive electrode layer, the separation layer, the negative electrode layer, or a combination thereof is an embodiment of the present invention. And a lithium ion storage element including the solid electrolyte according to claim 1. The lithium-ion storage element has a large discharge capacity.

A method for manufacturing a lithium-ion storage element according to an embodiment of the present invention uses at least one of a positive electrode layer, an isolation layer and a negative electrode layer, using the solid electrolyte or the solid electrolyte obtained by the method for manufacturing the solid electrolyte. A method for manufacturing a lithium-ion power storage element, the method including manufacturing. According to the method for manufacturing a lithium ion power storage element, a lithium ion power storage element having a large discharge capacity can be obtained.

Hereinafter, a solid electrolyte according to an embodiment of the present invention, a method for manufacturing the same, a lithium-ion storage element, and a method for manufacturing the same will be described in detail.

<Solid electrolyte>
The solid electrolyte according to one embodiment of the present invention contains lithium, phosphorus, sulfur, and halogen. Examples of the halogen include chlorine, bromine and iodine, and chlorine is preferable.

The content ratio of each constituent element in the solid electrolyte is not particularly limited as long as it has a predetermined crystal structure. The lower limit of the content ratio of lithium to phosphorus in the solid electrolyte is preferably 5, and more preferably 5.5, still more preferably 5.9, still more preferably 6 in terms of molar ratio. The upper limit of the lithium content ratio is preferably 7, more preferably 6.5, and further preferably 6. As a lower limit of the content ratio of sulfur to phosphorus, the molar ratio is preferably 4, more preferably 4.5, still more preferably 4.9, still more preferably 5. The upper limit of the content ratio of sulfur is preferably 6, more preferably 5.5, further preferably 5.1, still more preferably 5. The lower limit of the content ratio of halogen to phosphorus is preferably 0.2, more preferably 0.5, still more preferably 1 in terms of molar ratio. The upper limit of the halogen content is preferably 1.8, more preferably 1.5, and even more preferably 1.

The solid electrolyte may further contain an element other than lithium, phosphorus, sulfur and halogen. Examples of other elements include magnesium and indium. The content ratio of the other element to phosphorus in the solid electrolyte is preferably 0.01 or more and 0.1 or less in terms of molar ratio. The solid electrolyte may not substantially contain any element other than lithium, phosphorus, sulfur, and halogen.

The solid electrolyte is preferably represented by the following formula (1).
_{Li 7-mx-y A x} PS 6-y Ha y ··· (1)
In the formula (1), A is magnesium or indium (hereinafter, magnesium or indium is also referred to as “element A”). Ha is halogen. x is a number of 0 or more and 0.1 or less. y is a number of 0.2 or more and 1.8 or less. m is the valence of the element A.

The above x may be preferably 0. The lower limit of y is preferably 0.5, and the upper limit is preferably 1.5. The above y is more preferably 1. The m may be 2 when the element A is magnesium and 3 when the element A is indium.

The solid electrolyte has a diffraction pattern that can be assigned to the space group F-43m in the X-ray diffraction measurement using CuKα ray. The solid electrolyte may have a crystal structure belonging to the space group F-43m. The solid electrolyte is a cubic crystal and has an Argyrodite type crystal structure.

In the above diffraction pattern of the solid electrolyte, the ratio (FWHM) of the full width at half maximum of the diffraction line showing the (311) plane (FWHM(311)) and the full width at half maximum of the diffraction line showing the (222) plane (FWHM(222)) The lower limit of (311)/FWHM(222)) is 0.93, preferably 0.94, more preferably 0.95, and even more preferably 0.96. On the other hand, the upper limit of this ratio (FWHM(311)/FWHM(222)) is 0.98, preferably 0.980, and more preferably 0.975. When the ratio (FWHM(311)/FWHM(222)) is within the above range, the crystal orientation is optimized, and the discharge capacity of the lithium ion storage element can be increased.

In the solid electrolyte, the diffraction line showing the (311) plane usually appears at a position of 2θ=29.5±0.5°. The diffraction line showing the (222) plane usually appears at a position of 2θ=31.0±0.5°.

As a lower limit of the half width (FWHM(311)), 0.130° is preferable. On the other hand, as the upper limit of the full width at half maximum (FWHM(311)), 0.20° is preferable, 0.18° is more preferable, 0.16° is further preferable, 0.15° is further preferable, and 0. 14° is particularly preferred. When the full width at half maximum (FWHM(311)) is within the above range, the crystal orientation is further optimized, and the discharge capacity of the lithium ion storage element can be further increased.

As a lower limit of the ionic conductivity of the solid electrolyte at 25° C., 1×10 ⁻⁴ S/cm is preferable, 2×10 ⁻⁴ S/cm is more preferable, and 1×10 ⁻³ S/cm is further preferable. When the ionic conductivity of the solid electrolyte at 25° C. is at least the above lower limit, the discharge capacity of the lithium ion storage element can be further increased. The upper limit of the ionic conductivity is, for example, 5×10 ⁻³ S/cm.

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

The shape of the solid electrolyte is not particularly limited and is usually granular, lumpy or the like. When the solid electrolyte is granular, the lower limit of the average particle size is, for example, 3 μm, preferably 5 μm, more preferably 10 μm. On the other hand, the upper limit is, for example, 100 μm, preferably 50 μm, more preferably 20 μm. When the average particle size of the solid electrolyte is within the above range, good ion conductivity is exhibited when used in a lithium ion storage element, and thus the discharge capacity can be further increased. The “average particle size” is based on JIS-Z-8825 (2013), and is based on the particle size distribution measured by a laser diffraction/scattering method with respect to a diluted solution prepared by diluting particles with a solvent. It means a value (median diameter) at which the volume-based cumulative distribution calculated according to −8819-2 (2001) is 50%. Hereinafter, the same applies to the average particle size. The average particle diameter of the solid electrolyte is specifically a value measured by the following method. The measurement is performed using a laser diffraction/scattering type particle size distribution measuring device (“Partica LA-960” manufactured by HORIBA) as a measuring device. Ultra-dehydrated heptane is used as the dispersion medium, and the measurement cell is filled with the dispersion liquid in which the particles of the sample to be measured are dispersed in the dispersion medium. The measurement cell is irradiated with laser light to obtain a scattered light distribution from the measurement sample. The particle size corresponding to the cumulative degree of 50% (D50) obtained from the scattered light distribution is defined as the average particle size.

The solid electrolyte can be preferably used as an electrolyte of a lithium-ion power storage device such as a lithium-ion secondary battery. Among them, it can be particularly preferably used as an electrolyte of 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 lithium ion power storage device.

<Method for producing solid electrolyte>
The method for producing the solid electrolyte is not particularly limited, but it can be suitably produced by the following method using a liquid phase method. That is, the method for producing a solid electrolyte according to an embodiment of the present invention,
(1) Preparing a raw material liquid containing an organic liquid containing ether and a lithium source, a sulfur source and a halogen source,
(2) Evaporating the organic liquid to obtain a solid body, and (3) firing the obtained precursor containing the solid body in this order. The content ratio of the ether in the organic liquid is 40% by volume or more. In addition, the precursor includes a phosphorus source. It is preferable that all the steps of the manufacturing method are performed under an inert atmosphere such as an argon atmosphere. Hereinafter, each step will be described in detail.

(1) Raw Material Liquid Preparation Step In this step, a raw material liquid containing an organic liquid and a lithium source, a sulfur source and a halogen source is prepared. The lithium source is a lithium atom and is not limited to existing as a simple substance. That is, it suffices that lithium atoms are present in the raw material liquid. Further, the lithium source may be present as a lithium ion or a polyatomic ion containing lithium in the raw material solution in a completely dissolved state, or a part thereof may be present without being dissolved. The same applies to phosphorus sources, sulfur sources and halogen sources other than lithium sources. However, it is preferable that at least a part of each of the lithium source, the sulfur source, and the halogen source is dissolved and present in the organic liquid.

The organic liquid contains ether. Examples of the ether include chain ethers such as dimethyl ether, methyl ethyl ether and diethyl ether, and cyclic ethers such as tetrahydrofuran, furan, tetrahydropyran and pyran. Of these, cyclic ethers are preferred, tetrahydrofuran and tetrahydropyran are more preferred, and tetrahydrofuran is even more preferred.

The lower limit of the content ratio of the ether in the organic liquid is 40% by volume, preferably 60% by volume, and more preferably 80% by volume. The ether content may be substantially 100% by volume. In the manufacturing method, by using the organic liquid having a high ether ratio in this manner, the solid electrolyte according to the embodiment of the present invention having good crystal orientation can be effectively obtained.

Examples of the organic liquid other than ether that may be contained in the organic liquid include alcohols, esters, ketones, amides, and the like, and alcohols are preferable. Examples of the alcohol include methanol, ethanol, propanol and the like, and ethanol is preferable.

It is preferable that the organic liquid does not contain water as much as possible. The water content in the organic liquid is preferably 0.01% by mass or less, more preferably 0.001% by mass or less.

In the raw material liquid preparation step, the raw material liquid can be prepared by adding a compound or a simple substance containing a lithium source, a sulfur source and a halogen source to the organic liquid and mixing them by stirring or the like. It is sufficient that the compound to be added and the simple substance as a whole contain a lithium atom, a sulfur atom and a halogen atom. As the compound, a compound composed of two or more kinds of atoms constituting the target solid electrolyte can be used. For example, Li ₂ S is mentioned as a compound composed of a lithium atom and a sulfur atom, and LiCl, LiBr and the like are mentioned as a compound containing a lithium atom and a halogen atom. The use ratio of these compounds is appropriately set according to the intended composition of the solid electrolyte.

The raw material liquid may further contain a phosphorus source. The phosphorus source may be present in the raw material liquid in a dissolved state, or may be present in an undissolved state. In some cases, it is preferable that at least a part of the phosphorus source exists in the raw material liquid without being dissolved. Examples of the compound containing a phosphorus atom include P ₂ S _{5 and the} like.

The raw material liquid may further contain other components depending on the composition of the solid electrolyte to be synthesized. For example, when the solid electrolyte to be synthesized contains magnesium, the raw material liquid further contains a magnesium source, and when the solid electrolyte to be synthesized contains indium, the raw material liquid further contains an indium source. Examples of the compound containing a magnesium atom include MgCl _{2 and the} like, and examples of the compound containing an indium atom include InCl _{3 and the} like. As the components other than the organic liquid, it is preferable that the raw material liquid does not substantially contain an element other than the element constituting the solid electrolyte to be synthesized.

(2) Volatilization Step In this step, the organic liquid in the raw material liquid is volatilized. By this volatilization, a solid body containing a lithium source, a sulfur source and a halogen source is obtained. In this solid body, lithium, sulfur and halogen are presumed to be a complex or the like having an appropriate orientation state, which is different from that obtained by, for example, the mechanical milling method.

The method for volatilizing the organic liquid is not particularly limited, and it can be performed by a known method such as natural drying, heat drying, and vacuum drying. The heating temperature for heat drying may be, for example, 50° C. or higher and 150° C. or lower. In addition, the vacuum drying may be performed while heating at the above heating temperature, for example.

(3) Firing step In this step, the precursor is fired. This precursor contains the solid body obtained in the above (2) volatilization step and also contains a phosphorus source. When the raw material liquid contains a phosphorus source in addition to the lithium source, the sulfur source and the halogen source, the obtained solid body contains the lithium source, the sulfur source, the halogen source and the phosphorus source. Therefore, this solid body can be directly subjected to firing as a precursor. You may add another component to the obtained solid body and use it as a precursor. The content ratios of the lithium source, the sulfur source, the halogen source, the phosphorus source, and the like used for the calcination are adjusted so that the composition of the target solid electrolyte is obtained.

The firing temperature in the above firing may be, for example, 500° C. or higher and 600° C. or lower. The firing time can be, for example, 3 hours or more and 24 hours or less.

<Lithium-ion storage element>
As an embodiment of the lithium-ion storage element of the present invention, an all-solid-state battery will be described below as a specific example. The all-solid-state battery 10 in FIG. 1 is a secondary battery in which a positive electrode layer 1 and a negative electrode layer 2 are arranged with an isolation layer 3 interposed therebetween. The positive electrode layer 1 has a positive electrode 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 all-solid-state battery 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 all-solid-state battery 10 contains a 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 one embodiment of the present invention. Since the all-solid-state battery 10 contains the solid electrolyte, the discharge capacity is large. The solid electrolyte is preferably contained in the positive electrode layer 1.

The all-solid-state battery 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-based solid electrolytes other than the solid electrolyte, oxide-based solid electrolytes, dry polymer electrolytes, gel polymer electrolytes, pseudo-solid electrolytes, and the like, and sulfide-based solid electrolytes are preferable. In addition, a plurality of different types of solid electrolytes may be contained in one layer of the all-solid-state battery 10, or different solid electrolytes may be contained in each layer.

The sulfide-based solid electrolyte, for example, _{Li 2 S-P 2 S 5} , Li 2 S-P 2 S 5 -LiI, Li 2 S-P 2 S 5 -LiCl, Li 2 S-P 2 S 5 -LiBr _{, Li 2 S-P 2 S} 5 -Li 2 O, Li 2 S-P 2 S 5 -Li 2 O-LiI, Li 2 S-P 2 S 5 -Li 3 N, Li 2 S-SiS 2, Li _{2 S-SiS 2 -LiI, Li} 2 S-SiS 2 -LiBr, Li 2 S-SiS 2 -LiCl, Li 2 S-SiS 2 -B 2 S 3 -LiI, Li 2 S-SiS 2 -P 2 S _{5 -LiI, Li 2 S-B} 2 S 3, Li 2 S-P 2 S 5 -Z m S 2n ( except, m, n is a positive number, Z is is either 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 ( provided that, x, y are positive numbers, M is, P, Si , Ge, B, Al, Ga, In)), and Li ₁₀ GeP ₂ S _{12 and the} like.

[Positive 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 can be, for example, a layer containing conductive particles and a resin binder.

(Positive electrode substrate)
The positive electrode base material 4 has conductivity. Having “conductivity” means that the volume resistivity measured according to JIS-H-0505 (1975) is 10 ⁷ Ω·cm or less, and “non-conductivity” means It means that the volume resistivity is more than 10 ⁷ Ω·cm. As a material of the positive electrode base material 4, a metal such as aluminum, titanium, tantalum, indium, stainless steel, or an alloy thereof is used. Among these, aluminum or aluminum alloy is preferable from the viewpoints of potential resistance, high conductivity, and cost. Examples of the positive electrode base material include a foil and a vapor deposition film, and the foil is preferable from the viewpoint of cost. Therefore, the positive electrode base material is preferably an aluminum foil or an aluminum alloy foil. Examples of aluminum or aluminum alloy include A1085P, A3003P and the like specified in JIS-H-4000 (2014).

The lower limit of the average thickness of the positive electrode substrate is preferably 5 μm, more preferably 10 μm. The upper limit of the average thickness of the positive electrode substrate is preferably 50 μm, more preferably 40 μm. By setting the average thickness of the positive electrode base material to the above lower limit or more, the strength of the positive electrode base material can be increased. By setting the average thickness of the positive electrode substrate to be the above upper limit or less, the energy density per volume of the all-solid-state battery can be increased. For these reasons, the average thickness of the positive electrode base material is preferably 5 μm or more and 50 μm or less, and more preferably 10 μm or more and 40 μm or less. "Average thickness" refers to the average value of thicknesses measured at arbitrary ten points. The same definition is applied when the "average thickness" is used for other members.

The intermediate layer is a layer disposed between the positive electrode base material and the positive electrode active material layer. The intermediate layer contains particles having conductivity such as carbon particles, thereby reducing the contact resistance between the positive electrode base material and the positive electrode active material layer. The structure of the intermediate layer is not particularly limited, and includes, for example, a resin binder and conductive particles.

(Cathode active material layer)
The positive electrode active material layer 5 contains a positive electrode active material. The positive electrode active material layer 5 can be formed from a so-called positive electrode mixture containing a positive electrode active material. The positive electrode active material layer 5 may contain a mixture or complex containing a positive electrode active material and a solid electrolyte. The positive electrode active material layer 5 may include optional components such as a conductive agent, a binder (binder), a thickener, and a filler, if necessary. One kind or two or more kinds 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 in lithium ion secondary batteries and all-solid-state batteries. A material capable of inserting and extracting lithium ions is usually used as the positive electrode active material. Examples thereof include a lithium transition metal composite oxide having an α-NaFeO ₂ type crystal structure, a lithium transition metal oxide having a spinel type crystal structure, a polyanion compound, a chalcogen compound, and sulfur. Examples of the lithium-transition metal composite oxide having an α-NaFeO ₂ type crystal structure include, for example, Li[Li _x Ni _1-x ]O ₂ (0≦x<0.5), 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), etc. As the lithium transition metal oxide having a spinel type crystal structure, Li _x Mn ₂ O ₄ , Li _x Ni _γ Mn _{(2 -Γ)} O ₄ etc. Examples of the polyanion 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 chalcogen compounds include titanium disulfide, molybdenum disulfide, molybdenum dioxide, etc. Atoms or polyanions in these materials may be partially substituted with atoms or anion species composed of other elements. The surface of the positive electrode active material may be covered with an oxide such as lithium niobate, lithium titanate, lithium phosphate, etc. In the positive electrode active material layer, one of these positive electrode active materials may be used alone. Well, two or more kinds may be mixed and used.

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 diameter 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 be equal to or less than the above upper limit, the electron conductivity of the positive electrode active material layer is improved.

A crusher, a classifier, or the like is used to obtain the particles in a predetermined shape. Examples of the pulverization 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. Wet grinding in which water or an organic solvent such as hexane is allowed to coexist may be used during grinding. As a classification method, a sieve, an air classifier, or the like is used as needed, both dry and wet.

The lower limit of the content of the positive electrode active material in the positive electrode active material layer 5 is preferably 10% by mass, more preferably 30% by mass, and further preferably 50% by mass. The upper limit of the content of the positive electrode active material is preferably 90% by mass, more preferably 80% by mass. By setting the content of the positive electrode active material within the above range, the electric capacity of the all-solid-state battery 10 can be further increased.

When the positive electrode active material layer 5 contains a solid electrolyte, the lower limit of the content of the solid electrolyte is preferably 10% by mass, more preferably 20% by mass. The upper limit of the content of the solid electrolyte in the positive electrode active material layer 5 is preferably 90% by mass, more preferably 70% by mass, and further preferably 50% by mass. By setting the content of the solid electrolyte within the above range, the electric capacity of the all-solid-state battery can be increased. When the solid electrolyte according to one embodiment of the present invention is used for the positive electrode active material layer 5, the content of the solid electrolyte according to one embodiment of the present invention in the total solid electrolyte in the positive electrode active material layer 5 is 50 mass. % Or more is preferable, 70% by mass or more is more preferable, 90% by mass or more is further preferable, and substantially 100% by mass is even more preferable.

The mixture of the positive electrode active material and the solid electrolyte is a mixture prepared by mixing the positive electrode active material, the solid electrolyte and the like by mechanical milling or the like. For example, the mixture of the positive electrode active material and the solid electrolyte can be obtained by mixing the particulate positive electrode active material and the particulate solid electrolyte. As the composite of the positive electrode active material and the solid electrolyte, a composite having a chemical or physical bond between the positive electrode active material and the solid electrolyte, mechanically composite the positive electrode active material and the solid electrolyte, etc. Examples of the complex include: The composite is one in which the positive electrode active material and the solid electrolyte are present in one particle, for example, those in which the positive electrode active material and the solid electrolyte and the like form an aggregated state, the surface of the positive electrode active material Examples thereof include those having a film containing a solid electrolyte or the like formed on at least a part thereof.

(Arbitrary ingredient)
The conductive agent is not particularly limited as long as it is a material having conductivity. Examples of such a conductive agent include graphite; carbon black such as furnace black and acetylene black; metal; conductive ceramics. Examples of the shape of the conductive agent include powder and fibrous shapes. Among these, acetylene black is preferable from the viewpoint of electronic conductivity and the like.

As a minimum of content of a conductive agent in cathode active material layer 5, 1 mass% is preferred and 3 mass% is more preferred. As a maximum of content of a conductive agent, 10 mass% is preferred and 9 mass% is more preferred. By setting the content of the conductive agent within the above range, the electric capacity of the all-solid-state battery can be increased. For these reasons, the content of the conductive agent 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.

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

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

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, the functional group may be deactivated by methylation or the like in advance.

The filler is not particularly limited. Examples of the filler include polyolefins such as polypropylene and polyethylene, silica, alumina, zeolite, glass, and alumina silicate.

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

The lower limit of the average thickness of the positive electrode active material layer 5 is preferably 30 μm, more preferably 60 μm. The upper limit of the average thickness of the positive electrode active material layer 5 is preferably 1000 μm, more preferably 500 μm. By setting the average thickness of the positive electrode active material layer 5 to the above lower limit or more, an all-solid battery 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 size of the all-solid battery can be reduced.

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

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

The lower limit of the average thickness of the negative electrode substrate 7 is preferably 3 μm, more preferably 5 μm. The upper limit of the average thickness of the negative electrode substrate 7 is preferably 30 μm, more preferably 20 μm. By setting the average thickness of the negative electrode base material to the above lower limit or more, the strength of the negative electrode base material 7 can be increased. By setting the average thickness of the negative electrode base material to the above upper limit or less, the energy density per volume of the all solid state battery can be increased. For these reasons, the average thickness of the negative electrode base material 7 is preferably 3 μm or more and 30 μm or less, and more preferably 5 μm or more and 20 μm or less.

(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 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 these negative electrode active material layers are the same as the respective optional components in the positive electrode active material layer described above. One or two or more of each of these optional components may not be substantially contained in the negative electrode active material layer.

The negative electrode active material layer 6 includes typical non-metal elements such as B, N, P, F, Cl, Br and I, typical metal elements such as Li, Na, Mg, Al, K, Ca, Zn, Ga and Ge, Transition metal elements such as Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, Ta, Hf, Nb, W, etc. other than the negative electrode active material, conductive agent, binder, thickener and filler. It may be contained as a component.

The negative electrode active material can be appropriately selected from known negative electrode active materials usually used in lithium ion secondary batteries and all-solid-state batteries. A material capable of inserting and extracting lithium ions is usually used as the negative electrode active material. Examples of the negative electrode active material include metal Li; metals such as Si and Sn or metalloids; metal oxides such as Si oxides, Ti oxides and Sn oxides or metalloid oxides; Li ₄ Ti ₅ O ₁₂ ; Titanium-containing oxides such as LiTiO _{2 and} TiNb ₂ O ₇ ; polyphosphoric acid compounds; silicon carbide; carbon materials such as graphite (graphite) and non-graphitizable carbon (graphitizable carbon or non-graphitizable carbon). To be Among these materials, graphite and non-graphitic carbon are preferable. In the negative electrode active material layer, 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 an X-ray diffraction method of 0.33 nm or more and less than 0.34 nm before or after charge/discharge. 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 (002) plane of 0.34 nm or more and 0.42 nm or less, which is determined by an X-ray diffraction method before or after charge/discharge. Say. The crystallite size Lc of non-graphitic carbon is usually 0.80 to 2.0 nm. Examples of the non-graphitizable carbon include non-graphitizable carbon and easily graphitizable carbon. Examples of the non-graphitic carbon include resin-derived materials, petroleum pitch-derived materials, alcohol-derived materials, and the like.

Here, the “discharge state” refers to a state in which an open circuit voltage is 0.7 V or more in a single-pole battery using a negative electrode containing a carbon material as a negative electrode active material as a working electrode and metal Li as a counter electrode. Since the potential of the counter electrode of metal Li in the open circuit state is almost equal to the oxidation-reduction potential of Li, the open-circuit voltage in the above unipolar battery is almost equal to the potential of the negative electrode containing the carbon material with respect to the oxidation-reduction potential of Li. .. That is, an open circuit voltage of 0.7 V or more in the above-mentioned single-pole battery means that the carbon material, which is the negative electrode active material, has sufficiently released lithium ions that can be stored and released during 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 non-graphitizable carbon usually has a property that a graphite structure having a three-dimensional stacking regularity is unlikely to be formed among non-graphitic carbons.

The “graphitizable carbon” refers to a carbon material having the above-mentioned d ₀₀₂ of 0.34 nm or more and less than 0.36 nm. The easily graphitizable carbon usually has a property of easily forming a graphite structure having a three-dimensional stacking regularity among non-graphitic carbons.

The average particle size of the negative electrode active material can be, for example, 1 μm or more and 100 μm or less. By setting the average particle size of the negative electrode active material to the above lower limit or more, 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 be equal to or less than the above upper limit, the electron conductivity of the active material layer is improved. A crusher, a classifier, or the like is used to obtain the particles in a predetermined shape. The pulverization method and the powder classification method can be selected from the methods exemplified for the positive electrode layer, for example.

When the negative electrode active material layer 6 contains a solid electrolyte, the lower limit of the content of the solid electrolyte is preferably 10% by mass, more preferably 20% by mass. The upper limit of the content of the solid electrolyte in the negative electrode active material layer 6 is preferably 90% by mass, more preferably 70% by mass, and further preferably 50% by mass. By setting the content of the solid electrolyte within the above range, the electric capacity of the all-solid-state battery can be increased. When the solid electrolyte according to one embodiment of the present invention is used for the negative electrode active material layer 6, the content of the solid electrolyte according to one embodiment of the present invention in the total solid electrolyte in the negative electrode active material layer 6 is 50 mass. % Or more is preferable, 70% by mass or more is more preferable, 90% by mass or more is further preferable, and substantially 100% by mass is even more preferable.

The mixture or composite of the negative electrode active material and the solid electrolyte may be the above-described 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 lower limit of the average thickness of the negative electrode active material layer 6 is preferably 30 μm, more preferably 60 μm. The upper limit of the average thickness of the negative electrode active material layer 6 is preferably 1000 μm, more preferably 500 μm. By setting the average thickness of the negative electrode active material layer 6 to the above lower limit or more, an all-solid battery 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 size of the all-solid-state battery can be reduced.

[Isolation layer]
The isolation layer 3 contains a solid electrolyte. As the solid electrolyte contained in the isolation layer 3, various solid electrolytes other than the solid electrolyte according to the embodiment of the present invention described above can be used, and among these, a sulfide-based solid electrolyte is preferably used. 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. is there. 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 total solid electrolyte in the isolation layer 3 is 50% by mass or more. Is preferred, 70% by mass or more is more preferred, 90% by mass or more is still more preferred, and substantially 100% by mass is even more preferred.

The isolation layer 3 may contain optional components such as oxides such as Li ₃ PO ₄ , halogen compounds, binders, thickeners and fillers. Optional components such as a binder, a thickener, and a filler can be selected from the materials exemplified for the positive electrode layer.

The lower limit of the average thickness of the isolation layer 3 is preferably 1 μm, more preferably 3 μm. The upper limit of the average thickness of the isolation layer 3 is preferably 50 μm, more preferably 20 μm. By setting the average thickness of the isolation layer 3 to the above lower limit or more, it becomes possible to reliably insulate the positive electrode and the negative electrode. By setting the average thickness of the isolation layer 3 to the upper limit or less, it becomes possible to increase the energy density of the all-solid-state battery.

<Method for manufacturing lithium-ion storage element>
A method for manufacturing a lithium-ion storage element according to an embodiment of the present invention uses a solid electrolyte according to an embodiment of the present invention or a solid electrolyte obtained by the method for manufacturing a solid electrolyte according to an embodiment of the present invention. Preparing at least one of a positive electrode layer, an isolation layer and a negative electrode layer. 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) a positive electrode. Laminating a layer, an isolation layer and a negative electrode layer. The positive electrode layer is produced by the above (1) and (4), the isolation layer is produced by the above (2) and (4), and the negative electrode layer is produced by the above (3) and (4). At least one of the positive electrode mixture, the material for the isolation layer, and the negative electrode mixture contains the solid electrolyte according to one embodiment of the present invention or the solid electrolyte obtained by the method for producing a solid electrolyte according to one embodiment of the present invention. Be done. Hereinafter, each step 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 prepared. The method for producing the positive electrode mixture is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include mechanical milling treatment of the material of the positive electrode mixture, compression molding of the positive electrode active material, and sputtering using a target material of the positive electrode active material. If the positive electrode mixture contains a mixture or complex containing a positive electrode active material and a solid electrolyte, this step, for example, by mixing the positive electrode active material and the solid electrolyte using a mechanical milling method or the like, the positive electrode active material and Making a mixture or complex with a solid electrolyte can be included.

(2) Isolation Layer Material Preparation Step In this step, a material for forming the isolation layer is usually prepared. When the lithium-ion power storage device is an all-solid-state battery, 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 processing a predetermined material by a mechanical milling method. The isolation layer material may be produced by heating a predetermined material to a temperature equal to or higher than the melting temperature by a melt quenching method, melting and mixing both at a predetermined ratio, and then rapidly cooling. Other methods for synthesizing the material for the isolation layer include, for example, a solid-phase method of sealing under reduced pressure and firing, a liquid-phase method such as dissolution and precipitation, a vapor-phase method (PLD), and firing in an argon atmosphere after mechanical milling. Can be mentioned.

(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 prepared. The specific manufacturing method of the negative electrode mixture is the same as that of the positive electrode mixture. If the negative electrode mixture contains a mixture or complex containing a negative electrode active material and a solid electrolyte, this step, for example, by mixing the negative electrode active material and the solid electrolyte by using a mechanical milling method or the like, the negative electrode active material and Making a mixture or complex with a solid electrolyte can be included.

(Lamination 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 forming each layer is not particularly limited. The positive electrode layer is formed, for example, by 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 are pressure-molded. The positive electrode layer, the positive electrode mixture, the separator layer material, the negative electrode mixture, and the negative electrode substrate may be pressure-molded at one time to laminate the positive electrode layer, the separator layer, and the negative electrode layer. The positive electrode layer and the negative electrode layer may be preliminarily molded, and pressure-molded and laminated with the isolation layer.

[Other Embodiments]
The present invention is not limited to the above embodiment, and can be carried out in various modified and improved modes other than the above modes. For example, the lithium-ion storage element according to the present invention may be provided with a layer other than the positive electrode layer, the isolation layer, and the negative electrode layer. In addition, the lithium-ion storage element according to the present invention may include a liquid in one or more of the layers. The lithium ion storage element according to the present invention may be a capacitor or the like in addition to the secondary battery.

<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.

Example 1 Synthesis by Liquid Phase Method Li ₂ S (1.311 g), P ₂ S ₅ (1.242 g) and LiCl (0.474 g) were added to 100 mL of tetrahydrofuran (THF) as an organic liquid, The mixture was stirred at room temperature for 3 hours at a rotation speed of 200 rpm to prepare a raw material liquid. The raw material liquid was heated at 100° C. for 3 hours while stirring at a rotation speed of 200 rpm, and the dried raw material liquid was dried under reduced pressure at 120° C. for half a day to volatilize the organic liquid to obtain a precursor. The obtained precursor was formed into pellets. This precursor was fired by heating at 550° C. for 6 hours to obtain a solid electrolyte of Example 1 represented by the composition formula Li ₆ PS ₅ Cl. Note that all the above steps were performed in an argon atmosphere with a dew point of −50° C. or lower.

[Examples 2-3, Comparative Examples 1-2]
Solid electrolytes of Examples 2 to 3 and Comparative Examples 1 and 2 were obtained in the same manner as in Example 1 except that the composition of the organic liquid used was as shown in Table 1. In Table 1, EtOH represents ethanol. The THF and EtOH used in Examples 1 to 3 and Comparative Examples 1 and 2 were all reagents having a water content of 0.001% by mass or less.

Comparative Example 3 Synthesis by Mechanical Milling Method Li ₂ S (0.437 g), P ₂ S ₅ (0.414 g) and LiCl (0.158 g) were mixed in an agate mortar. The mixture was put into a closed 80 mL zirconia pot containing 160 g of zirconia balls having a diameter of 4 mm. These steps were performed in an argon atmosphere with a dew point of −50° C. or lower. A mechanical milling treatment was performed for 25 hours at a revolution speed of 370 rpm by a planetary ball mill (Model number P-7 manufactured by FRITSCH) to obtain a precursor. In a glove box maintaining an argon atmosphere with a dew point of -50°C or lower, the obtained precursor was pelletized and baked by heating at 550°C for 4 hours to obtain a comparative example represented by a composition formula Li ₆ PS ₅ Cl. A solid electrolyte of 3 was obtained.

[Comparative Examples 4 to 9]
The solid electrolytes of Comparative Examples 4 to 9 were obtained in the same manner as Comparative Example 3 except that the rotation speed and processing time in the mechanical milling process and the firing temperature were as shown in Table 2.

[Evaluation]
(1) Powder X-ray diffraction measurement The powder X-ray diffraction measurement was performed by the above method. As the airtight sample holder for X-ray diffraction measurement, a product name "general-purpose atmosphere separator" manufactured by Rigaku Co. was used.

The solid electrolytes of Examples and Comparative Examples both had a diffraction pattern that could be assigned to the space group F-43m. Tables 1 and 2 show the full width at half maximum (FWHM(311)) and full width at half maximum (FWHM(311)) and (222) planes of the diffraction line showing the (311) plane in the solid electrolytes of Examples and Comparative Examples. The ratio (FWHM(311)/FWHM(222)) with the full width at half maximum of the diffraction line (FWHM(222)) is shown.

(2) Ionic Conductivity The ionic conductivity of the solid electrolytes of Examples 1 to 3 and Comparative Examples 1 to 3 at 25° C. was measured for AC impedance by the method described above using “VMP-300” manufactured by Bio-Lobic. Then asked. Table 1 shows the ionic conductivity of the solid electrolytes of Examples 1 to 3 and Comparative Examples 1 to 3 at 25°C.

(3) Average Particle Size The average particle size of the solid electrolytes of Example 1 and Comparative Example 3 was determined by the above method. The average particle size of the solid electrolyte of Example 1 was 14.52 μm. The average particle size of the solid electrolyte of Comparative Example 3 was 14.84 μm.

(4) Discharge capacity (4-1) Preparation of positive electrode active material LiNbO ₃ precursor was prepared by dissolving niobium ethoxide (Nb(OC ₂ H ₅ ) ₅ ) after dissolving metallic Li in ultra-dehydrated ethanol. A solution was prepared. LiNbO ₃ coating was performed on the particle surfaces of LiNi _0.8 Co _0.15 Al _0.05 O ₂ (NCA) using a rolling fluid coating device (FD-MP-01F) manufactured by Paulec. LiNbO ₃ precursor NCA a 400 ° C. coated with, to prepare a LiNbO ₃ coat NCA by heat treatment for 30 minutes. This LiNbO ₃ coated NCA was used as a positive electrode active material.

(4-2) Preparation of all-solid-state battery LiNbO ₃ coat NCA and the solid electrolyte (Li ₆ PS ₅ Cl) of Example 1 were mixed with LiNbO ₃ coat NCA:Li ₆ PS ₅ Cl=70:30 (mass ratio). Weighed so that These were mixed in an agate mortar, and this mixture was used as a positive electrode mixture.
Into a powder molding machine having an inner diameter of 10 mm, 60 mg of sulfide-based solid electrolyte 75Li ₂ S·25P ₂ S ₅ (LPS) was charged as a material for the isolation layer, and then pressure-molded using a hydraulic press to form the isolation layer. Was produced. After releasing the pressure, 17.5 mg of the positive electrode mixture was charged on one surface of the isolation layer, and an In foil as a positive electrode base material was placed thereon, and pressure molding was performed at 360 MPa for 5 minutes. After the pressure was released, a negative electrode obtained by pasting a metallic Li foil as a negative electrode active material layer on a stainless steel plate as a negative electrode base material was opposed to the opposite surface of the isolation layer, and pressure molding was performed at 120 MPa for 3 minutes. Thus, a laminated body having a positive electrode base material, a positive electrode active material layer, an isolation layer, a negative electrode active material layer, and a negative electrode base material and having a diameter of 10 mm was obtained. Prepare a rectangular PTFE plate of about 30 mm square having a through hole with a diameter of about 10 mm in the center, place the obtained laminated body in this through hole, and cover the center of the PTFE plate with 2 It was sandwiched between pieces of stainless steel foil. This was housed in an aluminum-metal resin composite film exterior body, and sealed under reduced pressure by heat welding. At this time, each end of the lead terminal made of nickel foil preliminarily attached to each stainless steel foil was led out from the sealing portion of the outer package. Both sides of this exterior body are sandwiched between two PTFE sheets of about 40 mm square, and both sides are sandwiched between two stainless steel sheets of about 60 mm square, and the stainless steel plates are screwed together under the condition that a pressure of 25 MPa is applied to the laminated body. Tightened with. In this way, an all-solid battery including the solid electrolyte of Example 1 was obtained.

The same operation as in Example 1 was repeated except that the solid electrolyte of Example 1 was replaced by any one of Examples 2 to 3 and Comparative Examples 1 to 3, and Examples 2 to 3 and Comparative Example 1 were performed. All-solid-state batteries with solid electrolytes of ~3 were obtained.

(4-3) Charge/Discharge Test A charge/discharge test was performed on the above all-solid-state battery under the following conditions. The charge/discharge test was conducted in a constant temperature bath at 50°C. The charging was performed at a constant current and constant voltage (CCCV) with a charging current of 0.125 mA/cm ² and a charging upper limit voltage of 4.35V. The charge termination condition was set until the charge current reached 0.0625 mA/cm ² . The discharge was a constant current (CC) discharge with a discharge current of 0.125 mA/cm ² and a discharge end voltage of 2.85V. The rest time between charging and discharging was 30 minutes. The discharge capacity at this time is shown in Table 1.

As shown in Table 1, when the solid electrolytes of Examples 1 to 3 having a half-width ratio (FWHM(311)/FWHM(222)) of 0.93 or more and 0.98 or less were used, the discharge capacity was 150 mAh. It was a large value exceeding /g. It can be seen that the solid electrolyte having such a half width ratio can be obtained by the liquid phase method using an organic liquid having an ether content of 40% by volume or more. In addition, comparing the solid electrolytes of Examples 1 to 3 with the solid electrolyte of Comparative Example 3 synthesized by the mechanical milling method, the ionic conductivity of the solid electrolytes of Examples 2 and 3 is higher than that of Comparative Example 3. Despite being an order of magnitude lower, the all-solid-state batteries using them show a large discharge capacity. Furthermore, although the average particle size of the solid electrolyte of Example 1 and the average particle size of the solid electrolyte of Comparative Example 3 are about the same, there is a large difference in the discharge capacities of the all-solid-state batteries using them. From these facts, in the solid electrolytes of Examples 1 to 3, not only the ionic conductivity and the particle size but the crystal orientation represented by the full width at half maximum ratio (FWHM(311)/FWHM(222)) has a good effect. You can see that is being demonstrated.

Further, as shown in Table 2, when synthesized by the mechanical milling method, the full width at half maximum ratio (FWHM(311)/FWHM(222)) is 0.93 or more, even if the conditions are changed within a general range. It was not possible to obtain a solid electrolyte of 98 or less.

In addition, in the raw material liquid of Example 1 using an organic liquid of 100% THF, some of the added components could not be completely dissolved and became cloudy. On the other hand, in the raw material liquid of Comparative Example 2 using an organic liquid containing 100% EtOH, all the components were dissolved to form a transparent solution. Therefore, separately, Li ₂ S, P ₂ S _5, and LiCl were added to THF or EtOH and stirred to confirm the solubility of these. Li ₂ S, P ₂ S _5, and LiCl were all dissolved in EtOH. On the other hand, in THF, Li ₂ S and LiCl were sufficiently dissolved, but P ₂ S ₅ was hardly dissolved. That is, it can be said that the component that remains in the raw material liquid of Example 1 without being dissolved is P ₂ S ₅ . From the raw material solution containing P ₂ S ₅ which remained without such dissolution, when to obtain a solid body to volatilize the organic liquid, the crystal structure of P ₂ S ₅ solid bodies in the prior addition of P ₂ S It is no different from ₅ . Therefore, it can be inferred that the timing of adding P ₂ S ₅ containing a phosphorus source to the precursor before firing does not affect the crystal orientation of the obtained solid electrolyte.

The solid electrolyte according to the present invention is preferably used as a solid electrolyte of a storage element such as an all-solid battery.

DESCRIPTION OF SYMBOLS 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 All solid state battery

Claims (5)

Contains lithium, phosphorus, sulfur, and halogen,
In the X-ray diffraction measurement using CuKα ray, the diffraction pattern has a diffraction pattern that can be assigned to the space group F-43m and shows the (311) plane. A solid electrolyte having a ratio (FWHM(311)/FWHM(222)) to the full width at half maximum of diffraction lines (FWHM(222)) of 0.93 or more and 0.98 or less. The solid electrolyte according to claim 1, wherein the full width at half maximum (FWHM(311)) is 0.130° or more. To prepare a raw material liquid containing an organic liquid containing ether, a lithium source, a sulfur source and a halogen source,
Volatilizing the organic liquid to obtain a solid body, and firing a precursor containing the solid body in this order,
The content ratio of the ether in the organic liquid is 40% by volume or more,
A method for producing a solid electrolyte, wherein the precursor includes a phosphorus source. A positive electrode layer,
An isolation layer,
And a negative electrode layer,
A lithium ion storage element, wherein the positive electrode layer, the isolation layer, the negative electrode layer, or a combination thereof includes the solid electrolyte of claim 1 or 2. Lithium comprising producing at least one of a positive electrode layer, an isolation layer and a negative electrode layer using the solid electrolyte of claim 1 or claim 2 or the solid electrolyte obtained by the method for producing a solid electrolyte of claim 3. Ion storage element manufacturing method.

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